The mechanical tonometer stands out significantly among its electronic counterparts. Having a high accuracy class (error ±3 mm Hg), the device does an excellent job of measuring blood pressure and providing the most accurate result of this measurement. For this reason, mechanical tonometers have received great recognition and a high degree of trust among medical professionals.

Device of mechanical tonometers

A mechanical tonometer consists of: a shoulder cuff, a bulb (air pump), a stethoscope, and a pressure gauge.

Depending on the manufacturer and model, tonometers can have different configurations and accessories: the tonometer can be supplied with a stethoscope built into the cuff, purchased separately or without it at all. Also, for ease of use, some tonometers have a pressure gauge combined with a bulb.

Mechanical tonometer Microlife BP AG1-40

Let us consider the device of a mechanical tonometer in more detail:

Cuff

• Small price.
• High accuracy.
• They fail less often.
• All components are interchangeable.
• Does not depend on power sources.
• Light weight and compact.

Also, mechanical tonometers have one significant drawback– to use a mechanical tonometer, you must have good hearing and a certain skill in measuring blood pressure, otherwise the whole procedure of measuring your blood pressure yourself will not make any sense. However, this problem can be solved if you ask knowledgeable person measure your blood pressure, and at the same time he will show you how to do it correctly.

Comparison of mechanical tonometers

For comparison, we took the most budget models from such well-known manufacturers as CS Medica, Little Doctor, Microlife and A&D.

A budget-type tonometer can be bought for 600–800 rubles, and if you’re lucky, even cheaper. The main difference between budget devices and more expensive analogues is the absence of a stethoscope in the kit, with the exception of the A&D UA-100 mechanical tonometer. However, this is not so important if you already have this medical device in your arsenal. Cuff size different manufacturers– different and in most cases does not have a fixing ring, which may be inconvenient for some users.

When purchasing a mechanical tonometer, pay attention to the quality of the materials from which the device is made. The cuff must be free of protruding threads and crooked seams, made and quality material(for example, nylon), the pear should be soft, easy to press, and in no case should there be cracks on it. The device itself must be verified, so do not hesitate to ask the seller for a document confirming this.

Blood pressure is one of the most important indicators of human health. If it often increases, then this is already a disease, and a large excess of the norm poses a danger to life. Almost half of humanity suffers from hypertension; pressure must be constantly monitored. That's why it's so important to have a blood pressure monitor on hand. Let's figure out what types of tonometers are easy to use and how to choose the best and inexpensive one.

What types of tonometers are there?

A tonometer is special device for measuring blood pressure. The indicators are displayed immediately and provide complete information about the level of blood pressure and heart rate. Any deviations from the norm are manifested by unpleasant symptoms: headache, nausea, dizziness.

The modern market is pleased with various devices for measuring the indicators under consideration. They differ in the range of functions they perform, the accuracy of readings, dimensions and cost.

There are two types of devices: mechanical and electronic. The former are divided into semi-automatic and automatic. Fully automated devices are divided into two subtypes: shoulder-mounted and wrist-mounted. They all differ in type and order of measurement, and also have pros and cons. But automatic models are considered the most accurate and reliable. For home use You can purchase any of them; it is important to consider the functionality of the device, its cost and reliability.

The design of a mechanical tonometer and its operating principle

Mechanical devices are divided into mercury manometers and membrane ones.

How does a mercury manometer work?

Mercury manometer

The very first device for measuring indicators was a mercury mechanical one. Currently, it is practically not used. But it is considered the most accurate device for measuring blood pressure. It differs from modern ones by the presence of a mercury scale. Its column rises to the required number - this is blood pressure. The remaining devices do not differ from modern ones: a cuff attached to the shoulder, a pump for supplying air, a phonendoscope for capturing tones. The device is unsafe - if you move it carelessly, the scale with mercury can fall out and break, and the toxic liquid can spread across the floor. Therefore, this device was no longer used.

How does a mechanical membrane tonometer work?

Its operation is due to the presence of a sensitive part - a membrane. This is a flexible plate that bends under pressure and, under the influence of additional mechanisms, moves the needle on the pressure gauge scale. The device quite accurately displays the health status indicator, is safe and has a wide range of applications. It is considered a professional tonometer; all medical institutions are equipped with it. For correct use skills are needed, medical personnel are trained in them. At home, it is difficult to measure blood pressure on your own; the main difficulty lies in listening to tones.

Mechanical tonometer

The measuring procedure is as follows:

1. Place the cuff on the forearm, slightly above the bend of the elbow.
2. Place the phonendoscope on the vessel in the bend area.
3. Inflate the cuff with air using a bulb.
4. Gradually releasing air from the cuff with a special valve, listen to the tones and look at the arrow.
5. The first “knocks” are systolic pressure.
6. The final ones are the diastolic indicator.

Modern manufacturers simplify the design of the device. There are models with a phonendoscope inserted into the cuff. And some have a pear combined with a scale.

The advantages are listed by the following factors:

• low cost;
• high measurement accuracy;
• simple device and durability of use.

The disadvantages of the device include:

• measurement requires special skills, keen hearing and good vision;
• it is difficult to measure without outside help, otherwise the indicators will be distorted;
• no additional features.

For home use, it is better to purchase another type of tonometer.

About electronic devices

Electronic devices are divided into semi-automatic and automatic. The principle of operation is similar, but there is a difference in use.

How does a semi-automatic blood pressure monitor work?

Semi-automatic blood pressure monitor

This type of device also has a bulb and cuff, but instead of a scale there is an electronic screen and buttons for control. It is quite similar to a mechanical device, but simpler to operate. You need to use a pear to fill the cuff with air, and then wait until the tonometer itself processes the signals and displays the indicators in large numbers on the display.

The tonometer operates from electrical network or battery powered. The device is compact, quite accurate in readings and equipped with additional functions.

The advantages of the device include the following features:

• good accuracy, error up to 3 mm Hg. st;
• average cost;
• no need to listen to “knocks” and follow the pressure gauge needle;
• compact, easy to carry with you;
• it contains few electronics and reduces the risk of breakdowns;
• equipped with functions such as heart rate detection and the ability to remember the time of the previous measurement.

The device also has negative sides:

• supplying air with a pear increases the risk of distortion in measurements, which is especially difficult for elderly people;
• there is a need to replace batteries; their discharge usually happens at the wrong time;
• There are also breakdowns that require repair in a workshop.

But it is still the most popular tonometer used in everyday life.

Electronic tonometer: what are its operating principles?

This is the most expensive device of all types of tonometers. The kit includes a cuff and an attached electronic device. As soon as the cuff is put on the forearm and the button is pressed, the electric pump built into the device pumps air into it. The entire measurement process takes place automatically, the sensors process the indicators and display them in a digital image on the display screen. Tonometers are quite fragile and require careful handling. Easy to use and have small sizes. There is no need to ask for outside help, but just sit comfortably and relax. Can work from mains or batteries.

Automatic blood pressure monitor

Advantages of an electronic tonometer:

• they can measure blood pressure correctly, reducing the risk of incorrect readings;
• measurement error – 3-5 mm Hg. st;
• the procedure is quite simple and accessible to older people;
• small-sized device.

But the newest model of tonometers also has disadvantages:

• high price;
• presence of error;
• short service life.

New models of automatic tonometers have many different functions that allow you to track not only blood pressure. It is necessary to list only the most popular and widespread:

• the device reminds you of the time of previous use;
• presence of arrhythmia indicator;
• presence of an indicator of correct fastening of the cuff;
• shows the average result of several measurements;
• automatically turns off after finishing work.

There are other functions such as a calendar, clock, cuff inflation indicators and many others.

Electronic blood pressure monitor with wrist mounting

Among the electronic tonometers there is a model that measures pressure on the wrist. This device does not have a cuff, but is simply attached to the wrist, and indicators are displayed on the screen. For them to be accurate, having secured the device in place, you need to sit down and relax, holding your hand with the tonometer at chest level.

Wrist device

This model shortens the time needed to measure blood pressure and is ideal for athletes because they can monitor their readings during training. True, there is a drawback - this is a high error during the exercises. Doctors recommend using this model for people under 40 years of age. In the older generation, the vessels wear out, especially in the wrist area, which reduces the reliability of measurements.

Pros of a wrist tonometer:

• light weight and dimensions, you can carry it with you everywhere and always;
• easy to use, you don’t even need to undress;
• the ability to take measurements anywhere and even on the run;
• no need to select a cuff;
• has many functions available to a conventional automatic tonometer.

Disadvantages of a wrist tonometer:

• there are restrictions on use based on age;
• a very fragile device that requires careful use;
• when moving, it shows results with a large error;
• high price.

Buying this type device, it is necessary to take into account the listed disadvantages and limitations.

How to choose the best one

Knowing what types of tonometers there are for measuring blood pressure, all their advantages and disadvantages, you can quite easily choose a device to use at home. Before you make a purchase, you need to know some nuances:

• What diseases does the patient have? The frequency of use of the device and its adaptation to the disease depend on this.
• Can the patient learn to use different types of devices?
• Price policy.

It is important to first decide which device you need: by operating principle or by installation location. Buy at a pharmacy or specialty medical equipment store. First you need to check whether there are instructions in your native language, a warranty card, and a verification mark.

