Hello everyone! I continue to summarize and post in a condensed form my experience in electronics repair. I present my Top 10 most common malfunctions of tonometers, which was born as a result of accidental repairs of medical equipment and communication with other Masters. I won’t say that I’m a great specialist in this area, but I came across some things and successfully fixed them. Let's start the rating. The locations of malfunctions of tonometers and blood pressure meters are sorted by the frequency of occurrence of the malfunction.
What to do if it measures incorrectly
First, you need to make sure that the blood pressure measurement procedure itself is carried out correctly. Many people use wrist blood pressure monitors, which is not recommended for people over 45 years of age. In addition, the error of such devices can be up to 20 mmHg. Art.
The readings of everyone else can also be influenced by the psychological state at the time of measurement or by incorrect posture.
Having eliminated all factors, all that remains is to take the device to an accredited organization that has a license to service medical devices, where specialists will be able to identify and eliminate the error.
DIY tonometer repair: step-by-step master class
Now digital automatic and semi-automatic blood pressure monitors have become very popular. They are much easier to use than mechanical ones and have fairly accurate indicators.
As for automatic tonometers, they are the easiest to use. For them to work, just put the cuff on your arm and press the corresponding button. The device itself will do the rest.
The semi-automatic device works on the same principle, the only way it differs from the first one is that the air is not pumped by a compressor, but by a rubber bulb manually.
Although automatic appliances seem more attractive, they have their drawbacks. One of them is the mandatory use of high-quality batteries with a large capacity. These batteries are more expensive than regular batteries, but their use is necessary since the air compressor requires sufficient power to operate.
To operate a semi-automatic device, it is enough to have mid-segment batteries, which last for 2-3 years of use. Another advantage of these devices is that replacing the rubber bulb does not require much money or effort. Repairing a compressor can cost a pretty penny, which does not always justify the cost. Sometimes, in such cases, it is better to buy a new device.
A semi-automatic blood pressure monitor can serve faithfully for several years, but over time, it can also develop various problems.
This is due to the wear and tear of some elements, especially those that are most often used. It is clear that there is no point in repairing a rubber bulb or hose. This also applies to the measuring cuff.
Due to their low cost and distribution, they can be purchased at one of the medical equipment stores.
As for electronics, there are ways to independently repair failed elements and circuit components.
In the photo there is 1 microlife tonometer, which has a problem with turning on. To be more precise, to start it, you need to press the “ON” button several times while making circular movements with your finger.
Rice. 1. A tonometer that has a problem turning on
Although the device is more than three years old, it works great. The only drawback is this button, which at the most inopportune moment does not want to perform its function. This can be annoying for someone who is already feeling unwell.
This problem can be easily fixed. It is enough to simply replace the button or solder its contacts. Before drawing a conclusion about a malfunction of the tonometer, its operation should be checked by installing new batteries. Only if after this nothing has changed, then you can think about repairs.
So, you should start by disassembling the case.
Rice. 2. Disassemble the case
To do this, open the battery compartment (Figure 2) and take out all the batteries from there. In this compartment you need to look for the screw securing the two halves of the case. In this tonometer it is hidden under the warranty seal (Figure 3).
Rice. 3. Find the fastening screw
We open the seal and unscrew the screw.
Rice. 4. Unscrew the screw
There is only one in this device, but there are times when there are several of them.
If one of them remains unscrewed, then during disassembly the entire case can be broken. After making sure that all the screws have been removed, we try to separate the two halves of the case using a screwdriver or a knife blade (Figure 5).
Rice. 5. Separate the 2 halves of the body
This should be done carefully, helping with your fingers. After removing the case cover, carefully remove the board and turn it over.
Rice. 6. Remove the board
So that nothing interferes, remove the tube tee from the groove in the housing (Figure 7 and 8).
Rice. 7. Take out the tube teeFig. 8
Now you have access to the soldering points of the problem button pins.
