EMC Consutancy & Design solutions
Blood Pressure emulator
The medical market has the highest number of regulations and standards. This is because it is the most regulated market. It is for a valid reason that it has so many regulations and standards. It is imperative to make sure that the equipment used by doctors and nurses does what it is supposed to do according to the manufacturer.
Can you imagine a scenario where a mobile phone could interact in some way with some of the equipment used in a hospital? Can you imagine what might happen if a surge caused by a thunderstorm damage an ECG machine? There is no way this could ever happen. This is one of the reasons why some of the EMC tests for a medical device can be so challenging and challenging to pass. There is no doubt that designing electronics for the medical industry is not an easy job for everyone to do. You need to have an engineer who has vast experience and knows what he is doing so that you will get the most effective results. The consequences of not doing so will result in quite a bit of trouble for you.
Passing at the first attempt!
The challenge
In some cases, it may be necessary to monitor the blood pressure of the patient from more than one monitor at the same time. As an example, you might have a monitor pointing at a doctor, and another pointing at an anesthesiologist.
In cases like this, you run into a problem in that you don't really want to add another blood sensor to the patient. So the most effective thing to do is to be able to simulate patients' blood by electronic means.
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While our customer has software expertise in-house, they do not have electronic and EMC expertise in-house, and this is why we have been hired not only as an EMC consultant but also as a design provider.
Keeping technical details out of the way, you should know that this kind of design is very difficult from a technical standpoint. This is because you have to make blood measurements first. Then you need to convert the analogue signal to a digital signal. Finally, you need to convert the digital signal back to the analogue signal. It is essential that all those operations are carried out in real-time. The secondary monitor cannot display the blood pressure of, let's say, one or two seconds ago.
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As part of this particular design, we were asked to design the electronics to perform the digital-to-analogue conversion. Despite a few minor issues, we were able to pass EMC without a hitch. We actually passed EMC on our first attempt. This is something we are very proud of, so we decided to add one of the case studies.
The EMC challenge
There are a lot of challenges that can be encountered when it comes to passing radiated emission on differential signals with voltage resolutions of a few microvolts. It was the radiated emission that we were most concerned about since it was the most likely to fail.
We have developed software that can emulate waveforms such as "patient waveforms", sine waves, triangle waves, and constant blood pressure waveforms. Following that, we saved those waveforms in a log file and asked our customer to do some sort of post-test verifications based on the data that was received from the software, based on the data that had been received. The solution we came up with worked on the first try.