You also need to inspect the device for build quality, how all the parts are fitted, and the ease of opening and closing the battery compartment. Check all additional functions and ask your sales consultant to make the settings.

A mechanical tonometer guarantees the accuracy of pressure measurements and has a low cost, but it must be operated by a person with good hearing and able to learn how to operate the device. For elderly people who control their condition themselves, only an automatic tonometer is suitable. He does everything himself; he doesn’t even need to waste effort on inflating the cuff. If the patient has had a stroke or heart attack, or has arrhythmia, he must have the function of intellectual sensitivity.

Most purchased brands

The most popular brands of blood pressure monitors are manufactured by Japanese diversified corporation Omron, AND and Japanese high-tech brand Citizen. Tonometers from the Swiss corporation Microlife and the American company Meditech are also in great demand. The following companies are also in demand: Japanese – Nissei and English – B. Well.

List of popular brands

Among the most popular mechanical models are:

• WM-61, B. Well – good accuracy and quality of the pressure gauge. The price is low - 780 rubles.

Mechanical tonometer model WM-61, B. Well

• Microlife BP AG 1-40 – large pressure gauge and cuff size. Has high accuracy of readings. The cost is affordable - 1890 rubles.

Tonometer model Microlife BP AG 1-40

• Ri-Can 141 is an improved model for individual use. Provides maximum accuracy. The price is high - 5950 rubles.

Among semi-automatic ones:

• Microlife BP N1Basic – improved quality and accuracy of the research results. The price is low - 1450 rubles.
• Omron S1 is a reliable device with multiple functions. average price– 1640 rubles.

Semi-automatic model Omron S1

• B. Well WA-22H - excellent accuracy and build quality, improved design, additional design conveniences. Low price - 1690 rubles.

Tonometer model B. Well WA-22H

The best automatic models:

• Microlife BP A2 Basic is a high-quality universal device for the whole family. The price is average - about 3 thousand rubles. Has numerous functions.
• Omron M2 Basic with adapter – reliability of readings and comfort during operation. They can measure the indicators once, and this will be the correct result. average cost– 2450 rubles.

Omron M2 Basic with adapter

Cardiologists advise that for those over 40, it would be better to purchase a machine with a cuff attached to the shoulder. For young people, blood pressure can also be measured using the wrist.

It is necessary to purchase a suitable tonometer for individual use, taking into account all the characteristics of the person, his illnesses, age, need for various functions. Patients with hypertension and stroke survivors especially need the device to monitor blood pressure and prevent complications.

Question: What is a tonometer and for what purposes is it used?

Question: What types of tonometers are there? What are the main differences?

Automatic blood pressure monitors are a more modern development. In such models, air is pumped into the cuff using a compressor by pressing a button. An example is the AND 777 AC tonometer. In semi-automatic blood pressure monitors, air is pumped manually using a “pear”.

As for the forearm models, the measurement with their help is made (the cuff is applied) to the forearm. This type can be clearly illustrated by the Microlife BP A100 Plus tonometer.

Wrist blood pressure monitors are used to measure arterial blood pressure at the wrist. An example is the Nissei WS 820 tonometer.

Our company (online store www.site) offers a wide range of high-quality tonometers from the world's leading brands. Both forearm and wrist models are presented, as well as accessories for tonometers.

Question: Which tonometer should you prefer: forearm or wrist? Help me make a choice!

The choice of tonometer depends entirely on your age and individual characteristics body. For elderly people, as well as people with serious illnesses and sedentary people, we recommend purchasing a forearm tonometer, since most models have no age restrictions and are most suitable for use in hospital settings.

For active and energetic people who are constantly on the move, we recommend choosing a wrist tonometer. Wrist models are compact, lightweight, easy to transport and can easily fit into a handbag or even a clothing pocket. At the same time, in normal conditions they are no less accurate and reliable than forearm ones.

Question: Are automatic blood pressure monitors really that accurate?

If you take the measurement correctly, the maximum error of automatic tonometers is +/-3 mm. rt. Art. It is the incorrect use of the tonometer that, as a rule, causes inaccuracy. Use the tonometer according to the instructions.

Question: I am an elderly man, over 60, but I want to buy a wrist tonometer, a compact device. After all, as far as I know, some models of wrist tonometers also have no age restrictions.

You are absolutely right, some models of wrist tonometers really do not have age restrictions. However, we still do not recommend purchasing wrist blood pressure monitors for older people. This is due to the fact that with age, the vessels on a person’s wrist lose elasticity. This causes a more significant measurement error.

When ordering, be sure to contact our specialists. they will provide you with professional help and will help you decide on the choice of device, as well as make sure that the selected model is compatible with a children’s cuff.

Question: I need a blood pressure monitor as a gift for my husband, but he has a very large hand and a standard cuff will not work. What are the options?

We have models with a cuff for large (L) and extra large (XL) hands. For example, AND 777 AC-L tonometer, or OMRON tonometers with fan-shaped cuffs with a diameter of up to 42 cm. Contact us for advice and assistance in choosing a model individually for your spouse.

Question: Do more expensive models really give more accurate measurements?

All models of tonometers presented in our assortment are products of leading world brands and are of high quality. The difference in price is usually due to the range of functions performed by the device. Choice in in this case should be done based on your individual needs, and not on the price of the device.

If you are in doubt about your choice, contact our consultants for help and remember: one of essential principles Our company is customer-oriented and long-term cooperation, but not immediate profit.

Question: If the device does not suit me, can I return it or exchange it for another model?

The tonometer is a medical device and has direct contact with the human body. In accordance with Art. 25 of the Law of the Russian Federation "On the Protection of Consumer Rights" and Decree of the Government of the Russian Federation dated January 19, 1998 No. 55, in order to comply with sanitary and hygienic requirements, medical instruments, devices and equipment of proper quality are NOT SUBJECT to return or exchange for a similar product (of a different design, model, size, etc.).

We work strictly in accordance with current legislation, therefore we do not have the right to accept the purchased device back or replace it with another model. If you are in doubt about your choice, we kindly ask you to contact our company for professional advice and assistance in choosing a device.

Question: Which device is right for me? Which model do you recommend?

The choice of model depends on many factors and a clear answer, just as there is simply no universal model that would suit absolutely everyone. A lot depends on the individual characteristics of your body. Contact our specialists, and you will certainly be provided with qualified advice and will select a device individually to suit your needs and characteristics.

Question: I do not like the color and design of the tonometer I purchased. I want it back.

Considering the fact that the tonometer belongs to the category of medical equipment, Article 25 of the Law of the Russian Federation “On the Protection of Consumer Rights” and Decree of the Government of the Russian Federation dated January 19, 1998 No. 55 prohibit us from accepting the device from you, as well as exchanging it for a similar one of a different color and design. Our company operates in full compliance with current legislation.

Returns and exchanges of goods are possible only in case of manufacturing defects. We kindly ask you to discuss details regarding color, size, design, as well as technical characteristics of the device in advance in order to avoid unpleasant misunderstandings.

Question: What is the guarantee that I will purchase an original, high-quality tonometer, and not a counterfeit at the price of the original?

One of the most important principles of our company is real assistance to the client and long-term cooperation. We are not interested in making instant, easy profits at the cost of deceiving customers and giving us a bad reputation. Our company has been working in this field for several years and does not change the high standards of quality of products sold and customer service.

We work only with reliable and trusted suppliers of world-famous brands. All products are imported legally, customs cleared and certified.

When purchasing goods, we provide the entire package of accompanying documentation: cash receipts, invoices, invoices (for non-cash payments), as well as copies of certificates, registration certificates and sanitary and hygienic characteristics. Documents are sealed with signatures and original seals.

Question: I need a blood pressure monitor. But I live far from Moscow, and there is no representative office of your company in my city. You work on a 100% prepayment basis. Where is the guarantee that after payment I will receive the device in proper condition? And will I even get it?

We work reliably and with high quality, and therefore we have confidently maintained our position in the market of medical and health products for several years and value our reputation. To pay for the goods, we will send payment receipt and an account containing our data. If necessary, we conclude an agreement in 2 copies. All documents are sealed with our seals and the signature of the general director of the company.

In addition, all devices undergo mandatory testing before shipment, and delivery is carried out only by reliable transport companies and delivery services proven by long-term cooperation.

Question: I've heard about the Dual Check System function on Omron tonometers, but I don't quite understand what it is. Clarify please!

You're right. Indeed, Omron brand tonometers use the so-called Dual Check System, that is dual system control of measurement results. Its essence lies in the fact that two sensors are installed in the device, as a result, two measurement results are compared and compared, and the user sees the more accurate one.

In addition, if the sensor readings diverge by more than 40%, the user receives a message indicating a device malfunction. Examples of models with the Dual Check System function are Omron M6 tonometer and Omron M6 Comfort tonometer.

Question: What is Intellisense technology? I've heard the name many times, but I still don't have an exact idea. In what devices is it used? Tell!

Intellisense technology is used in tonometers from Omron. Its meaning comes from the name: intelli- (intelligent) - “smart” (translated from English) and sense - from English. "feeling", "sensation". That is, this is a kind of “electronic brain” of the device, which allows, based on the user’s sensations, to pump air into the cuff to the optimal level in order to obtain the most accurate result, while avoiding “pumping” of the cuff, which is accompanied by painful sensations.