Rice. 9. Tonometer printed circuit board
If you look at the printed circuit board, the two arms of the button are parallel to improve contact. When connected to the terminals of a multimeter button in resistance measurement mode and the button turned on (Figures 10 and 11), the device showed an open circuit, although it should be the other way around. Only when pressing with probes on the solder joints did a chain occasionally appear.
Rice. 10. Check with a multimeterFig. eleven
This indicated a soldering defect, as a result of which the contact did not operate accurately.
Sometimes, over time, a microcrack forms around the output of the part, which may not be visible to the naked eye.
This is especially true for electronic components that are heated or subject to mechanical stress. For example, the same button mentioned above.
If the button turns out to be inoperative, it can be replaced with a similar one from the old technology. For example, from the front panel of a satellite TV tuner or other non-working equipment (Figure 12).
Rice. 12. Example of where to get the button
Also, such buttons are sold on the radio market or online store of electronic components. In this case, the problem was precisely in the folder, and there was no particular need to change the button.
You can solder the pins of the button with a soldering iron with a power of 25 W. A soldering iron with more power can overheat the traces and cause them to peel off. Also, they are not very comfortable to work with because of the thick tip.
To achieve good soldering results, it is necessary to use high-quality flux. The simplest is rosin dissolved in alcohol. You can use regular rosin.
So, we cover the soldering points with flux (Figure 13) and after heating the tool, we solder the connection points of the button pins (Figure 14).
Rice. 13. Cover with flux Fig. 14. Use a soldering iron
There is no need for tin, since what is on the board will be enough.
After soldering is completed, we wipe these places with cotton wool soaked in alcohol or cologne. This will remove debris and excess flux. Next, we connect the multimeter probes to these terminals, and by pressing the button we look at the result.
Rice. 15. Result of soldering
The board should “sit” on the guide plastic pins (Figure 16).
Rice. 16. Reinstall the tonometer board
Next, the tube holder must be installed in the appropriate groove. We cover the board with the top cover and forcefully snap the case into place.
Rice. 17. Install the tube holder into the groove
Tighten the screw in the battery compartment.
Rice. 18. Tighten the screw
We install the batteries and try to turn on the device.
Rice. 19. The tonometer is working! The renovation is complete.
The tonometer turns on the first time, which means that the problem with the button is solved.
Source: https://www.asutpp.ru/remont-tonometra-svoimi-rukami.html
In what cases is repair of medical tonometers required?
Among the most common breakdowns of tonometers:
- The pressure gauge needle falls out (typical of mechanical tonometers).
- Loss of tightness resulting in air leakage. As a rule, damage occurs at the hose connection areas, in the bulb, and also in the cuff.
- Air bleed valve stuck. In most cases, such a malfunction requires replacement of the tonometer bulb.
- Bleeding air too quickly. In such a situation, it may be necessary to replace the air bleed valve or the entire blower.
- Displaying incorrect indicators on the digital screen of the device. If such a malfunction occurs, you should try replacing the batteries. If this does not help, the cause is most likely an air leak in the cuff, tube or bulb.
It should be remembered that blood pressure monitors are professional medical equipment, the repair of which should be carried out by experienced specialists of appropriate qualifications.
Initial setup
The best way is to buy a blood pressure monitor at a pharmacy or specialty store. There they are already checked and adjusted using a standard. This applies to mechanical models. Electronic ones, which are now the most popular, are tested by the manufacturer at the factory.
You can find out that the device has passed the accuracy test using the example of manual tonometers from Omron (leaders in sales on the Russian market). Each copy has a special sticker-seal, which confirms that no one used it after the repair by the master.
The only thing is that after the purchase the user needs to set the date and time. You can do this yourself:
- Remove the battery pack and insert it back.
- Turn on the device.
- After this, setting the date and time is activated.
- Using the “+” and “-” buttons, first the date is set, then the month. After adjusting each number, you need to press the “Start/Stop” button.
- After setting the date and pressing “Start/Stop”, the time indicator will appear. Indicators are set in the same way.
Important! When purchasing mechanical models, you need to pay attention to the dial. The pressure gauge needle should show exactly 0.