A similar function is also found in automatic tonometers from other companies under other patented names: FuzzyLogic - in tonometers of brands and, Intellitronics - in tonometers of the brand, IQ System - in.

Question: I have arrhythmia. Does this affect the measurement results in any way? Are there models of tonometers that can diagnose and take into account arrhythmia in the process of measuring pressure?

Yes, arrhythmia affects the measurement results. Unfortunately, it negatively, that is, distorts them. However, there are devices that can diagnose arrhythmia and correct measurement results taking into account the fact of its presence. Prominent representatives of such devices are the Omron M6 tonometer and the Omron M6 Comfort tonometer.

Question: What is the measurement error of the tonometer models presented in your store?

All models of tonometers presented in our store are fully automatic. Their error is +/-3 mm. rt. Art. The error can increase significantly if the tonometer is used incorrectly (non-compliance with operating rules), as well as wrong choice models (large cuff with standard size hands, a wrist model for an elderly person, a device without arrhythmia indication for a person with arrhythmia, etc.).

Please, before purchasing, contact our specialists for qualified advice, and before use, carefully read the instructions and strictly follow them.

Question: How to use a tonometer correctly to achieve the most accurate measurement results?

To achieve the most accurate results, it is important to choose the right tonometer model, taking into account the individual characteristics of your body and strictly follow the instructions for use. Both the forearm cuff and wrist blood pressure monitor should be at heart level. Failure to comply with this simple rule is fraught with significant distortion of measurement results.

The principle of communicating vessels, familiar to us from school course physics. If the cuff or wrist blood pressure monitor is located below or above the level of the heart, this principle is violated, which entails incorrect readings from the devices. Some models of tonometers are equipped with a sensor for the correct position of the hand, and the measurement begins only in the correct position, which guarantees an accurate result.

Question: What is the Fuzzy algorithm for?

The Fuzzy algorithm automatically selects the cuff inflation pressure. Using the Fuzzy algorithm, the device itself determines the required level of inflation pressure based on the individual characteristics of the person. Thanks to the Fuzzy algorithm, the tonometer is easier to use and the measurement is faster and more accurate.

Question: I'm afraid the cuff will be too small for me.

If the cuff does not fit the size of your arm, the accuracy of the measurement may decrease. It is impossible to predict the error in this case. We have extra cuffs different sizes. We will help you choose it.

Question: Instead of results I see an error message, why is this happening?

This can happen if the cuff is not inflated to required pressure, poorly secured, extraneous sounds are heard. Check whether you are putting the cuff on correctly, whether it is securely fastened, check the instructions.

Question: The air from my blood pressure monitor's cuff suddenly deflates.

Perhaps it's the batteries. Or, if you connected the tonometer to the network, then this adapter could be faulty. The bladder in the cuff may be leaking. Contact the service center.

Question: Batteries run out often and quickly. What's happened?

In automatic blood pressure monitors, the compressor requires a large current. Use quality batteries. Replace all batteries at the same time.

Question: My blood pressure monitor is underestimating my blood pressure. What do you recommend doing?

If you have a semi-automatic device, then look at the volume of your hand. The pressure relief valve in the semi-automatic tonometer is adjusted to the average size of an adult’s hand, from 23 to 32 cm.

If the volume of your hand is very different from the average, the etch rate in the upper pressure range is not correct. Use the cuff more suitable size and with an adjusted pressure relief valve.

Check that the cuff is on correctly. Read the original instructions.

Question: Are there any peculiarities in measuring blood pressure in obese people?

Yes, sure. You will probably need a larger cuff for this. To obtain accurate measurement results, it is necessary that the length of the cuff's pneumatic chamber be at least 80% of the circumference of the arm on which the measurement is taken. The width of the cuff should be about 40% of the arm circumference.

In electronic semi-automatic devices, as a rule, when replacing a cuff with a cuff of a different size, it is necessary to adjust the bleed valve. The principle of adjusting the exhaust valve depends on the specific model and is specified in the instructions for the device.

It must be remembered that most electronic tonometers for individual use are designed for an adult with an average body size. For obese people, it would be more correct to use mechanical blood pressure monitors with a properly selected cuff. If you use a short or narrow cuff, this may result in higher readings.

Question: What conditions must be met to fulfill warranty obligations?

The warranty does not apply to products that have failed and/or become defective due to:

Improper use;
. careless use leading to mechanical damage;
. modifications; opening and/or repair by an unauthorized organization (private person);
. violation of the rules of operation, and/or storage, and/or transportation;
. actions of third parties or force majeure.

The warranty does not apply to batteries for electronic devices. To receive warranty service, you must submit: a warranty card, a document confirming payment for the goods (cash receipt), and the purchased goods. Warranty cards that are not completed or not completely filled out by the seller, with erasures or corrections, will not be accepted.

Question: Should I exchange the product for a similar one?

In accordance with Art. 25 of the Law of the Russian Federation "On the Protection of Consumer Rights" and Decree of the Government of the Russian Federation dated January 19, 1998 No. 55, in order to comply with sanitary and hygienic requirements, medical instruments, instruments and equipment of proper quality are NOT SUBJECT to return or exchange for a similar product (other design, model, size, etc.).

Question: I submitted the device for warranty repair, should I be provided with a similar device during the repair period?

According to Article 19 of the Law of the Russian Federation “On the Protection of Consumer Rights” and Decree of the Government of the Russian Federation dated January 10, 1998 No. 55, in order to comply with sanitary and hygienic requirements, similar goods are NOT PROVIDED to the buyer for use during the period of repair of electronic medical devices.

Question: With each subsequent measurement, the tonometer shows different results.

A person’s blood pressure is constantly changing (with almost every contraction of the heart) and never remains the same. It is for this purpose that some modern tonometers have a function for calculating the average pressure value based on the results of the last 3.

Here is just a small and incomplete range of factors influencing changes in pressure: time of day, temperature, stress, frequency of measurements, eating, drinking coffee, smoking, drinking alcohol, anxiety.

Question: Why and what interval should be observed between measurements?

Question: Tell me, how many measurements will a set of batteries last for me?

Depending on the type of tonometer and model of the device, one set of batteries for an automatic tonometer can last from 120 to 1500 measurements. Please remember that the supplied batteries are intended to test the performance of the device and may have a shorter service life than recommended alkaline batteries. More detailed information For specific types of tonometers, please contact our consultants.

Question: I purchased a tonometer from you. It worked great, but my little irresponsible daughter dropped it into a bowl of water (the dog pushed it off the shelf and the device hit the floor). Now the device began to malfunction. Can you replace the device, since it’s not my fault that it broke?

We understand and sympathize with you, but, unfortunately, there is a malfunction due to the fault of the buyer. Please store the device in places inaccessible to children and animals, and treat the device with care. According to the Consumer Rights Protection Law, we do not have the right to accept your device or replace it with a similar one. Exchanges and returns are possible only in case of manufacturing defects.

You can contact the service center (contact details are indicated in the warranty card) and carry out repairs on their terms, since the warranty, unfortunately, does not apply to your case. *Note: Omron blood pressure monitors are shockproof, which has been proven in tests.

Question: My device is faulty. I measured the pressure twice, the third time it simply did not turn on. What should I do?

Most likely, there is a manufacturing defect (although this happens extremely rarely, since all tonometers undergo repeated verification). You need to contact the service center to conduct an independent examination (contact details of the service center are indicated on the warranty card).

You can give the device to us, or you can contact us yourself. The second option will be more effective, since service centers process applications from individuals much faster than from organizations. In addition, you have the right to be present during the examination.

If it is established that there is a manufacturing defect, we will return the amount paid and accept the faulty device, or (at your request) replace it with a similar working one in accordance with the Consumer Rights Protection Law.

Question: My device constantly shows different results. It may be faulty. Or am I doing something wrong? Help me figure it out, please!

This is quite natural, since a person’s blood pressure constantly changes under the influence of various factors that influence the body (for example, weather changes and stressful situations).

If you still doubt the readings of the device, do the following: carefully check whether the device is connected correctly; check the instructions and follow them strictly. You can also contact our consultants for help.

If the problem cannot be resolved, please contact the manufacturer's service center. The address and contact details are indicated in the warranty card.

Question: I purchased a tonometer from your store for personal use. Works great. I want to purchase several devices for the hospital where I work. Can I count on any special conditions(discounts, gifts)? Is cashless payment possible?

Thank you for your positive feedback about the quality of the product! We are glad that you liked the device. Of course, as our regular customer, especially when purchasing several products of the same name, you have the right to count on special conditions.

When purchasing several units of the same product, it is possible to provide a monetary discount. Also, when purchasing many models of tonometers, we give our customers pleasant and useful gifts. In addition, if the amount of your order is large enough, we are ready to deliver the goods to you free of charge throughout Moscow, the Moscow region, as well as to most settlements of the Russian Federation.

When placing an order, please mention that this is not the first time you have contacted us, and we will negotiate the terms of the discount, as well as the possibility of free delivery. Our company works both in cash and by bank transfer.

Question: In what cases is the choice of a wrist tonometer justified?

Wrist blood pressure monitors are generally recommended for people under 40 years of age. This is due to the fact that the arteries in the wrist are thinner than the arteries in the shoulder, and therefore the pulse and blood pressure in the vessels are less visible. In addition, with age, thickening and hardening of artery walls is observed. Therefore, in people over 40 years of age, distortion of readings when measuring pressure on the wrist is possible, and it is not recommended for them to purchase such a device.

Wrist blood pressure monitors are also suitable for people who lead an active lifestyle and play sports. The peculiarity of such devices is their compact size and light weight (80-140g); they are convenient to take with you anywhere. In addition, they can be used to monitor your heart rate during exercise.

Question: What is a WHO pressure indicator in tonometers and why is it needed?

The global standard for blood pressure is the World Health Organization classification, created in 1999 with the joint participation of experts from the World Health Organization (WHO) and the International Society of Hypertension (ISH) based on large-scale studies.

Most of the automatic blood pressure monitors presented in our online store are equipped with a color WHO classification scale and a WHO indicator, which, after measuring blood pressure, shows in which area of ​​the scale the given readings are located and to which blood pressure category they can be classified. This information will help you pay attention in time to taking the necessary measures to normalize your blood pressure or tell you that you should not postpone a visit to the doctor if your readings fall into the dangerous “red” zone.

Question: In addition to measuring blood pressure, what can a tonometer help with?

Almost all tonometers presented in our online store have an arrhythmia indicator, which notifies of violations of the normal frequency or periodicity of heartbeats during measurement. If the indicator appears too often when measuring blood pressure, you should consult a doctor, since arrhythmia is dangerous even with normal blood pressure values.

Question: Are automatic wrist blood pressure monitors as accurate as automatic arm blood pressure monitors?

The principles of measuring pressure in tonometers on the shoulder and on the wrist are essentially similar. If you measure with a wrist blood pressure monitor correctly, keep your arm in the correct position, and do not use the blood pressure monitor on people over 40 or with a weak pulse, then you can expect readings that are as accurate as if you measured with an automatic upper arm blood pressure monitor.

Question: What are the pros and cons of automatic blood pressure monitors?

The strengths of automatic tonometers, of course, include ease of use. The whole process is started by pressing just one button without any effort on pumping air on the part of a person. In addition, the undoubted advantage of automatic tonometers over other types of tonometers is their functionality. Many additional options will help you timely diagnose deviations in your health, use the automatic mode to take three measurements in a row, save data with the date and time of the measurements, and in some models even display them on a computer and print them out.

In addition to the options mentioned, each model has its own unique features, about which our consultants will tell you in more detail. In addition, you can choose blood pressure monitors with stylish design. The most important feature, of course, is the high accuracy of automatic tonometers.

However, the accuracy of the tonometer is influenced by many factors: electromagnetic radiation, hand movements, correct posture, the presence of diseases and whether the person is in a calm, relaxed state. Factors such as these may reduce the accuracy of the readings. To prevent this from happening, take blood pressure measurements using automatic tonometers strictly according to the attached instructions. Another disadvantage is the high price of the device compared to other types of tonometers.

Question: How often and where to check the automatic tonometer?

The recommended period for checking an automatic tonometer is every two years. However, if there is any suspicion that your blood pressure monitor has stopped functioning correctly, you can get checked at any time. service center, whose address and telephone number are indicated in the warranty card. If you cannot find this information, contact our consultants and they will tell you the address and telephone number.

Content

Introduction 4

1 Purpose and scope 5

2 Technical characteristics of Device 6

3 Review of existing solutions and rationale for choosing a structure 7

3.1 Review of existing solutions 7

3.1.1 Automatic blood pressure monitor Omron, M10 IT 10

3.1.2 Semi-automatic tonometer M1 Plus 11

3.1.3 Mechanical tonometer LD-81 12

3.2 Justification for choosing the structure of the control device 13

3.3 Description of the operating principle of the tonometer according to the functional diagram 14

^ 3.4 Model development 17

4 Block diagram and description of individual components 24

4.1 Block diagram 24

4.2 IR emitter AL107A 32

4.3 Photocell FD256 33

4.4 OS series KR(KF)1446UDxx 35

^ 4.5 Liquid crystal module MT–10S1 40

4.6 Microcontroller ATmega128 42

4.7 Level converter DS275 48

4.8 Stabilizers LM78L05 and LM78L12 50

4.9 Calculation of filters 52

5 Development of an algorithm diagram and control program 56

^ 5.1 Main function algorithm 56

5.2 Algorithm of the initialization function 57

5.3 Algorithm of the pulse wave reading function 58

5.4 Algorithm for the mean pressure calculation function 59

^ 5.5 Algorithm for the systolic pressure calculation function 60

5.6 Algorithm for displaying data on the screen 61

6 Description of the circuit diagram 62

^ 6.1 Description of individual elements 62

6.1.1 Analog circuits 62

6.1.2 Microcontroller 63

6.1.3 Communication devices 63

6.1.4 Power circuit 63

Conclusion 64

Appendix A 65

Appendix B 67

Introduction

Today in modern medicine and everyday life there is an urgent question about new diagnostic tools. An accurate diagnosis is impossible without continuous monitoring of a person’s vital signs, such as blood pressure, pulse rate, body temperature, etc. Unfortunately, at the moment, not all of these parameters can be accurately measured in real time - existing devices are either not accurate enough or the measurement methods invasive, i.e. they can affect the measurement result.

The device can be made using inexpensive existing components, does not require highly qualified personnel, and is suitable for use outside medical institutions.

^

1 Purpose and scope

The designed device is designed to answer a pressing question about new diagnostic tools. An accurate diagnosis is impossible without continuous monitoring of a person’s vital signs, such as blood pressure, pulse rate, body temperature, etc. Unfortunately, at the moment, not all of these parameters can be accurately measured in real time - existing devices are either not accurate enough or the measurement methods invasive, i.e. they can affect the measurement result.

This paper presents a design of a device for non-invasive measurement of blood pressure and heart rate (pulse). Such a device allows you to take readings quite often, and in combination with a computer and data storage means, keep detailed statistics on changes in these readings and thus even predict a possible further deterioration in well-being.

^

2 Technical characteristics of the Device

In progress course work a device was designed to non-invasively measure mean, systolic and diastolic blood pressure, as well as heart rate (pulse).

The device has the following characteristics:

• 
  relatively low production cost achieved by using widely used components;
• 
  high measurement accuracy;
• 
  no influence of the fact of measurement on the result;
• 
  versatility of application;
• 
  flexibility achieved by using standard components and using portable code;
• 
  brilliant idea;
• 
  ease of scaling, the ability to connect additional sensors or other automation devices;
• 
  compatibility with standard interfaces;
• 
  ease of operation;
• 
  ease of code modification and adaptation;
• 
  wide range of operating temperatures.

^

3 Review of existing solutions and rationale for choosing a structure

3.1 Review of existing solutions

Today there are several various devices for measuring blood pressure, but, unfortunately, they work on the principle of pumping air into the cuff, i.e. are invasive measurement tools and cannot be used for continuous monitoring. Noninvasive reading devices also exist, but they are too expensive or inaccurate.

There is a known method for continuous monitoring of systolic blood pressure and an apparatus for its implementation (USA patent N 4030485 dated 06/21/77, MKI A 61 B 5/02), which consists in using a calibration device with a light converter that converts changes in light intensity into changes in the amplitude of the electrical signal, measurements of the light intensity corresponding to changes in the volume of blood in the tissue under the transducer are determined, the amplitude of the differential signal is periodically sampled and the amplitude of the signal corresponding to the reference pressure is summed with it. The amplitude of this signal is proportional to systolic pressure.

The disadvantage of this method is its low information content due to the fact that only systolic pressure is determined.

There is a known method for measuring average pressure using a curve obtained from blood pressure measurements (Germany, application N 0S 3511803 dated October 9, 1986, MKI A 61 B 5/02), which consists in converting the resulting blood pressure curve signal into digital form and on the segment of the blood pressure curve that is less than the respiratory cycle, Min is determined, and in the Min zone there is section F, extending on both sides for at least one cardiac cycle, inside section F the largest amplitude value Max and two threshold values ​​S1 and S2 are determined, corresponding 1/3 and 2/3 of the largest amplitude value A1, A3, which is greater than the larger value of S1. Based on this amplitude value of A1, A3, the next amplitude value of A2, A4 is found, which is less than the threshold value S2. This makes it possible to determine between successive amplitudes A1, A2 - A3, A4 Max 1, Max 2. Based on the measured values ​​between these maxima Max 1 and Max 2, the average pressure is determined.

The disadvantage of this method is its low information content due to the fact that only average blood pressure is determined.

There is a known method and device for indirectly measuring blood pressure (EPO, application 0136212 dated 08/03/83, MKI A 61 B 5/02), which consists in using at least one sensor held with a stop in the fossa, where The pulse is determined with a constant force, which is less than the force created by the diastolic pressure of the blood flow in the radial artery. The maximum and minimum values ​​of the pressure signals are determined, the average value of the ratio of the maximum and minimum values ​​is calculated, the systolic and diastolic pressures are calculated and shown on the indicator.

The closest to the proposed product is a method and apparatus for automatically determining the systolic, diastolic and average blood pressure of a patient (France, application N 2593380 dated 01/27/86, MKI A 61 B 5/02), intended for determining blood pressure non-invasively. The device has an amplification line with two channels, containing an amplifier and a filter in series. Both analog signals coming from the two channels are converted into digital form by an analog-to-digital converter. The monitor has, in addition to the converter, a microprocessor with a program block.

The disadvantages of this method and device are the limited scope of application and low quality of recording due to the use of piezoelectric sensors.
^

3.1.1 Omron automatic blood pressure monitor, M10 IT

The main difference between an automatic blood pressure monitor and a mechanical one is its ease of use. To measure blood pressure using an automatic tonometer, you just need to attach the cuff to your arm and press the button. After a few seconds, the measurement result will appear on the device screen.

Figure 3.1.1.1 Automatic blood pressure monitor Omron M10 IT

Specifications:

• 
  Measurement method: oscillometric;
• 
  Accuracy class: clinically tested;
• 
  Arrhythmia indicator;
• 
  Sound signal;
• 
  
• 
  Cuff size, cm: 22-42;
• 
  Averaging results;
• 
  Measurement accuracy: pressure within +/- 3 mm. Hg;
• 
  Measurement accuracy: pulse within +/- 5% of readings.

^

3.1.2 Semi-automatic tonometer M1 Plus

Semi-automatic blood pressure monitors differ from automatic models in that to measure pressure you must independently pump air into the cuff of the device using a bulb. At this time, the semi-automatic tonometer directly measures blood pressure indicators independently.

The accuracy of blood pressure readings when measured using a semi-automatic tonometer is the same as when used.

Figure 3.1.2.1 Semi-automatic tonometer M1 Plus

Specifications:

• 
  Accuracy class: A/A;
• 
  Arrhythmia indicator: yes;
• 
  Sound signal: yes;
• 
  Memory capacity: 21 measurements;
• 
  Batteries: 4 AA batteries;
• 
  Cuff size, see: 22-32.

^

3.1.3 Mechanical tonometer LD-81

Figure 3.1.3.1 Mechanical tonometer LD-81

Specifications:

Pressure measurement range from 20 to 300 mmHg.

Limits of permissible absolute error of the device when measuring pressure in the cuff at temperatures: from 18° to 33°C to +/- 3 in the range from 60 to 240 mmHg. (up to +/- 4 in other ranges). from 5° to 17° C and from 34° to 40° C to +/- 6.

Operating conditions of the devices: ambient temperature from + 10° C to + 40° C, relative humidity from 30% to 85%, Atmosphere pressure from 86 to 106 kPa, storage and transportation temperature from - 34° C to + 65° C.

Standard cuff size for an adult (shoulder circumference approximately 25 to 36 cm).

The weight of the device is no more than 340 g.
^

3.2 Justification for choosing the structure of the control device

The objective of this product is to develop a method for determining blood pressure based on assessing the shifts of the corresponding points of pulse waves using the proposed device, which would simplify the measurement procedure, improve the quality of pulse wave registration, and expand functionality.

The principle of operation is that a pulse wave is recorded on the radial artery with two optoelectronic sensors, the coordinates of the maximum amplitudes of the pulse waves are measured, the module of the difference in the values ​​of these coordinates is measured, the value of which determines the average arterial pressure, the diastolic blood pressure is calculated from the value of half the difference of triple the average value and systolic pressure, register the first derivatives of these pulse waves, measure the displacement between the maximum amplitudes of the first derivatives of the pulse waves at their inflection points, the value of which is used when determining systolic blood pressure by means of a correction factor.

The diagram of the designed device is described in detail below.

^

3.3 Description of the operating principle of the tonometer according to the functional diagram

Figure 3.3.1 Functional diagram

^

3.4 Model development

A device for non-invasive blood pressure measurement contains two sensors made on optoelectronic elements, two channels of low-pass filters and two amplifier channels, the inputs of which are connected respectively to the outputs of the first and second optoelectronic sensors, two differentiators, an analog-to-digital converter, a microcontroller, a display and a communication port.

Description of the functional diagram of the device shown above: a silicone product equipped with two infrared emitters and two photocells.

The light from the emitters is completely internally refracted, so the voltage at the output of the photocells is zero.

When a pulse wave passes through the artery, the silicone product is deformed, thus, a light flux begins to flow to the photocell, which leads to the appearance of a non-zero voltage at the output of the photocell.

Two identical emitter-receiver pairs are placed along the artery, i.e. the pulse wave observed under each of the sensors is the same wave, shifted in phase.

Due to the semiconductor nature of the photocell, as well as other reasons, there will be high frequency noise present at the output of the photocell. To filter noise, a low-pass filter is provided in each channel, the calculation of which is given below.

After filtering, the signal must be amplified to a level of about 5V. For these purposes, an amplifier based on an operational amplifier chip is used.

The resulting signal, amplified and cleared of noise, is sent to a differentiator, after which 4 signals (2 amplified and the same, but differentiated) are sent to a 10-bit ADC, after which they are processed in the microcontroller. Using established algorithms and formulas, MK calculates average, diastolic and systolic blood pressure and pulse rate.

After receiving the result, it is displayed on the LCD display and transferred for analysis and storage to a PC via a communication port (RS-232)

Figure 3.4.1 Two optoelectronic sensors

Paired optoelectronic sensors 1 and 2 are located on the radial artery. The radiation generated by the radiation source, reflected from the area of ​​the vessel under study, is modulated in amplitude by blood flow pulsations. The modulated flow is converted into an electrical signal in the photodetector. Filtering units and amplifiers filter and amplify the signal. Filtered and amplified pulse wave signals arrive at the inputs of differentiators, where the first derivative of the systolic section of the pulse wave is isolated. The signals received at the outputs of the amplification and differentiator blocks are fed to an analog-to-digital converter. The ADC converts analog signals into the digital form necessary for the operation of the microcontroller.

Figure 3.4.2 Pulse waves and their differential shape

The microprocessor determines the coordinates of the maximum amplitudes of pulse waves and calculates the ∆T value:

∆T = T 1 -T 2 , (1)

T 1 - coordinate of the maximum amplitude of the pulse wave received by the first sensor 1;

T 2 - coordinate of the maximum amplitude of the pulse wave received by the second sensor 2.

The coordinates of the inflection points (max differential shape of the pulse wave) of the systolic section of the pulse wave are also determined and the value ∆T p is calculated:

∆Т p = ∆Т 1 -∆Т 2 (2)

∆T 1 - coordinate of the inflection point of the systolic section of the pulse wave received by the first sensor 1;

∆T 2 - coordinate of the inflection point of the systolic section of the pulse wave received by the second sensor 2.

The value of mean arterial pressure (P avg) is inversely proportional to the value of ∆T:

P medium = F(∆T p). (3)

The value of systolic blood pressure (P syst) is inversely proportional to the value of ∆T p and depends on the stroke volume of the heart:

P syst = F(∆T p). (4)

Diastolic pressure is determined from the formula (P diast):

The statistical modeling of pulse wave processing in accordance with the formula made it possible to determine the exact dependencies for P media with a correlation coefficient of 0.95:

P av = 86.3-0.82∆T for ∆T > 29. (8)

Dependencies for P systems with a correlation coefficient of 0.89 were obtained similarly:

According to the table, which is recorded in the internal memory of the microprocessor, the values ​​of average and systolic blood pressure are selected in accordance with the obtained values ​​of ∆T and ∆T p.

The received data is sent to the internal display and to an external device.

The proposed method for determining blood pressure is simple and not burdensome for the patient, because The measurement time takes no more than 30 seconds.

The device for determining blood pressure is manufactured in the form of an autonomous unit connected by a flexible cable to a sensor unit. It has external connectors for connecting display devices or a PC. In this case, a diagram of the pulse wave of the patient being examined and the values ​​of blood pressure and pulse can be displayed on an external device.

When using the proposed device in conjunction with a PC, it is possible to significantly expand the range of tasks to be solved.

Figure 3.4.3 Example of output of pulse wave speed data

For example, the device, together with a computer and data storage devices, allows you to take readings quite often and keep detailed statistics on changes in these readings and thus even predict possible further deterioration of well-being (Figure 3.4.3).
^

4 Block diagram and description of individual components

4.1 Block diagram

The block diagram shows with the help of which elements the required functionality is implemented.

Figure 4.1.1 Block diagram

Figure 4.1.1 shows the block diagram of the designed device. Let's take a closer look at it.

The domestic photocell FD256, which has the necessary characteristics and a low price, is used as a photodetector. The signal from the photocells is removed and transmitted to low-pass filter microcircuits.

Since the operation of the device requires registration of a pulse wave at two points, naturally the electronic part of the device up to the microcontroller consists of two independent channels, the links of which are completely duplicated.

Low-pass filter – Butterworth filter, implemented on active elements (Figure 4.1.2)

Figure 4.1.2 Schematic diagram low pass filter

Filter options:

Cutoff frequency – 20Hz

Transition region width – 100Hz

R1 - 44.8 kOhm

R2 - 44.8 kOhm

R3 - 22.6 kOhm

A detailed calculation of the filter is given below in the corresponding section of this work.

To demonstrate the performance of the calculated filter, its circuit was assembled in the Proteus environment and simulated. A sinusoid was used as a useful signal model, and a high-frequency sinusoid was used as noise. As can be seen from the graphs, the low-pass filter brilliantly coped with the task for both channels.

Figure 4.1.3 Low Pass Filter Simulation

Figure 4.1.4 Schematic diagram of an inverting amplifier

The output voltage after the photocell is up to 100mV, so to bring the voltage level to 5V, the gain is 50.

This amplifier was built in the Proteus electronics simulation environment. Below are the graphs of its operation for two channels, respectively.

Figure 4.1.5 Simulation for the gain section

Figure 4.1.6 Schematic diagram of an inverting differentiator

To obtain the first derivative of the processed signal, a differentiation link is used, made on an operational amplifier microcircuit.

This differentiator was built in the Proteus electronics simulation environment to demonstrate its functionality. Below are graphs of its operation and a schematic diagram in the Proteus environment.

Figure 4.1.7 Operating schedules and circuit diagram of the differentiator

The four received signals are fed to the ADC input. The built-in 10-bit ADC on the ATmega microcontroller was selected as the ADC. Its speed and capacity are quite sufficient to perform all required operations.

Sampling occurs at a frequency of 20Hz using an interrupt from the built-in timer.

The microcontroller measures vital parameters in the body of the loop in the main program every 5 seconds. The results obtained are displayed on the LCD display.

Display MT-10S1 is a domestically produced 10-character LCD display, described in more detail below.

Also, the received data is sent via the RS-232 port to the computer, where it can be saved, further processed, printed and saved for further analysis.

The DS275 chip is used to match the levels. The DS275, manufactured by Dallas Semiconductor, is a TX/RX line-powered RS232 driver that is fully compatible with standard RS232 implementations.

• 
  
• 
  
• 
  

To power the designed device, widely used voltage stabilizers manufactured by National Semiconductor LM78L05, rated at 5 volts, were chosen. Stabilizers are linear voltage regulators of positive polarity.

All operational amplifiers are domestically produced and High Quality. Their characteristics are discussed in detail in the corresponding subsection below.

^

4.2 IR emitter AL107A

Figure 4.2.1 Appearance of the AL107A IR emitter

Specifications:

• 
  Specifications;
• 
  Maximum reverse voltage 2V;
• 
  Maximum forward current 100 mA;
• 
  Maximum pulse forward current 600 mA;
• 
  Hole mounting;
• 
  Operating temperature -60...85 C;
• 
  Radiation power P 5.5 mW;
• 
  Forward voltage 1.8 V;
• 
  at current Ipr. 100 mA;
• 
  Wavelength 953 nm;
• 
  Emission spectrum width 30 nm;
• 
  Apparent solid angle 15 degrees.

^

4.3 Photocell FD256

Figure 4.3.1 Appearance of photocell FD256

Silicon based photodiode.

Specifications:

• 
  Photosensitive element area (effective) 1.37mm 2;
• 
  Operating temperature 20±5 ºC;
• 
  Operating voltage 10 V;
• 
  Spectral sensitivity range 0.4 - 1.1 microns;
• 
  Maximum spectral characteristics 0.8 - 0.9 microns;
• 
  Dark current no more than 5 nA;
• 
  Integral current sensitivity is not less than 0.02 μA/lx;
• 
  Intrinsic time constant (U = 10 V) no more than 12 ns;
• 
  Own time constant (U = 60 V), no more than 2 ns;
• 
  
• 
  Metal body;
• 
  Sensitivity threshold, no more than 1 x 10 -11 lm x Hz-1/2;
• 
  Electrical insulation density, not less than 180 V;
• 
  Entrance window lens;
• 
  Window material glass C52-1;
• 
  Weight, no more than 1 g;

• 
  Temperature range from –60º C to + 85º C;
• 
  Maximum permissible voltage 90 V;
• 
  Maximum permissible illumination 100,000 lux;
• 
  The failure rate is no more than 3 x 10 -5 h-1 during an operating time of 5000 hours with a confidence probability of 0.6.

^

4.4 OU series KR(KF)1446UDxx

CMOS op-amp structures are extremely cost-effective, have low input bias current, operate from unipolar and bipolar power supplies, and provide rail-to-rail output voltage. Because of the unique topology that makes these characteristics possible, a new Spice Macro Model (SMM) was required to produce accurate results when simulating circuit designs using CAD tools.

A very successful SMM CMOS op-amp was developed by National Semiconductor Corporation, but they do not write models for Russian microcircuits for similar purposes.

Spice model of op-amp series KR(KF)1446UDxx

Product TU Functional analogue	Number of op-amps	Frequency Single Gains	Large signal amplification	Voltage Offsets	Slew rate V/μs	Quiescent current of one op-amp	Power, V
2-channel universal operational amplifier
KР1446UD1A KR1446UD1B KR1446UD1V	2	1,3	80…96	3,0	1,0	1,1	2,5..7,0
2-channel micro-power operational amplifier
KР1446UD2A KR1446UD2B KR1446UD2V	2	0,05	80…96	6,0	0,035	0,013	2,5…7,0
4-channel micro-power operational amplifier
KR1446UD3A KR1446UD3B KR1446UD3V	4	0,05	80...96	6,0	0,035	0,013	2,5…7,0
2-channel low power operational amplifier
KR1446UD4A KR1446UD4B KR1446UD4V	2	0,45	80...96	3,0	0,5	0,14	2,5...7,0
2-channel high-speed operational amplifier
KF1446UD5A KF1446UD5B KF1446UD5V	2	3,6	80...96	3,0	2,7	3,1	2,5...7,0

Spice model of op-amp series KR(KF)1446UDxx Continued

Product specifications Functional analogue	Number of op-amps	Frequency Single Gains	Large signal amplification	Voltage Offsets	Slew rate V/μs	Quiescent current of one op-amp	Power, V
2 Channel General Purpose High Voltage Operational Amplifier
KF1446UD11A KB1446UD11B KB1446UD11V	2	1,3	80...96	3,0	1,0	1,1	3,0...12,0
2 Channel Micro Power High Voltage Operational Amplifier
KF1446UD12A KB1446UD12B KB1446UD12V	2	0,05	80...96	6,0	0,02	0,013	3,0...12,0
4 Channel Micro Power High Voltage Operational Amplifier
KF1446UD13A KB1446UD13B KB1446UD13V	4	0,05	80...96	6,0	0,02	0,013	3,0...12,0
2 Channel Low Power High Voltage Operational Amplifier
KF1446UD14A KB1446UD14B KB1446UD14V	2	3,6	80...96	3,0	2,7	3,1	3,0...12,0

Figure 4.4.1 Distribution of outputs of the op-amp series KR(KF)1446UDxx

Figure 4.4.2 Block diagram of the op-amp series KR(KF)1446UDxx

KR(KF)1446UDxx - a series of CMOS integrated operational amplifiers (OA) with an extended range of permissible input (from -U to +UCC inclusive) and output voltages. The series includes 9 OUs: KR(KF)1446UD1/UD2/UD3/UD4/UD5/UD11/UD12/UD13/UD14.

Amplifiers have a wide range of permissible supply voltages. The supply voltage can be either unipolar (-Ucc>0 or +UCC 0). In any case, the voltage Ucc at the +UCC pin relative to the -Ucc pin can vary from +2.5V to +7V for amplifiers UD1, UD5 and from +3.0V to +12.0V for UD11, UD14.

The KR1446UDxx series provides the ability to select an op-amp with the required quiescent current for one amplifier (10μA-UD2, 3, 12, 13; 100μA-UD4, 14; 0.8mA - UD 1, 11; 2.4mA - UD5), which will provide the optimum for a specific application combination of dynamic and load characteristics of the op-amp with minimal power consumption.

High input impedance (>1000MOm) allows the op-amp to work with high-impedance sources.

The integrated circuit housing houses either 2 identical op-amps (UD1, 11, 2, 12, 4, 14, 5), or 4 0U (UD3, 13). The op-amps in the microcircuits UD2 and UD3, as well as UD12 and UD13 are identical.

Op-amps are intended for constructing small-sized blocks of various devices as amplifiers of direct and alternating current, pulse signals, generators, comparators, etc. Op-amps can be used in the construction of the following types of devices: power supplies, low-frequency active filters, amplifiers with low input currents, hearing aids, microphone amplifiers, picoampermeters, integrators, analog-to-digital automation devices.

Specifications:

• 
  Extended range of input and output voltages (from -Ucc to +UCC);
• 
  Wide range of supply voltages (from 2.5V to 7V and from 3.0V to 12.0V);
• 
  Wide selection of op-amp quiescent currents;
• 
  High input impedance (>1000 MOhm);
• 
  Internal frequency correction;
• 
  Design - 8- and 14-pin plastic DIP or SO package.

^

4.5 Liquid crystal module MT–10S1

The MT–10S1 liquid crystal module consists of an LSI control controller and an LCD panel. The control controller KB1013VG6, manufactured by ANGSTREM OJSC, is similar to HD44780 from HITACHI and KS0066 from SAMSUNG.

The module is available with LED backlight. The module allows you to display 1 line of 10 characters. Symbols are displayed in a 5x8 dot matrix. There are spaces between characters that are one display dot wide.

Each character displayed on the LCD corresponds to its code in the module’s RAM cell.

The module contains two types of memory - codes for displayed characters and a user character generator, as well as logic for controlling the LCD panel.

Figure 4.5.1 Appearance of the MT–10S1 liquid crystal module

The module allows you to:

• 
  the module has software-switchable two pages of a built-in character generator (alphabets: Russian, Ukrainian, Belarusian, Kazakh and English;);
• 
  Work on both 8 and 4-bit data buses;
• 
  receive commands from the data bus;
• 
  write data to RAM from the data bus;
• 
  read data from RAM onto the data bus;
• 
  read state status on data bus;
• 
  display a blinking (or non-blinking) cursor of two types;
• 
  control the backlight.

^

4.6 ATmega128 microcontroller

To control the entire device and exchange data with a PC, the ATmega128 microcontroller manufactured by Atmel was chosen. These micro controllers have a number of advantages over other micro controllers and circuits based on traditional analog and digital components:

• 
  High performance, low power 8-bit AVR microcontroller;
• 
  Advanced RISC architecture:
  • 
    133 powerful instructions, most of which are executed in one machine cycle;
  • 
    32 8-bit general purpose registers + built-in peripheral control registers;
  • 
    Completely static operation;
  • 
    Performance up to 16 million operations per second at a clock frequency of 16 MHz;
  • 
    The built-in multiplier performs multiplication in 2 machine cycles;
• 
  Non-volatile program and data memory:
  • 
    Durability of 128 kB of in-system reprogrammable flash memory: 1000 write/erase cycles;
  • 
    Optional boot sector with separate programmable protection:
    • 
      In-system programming with built-in boot program;
    • 
      Guaranteed dual operation: read-while-write capability;
  • 
    Durability 4 kB EEPROM: 100,000 write/erase cycles;
  • 
    Built-in static RAM with a capacity of 4 kB;
  • 
    Optional ability to address external memory up to 64 KB;
  • 
    Programmable program code protection;
  • 
    SPI interface for in-system programming;
• 
  JTAG Interface (IEEE 1149.1 compliant):
  • 
    Boundary scanning in accordance with the JTAG standard;
  • 
    Extensive support for embedded debugging features;
  • 
    Programming of flash memory, EEPROM, configuration and security bits via JTAG interface;
• 
  Distinctive features peripheral devices:
  • 
    Two 8-bit timer-counter with separate prescalers and comparison modes;
  • 
    Two extended 16-bit timer-counter with separate prescalers, comparison modes and capture modes;
  • 
    Real time counter with separate generator
  • 
    Two 8-bit PWM channels;
  • 
    6 PWM channels with programmable resolution from 2 to 16 bits;
  • 
    Comparison output modulator;
  • 
    8 multiplexed channels of 10-bit A/D conversion:
    • 
      8 unbalanced channels;
    • 
      7 differential channels;
    • 
      2 differential channels with selective gain from 1x, 10x and 200x;
  • 
    Two-wire serial interface, not oriented data transfer in byte format;
  • 
    Two channels of programmable serial USART;
  • 
    SPI serial interface supporting master/slave modes;
  • 
    Programmable watchdog timer with built-in generator;
  • 
    Built-in analog comparator;
• 
  Special features of the microcontroller:
  • 
    Power-on reset and programmable low-voltage reset circuit;
  • 
    Built-in calibrated RC generator;
  • 
    External and internal sources of interruptions;
  • 
    Six modes to reduce power consumption: Idle, ADC noise reduction, Power-save, Power-down, Standby and Extended Standby;
  • 
    Software selection of clock frequency;
  • 
    Configuration bit for switching to ATmega103 compatibility mode;
  • 
    General disabling of pull-up resistors on all lines of I/O ports;
• 
  I/O and Housings:
  • 
    53 – programmable input/output lines;
  • 
    64-pin TQFP package;
• 
  Operating voltage 4.5 - 5.5V;
• 
  Speed ​​gradations 0 - 16 MHz.

The AVR core combines a rich instruction set with 32 universal working registers. All 32 registers are directly connected to an arithmetic logic unit (ALU), which allows two different registers to be specified in one instruction and executed in one cycle. This architecture offers greater code efficiency by achieving 10 times higher performance than conventional CISC microcontrollers.

The ATmega128 contains the following elements: 128 kB of in-system programmable read-while-write flash memory, 4 kB of EEPROM, 4 kB of SRAM, 53 general-purpose I/O lanes, 32 general-purpose working registers, real-time counter (RTC), four flexible timers -counter with comparison and PWM modes, 2 USART, two-wire serial interface oriented to byte transmission, 8-channel 10-bit. ADC with optional programmable gain differential input, programmable watchdog timer with internal oscillator, SPI serial port, IEEE 1149.1 compliant JTAG test interface which is also used to access on-board debug and programming, and six software selectable reduction modes power. Idle mode stops the CPU, but at the same time maintains the operation of the static RAM, timers-counters, SPI port and interrupt system. Powerdown mode allows you to save the contents of registers while the oscillator is stopped and built-in functions are disabled until the next interrupt or hardware reset. In Power-save mode, the asynchronous timer continues to operate, allowing the user to maintain the timekeeping function while the rest of the controller is in a sleep state. ADC Noise Reduction mode stops the CPU and all I/O modules except the asynchronous timer and ADC to minimize impulse noise during the ADC conversion process. In Standby mode, the crystal/resonator oscillator continues to operate while the rest of the microcontroller is in sleep mode. This mode is characterized by low power consumption, but at the same time allows for the fastest return to operating mode. In Extended Standby mode, the main generator and asynchronous timer continue to operate.

The microcontroller is manufactured using high-density non-volatile memory technology from Atmel. Built-in in-system programmable flash memory allows program memory to be reprogrammed directly within the system via the SPI serial interface using a simple programmer or using a standalone program in the boot sector. The boot program can use any interface to load the application program into flash memory. The program in the boot sector continues to run while the application section of the flash memory is updated, thereby maintaining dual operation: read while writing. Due to the combination of 8-bit. RISC CPU with on-chip flash memory The ATmega128 is a powerful microcontroller that offers a high degree of flexibility and cost-effectiveness in the design of most embedded control applications.

The ATmega128 is supported by a full range of software and hardware design tools, including: C compilers, macro assemblers, software debuggers/simulators, in-system emulators and evaluation suites.

Figure 4.6.1 – Pinout layout of the ATmega128 microcontroller
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4.7 Level converter DS275

The DS275, manufactured by Dallas Semiconductor, is a TX/RX line-powered RS232 driver that is fully compatible with standard RS232 implementations.

Figure 4.7.1 – Pinout location of the DS275 chip

The microcircuit was chosen as a level converter because has a number of obvious advantages:

Powered by RX/TX lines of the COM port

Operation in asynchronous full duplex mode

Does not require external elements, such as capacitors, for operation (unlike its analogue - MAX232)

Figure 4.7.2 – Example of switching on the DALLAS DS275 chip

Technical characteristics of the microcircuit:

• 
  Supply voltage – 5/12V;
• 
  Output voltage - ±15V;
• 
  Operating temperature range – 0С…+70С.

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4.8 Stabilizers LM78L05 and LM78L12

Figure 4.8.1 – Pinout location of the LM78LXX voltage regulator

To power the designed device, widely used voltage stabilizers manufactured by National Semiconductor LM78L05 and LM78L12, designed for 5 and 12 volts, respectively, were chosen. Both stabilizers are linear voltage regulators of positive polarity and have similar technical characteristics:

• 
  The output voltage varies by ±5% depending on the temperature (see Figure 4.8.2);
• 
  Output current – ​​up to 100mA;
• 
  Built-in thermal protection;
• 
  Built-in current limiter;
• 
  Available in various packages (TO-92, SO-8, various SMD packages, etc.);
• 
  Does not require external components;
• 
  Output voltage 5 and 12 V.

Figure 4.8.2 – Temperature characteristics of the stabilizer
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4.9 Calculation of filters

Unfortunately, the signal received from photodetectors is noisy. This noise has two components - photon noise and semiconductor noise - and is high-frequency in nature.

To solve the problem of a noisy signal, a low-pass filter was designed, which should be located after each of the photodetectors.

As you know, the maximum heart rate is about 200 beats per minute, i.e. up to 4Hz. To increase the accuracy of measurements, we will take readings 20 times per second, i.e. The cutoff frequency for the low-pass filter will be 20Hz.

Since calculating the filter and component ratings is a simple but painstaking task, during which it is easy to make mistakes, we used special software developed at the Department of Automated Communications Technology to calculate the filter.

Figure 4.9.1 Low Pass Filter Parameters

Figure 4.9.1 shows the parameters of the calculated filter. Since an amplifier is already included in the circuit, the filter does not require additional gain in the transmission region and the gain is set equal to unity.

Figure 4.9.2 Comparison various types filters

It was decided to use a Butterworth filter because... it allows you to get a very smooth frequency response in the gain region (Figure 4.9.2). The flatness of the cutoff line is compensated by the fact that high-frequency noise still starts at a frequency of about 1 kHz, i.e. they will attenuate very strongly.

Figure 4.9.3 Schematic diagram of connecting the filter section

The calculation program proposed a second-order Butterworth filter, which is easy to implement using just one link, shown in Figure 4.9.3.

Figure 4.9.4 Calculated element ratings

Figure 4.9.4 shows the calculated ratings of the filter elements, reduced to the standard rating range.

R1 - 44.8 kOhm

R2 - 44.8 kOhm

R3 - 22.6 kOhm

Figure 4.9.5 Frequency response of low-pass filter

Figure 4.9.5 shows the frequency response of the calculated filter. It is easy to see that the calculated filter fully satisfies the stated requirements.

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5 Development of an algorithm diagram and control program 5.5 Algorithm for the function of calculating systolic pressure

Figure 5.5.1 - Block diagram of the systolic pressure calculation function

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5.6 Algorithm for displaying data on the screen

Figure 5.6.1 - Block diagram of the function of displaying data on the screen
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6 Description of the circuit diagram

In full accordance with the block diagram, below is a description of the individual blocks and elements of the electrical circuit diagram.

The designed device consists of two data channels, a microcontroller with a built-in ADC, an LCD display and a communication port. Each data transmission channel consists of an optocoupler, a low-pass filter, an amplifier and a differentiator.

^

6.1 Description of individual elements

6.1.1 Analog circuits

XP4 – connector for connecting to two optocouplers

Low-pass filters are used to cut off high-frequency semiconductor and photonic noise from the useful signal received from photocells that are part of optocouplers.

R1, R2, R3, R4, C6, C7, DA1 and R10, R11, R12, R13, C9, C10, DA4 – low-pass filters with a cutoff frequency of 20 Hz.

Since the signal received from photocells has an amplitude of only up to 100 mV, signal amplifiers on operational amplifier chips are used to raise the signal level to 5V.

R5, R6, R7, DA2 and R14, R15, R16, DA5 are amplifiers based on operational amplifier chips with a gain of K=50.

To obtain the first derivative of the filtered signal, a pair of differentiating links is used.

R8, R9, C8, DA3 and R17, R18, C11, DA6 – differentiators with time constant T=0.1

6.1.2 Microcontroller

The ADC built into the microcontroller samples 4 received data streams; The microcontroller processes the received data, calculates average, diatolic and systolic pressure, as well as pulse. In addition, the microcontroller produces an indication on the LCD display and transmits the received data to the PC through the communication port.

DD1 – microcontroller with built-in 10-bit ADC

Q1 – quartz resonator with a frequency of 20 MHz

C1, C2 – auxiliary capacitors for the oscillating circuit

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6.1.3 Communication devices

An LCD display is used to inform the user, and an RS-232 communication port is used to transfer data to a PC.

DD2 – voltage level matching chip for the RS-232 port

XP1 – RS232 communication port connector

XP3 - connector for connecting a liquid crystal display

^

6.1.4 Power circuit

The power circuit provides a stable 5V voltage to power all active analog and discrete components of the device.

XP2 – connector for connecting an external power source

DA0 is a voltage stabilizer that provides power to the device with a voltage of 5V.

Conclusion

In this work, a device for non-invasive measurement is designed
blood pressure and heart rate (pulse). Such
the device allows you to take readings quite often, and in total
with a computer and data storage means - maintain detailed
statistics on changes in these readings and thus even
predict possible further deterioration of well-being.
The device can be made on inexpensive existing element base,
does not require highly qualified personnel, suitable for use
outside medical institutions.

During the design of the device, the knowledge and skills acquired over the years of studying the specialty “Automation and Control in Technical Systems” were fully used.
^

Appendix A

The assignment sheet will be inserted here.

And here there will be a calendar page

Appendix B

Bibliography

1. 
   Novatsky A.A Electronic notes for the course “Computer Electronics”.
2. 
   J. F. Young Robotics Leningrad, “Mechanical Engineering”, 1979
3. 
   A. A. Krasnoproshina Electronics and microcircuitry Kyiv, “Higher School”, 1989.
4. 
   Denisenko T.A., Tikhonchuk S.T. Guidelines for the use of controllers of the SIMATIC S5 family, OGPU, 1998.
5. 
   Yampolsky L.S., Melnichuk P.P., Samotkin B.B. Flexible computerized systems, Zhitomir, 2005
6. 
   D. Morman, L. Heller Physiology of the cardiovascular system.
7. 
   Mandel W.J. Cardiac arrhythmias. Mechanisms, diagnosis, treatment. In 3 volumes
8. 
   Yakovlev V.B., Makarenko A.S., Kapitonov K.I. Diagnosis and treatment of heart rhythm disorders.

Heart disease is one of the three most common illnesses in the world. Abnormal blood pressure is a sure sign of developing problems with a major vital organ.

The first-class tool for detecting and preventing heart disease is a blood pressure monitor. Each medical device has its own “biography” and features. Next we will look at device and principle of operation of the tonometer, as well as their types and features of choice.

Tonometer: a look into history and demand

The first prototype appeared in France in 1828. Doctor Jean Louis Poiseuille used a special pressure gauge to measure the pressure.

The device was based on mercury. It was inserted into the artery through a cannula, which made it possible to determine blood pressure in real conditions.

The non-invasive (without direct penetration into tissue) method was published only after almost 30 years. The German physician Karl von Vierordt invented a special device, later called a sphygmograph, in 1854. The technology has rapidly gained popularity and authority in the medical community.

Initially, blood pressure was measured in animals. People were remembered only in 1856, when the famous surgeon Favre connected a device to a human artery during an operation.

The world-famous classic tonometer appeared in 1905 after the report of Nikolai Korotkov, the great Russian surgeon.

In 1965, doctor Seymour London improved Korotkov’s invention and released an automatic version, which entered medical use in parallel with the traditional model.

Currently, the demand for the device is difficult to overestimate. Statistics eloquently demonstrate: more than half of the world's population has high blood pressure. Cardiovascular diseases have become a real scourge of our time. They are “getting younger”: young people are increasingly suffering from heart disease. The CIS countries were not spared the misfortune either. Hence the need for timely detection of diseases. The device is traditionally included in the arsenal of essentials for elderly people and people suffering from heart disease.

Design and principle of operation of the tonometer

All meters can be divided into two large classes:

• Mechanical. Traditional models. They consist of a cuff (special strap), an air pump (the so-called bulb), a stethoscope and a pressure gauge.
• Automatic. Produced on the basis modern technologies. Consist of electronic filling and cuff.

There are so-called semi-automatic blood pressure monitors. They have no independent meaning, since they represent a unique combination of existing classes.

Mechanical varieties are still in use today.

The enormous popularity arose due to the simple and unpretentious design of the device. Features of mechanical tonometers:

• Large range of cuffs. There are “sleeves” for both older people and children.
• The supercharger (pear) has two valves: return and relief. The former holds the air in the cuff, the latter releases it.
• A stethoscope is a rubber tube designed to listen to heart sounds.
• The pressure gauge displays the data on the display. The moving arrow indicates the existing blood pressure.

The principle of operation of a mechanical tonometer: the “sleeve” compresses air, which is gradually pumped into the bulb. At this time, heart rhythms are listened to using a stethoscope. The result will be displayed on the device screen.

The traditional area for measurement is the shoulder. No one forbids determining pressure in other places, but it is on the shoulder that accurate and stable data is recorded.

An automatic tonometer is a more technologically advanced option for measuring blood pressure. Device Features:

• Lack of air blower (pear). Only the cuff and electronic unit are present.
• The equipment can store information about previous measurements.
• One button on the pressure gauge starts the entire process.
• Availability additional features. Automatic meters can measure body position indicator, arrhythmias and other indicators.

Pressure is measured using the oscillometric method. Operating principle: air is gradually pumped into the cuff and released by a special compressor.

The device monitors air fluctuations in the cuff that occur due to blood flow in the compressed area. The oscillations are converted into signals, which are converted into digital values ​​on the display.

Selecting a tonometer - mechanical or automatic

Advantages of mechanical meters:

• Accuracy. The devices determine blood pressure with a high degree of reliability. “Mechanics” can often be found in medical institutions.
• Unpretentiousness. There is no need to recharge or change batteries. There may be problems with the bulb, but the element can be easily replaced with another.
• Familiarity. Classic models are known to almost everyone.
• Cheapness. The purchase does not require large investments.

One of the disadvantages is the difficulty of measurement. It is sometimes difficult for older people to understand the operating principle of the device, and the readings of the moving needle are often simply unreadable for people with poor eyesight. It also requires some effort to measure: the bulb must be squeezed to pump air into the cuff.

Advantages of automatic models:

• Ease of use. All the person has to do is put on the cuff and press the button. The device will take the measurement itself.
• Intuitive interface. Manufacturers work to please consumers.
• Diversity. The market is replete with dozens of models with any configuration.
• Digital display. The indicators are displayed clearly and clearly. There are no arrows. Automatic apparatus Ideal for people with poor eyesight.

Disadvantages: the need for recharging and high cost. The electronic unit will have to be recharged over time. There is one interesting paradox associated with the high price: immodest price tags should repel the target audience, represented by older people.

In fact, the opposite pattern exists: automatic models are being purchased because of their ease and clarity of use. Mechanical varieties are used mainly by doctors.

There is no better option. A person gives preference to what is familiar. There is a wide range of medical devices on the market with different settings and functions. You can easily select the right device.

A tonometer is a device that has been in the service of humanity for several hundred years. Times change, but heart disease remains the same. Detection and prevention of possible heart-related diseases is the primary task of such an effective device as a tonometer.