Design of tester for blood pressure meters

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Dr. Benesóczky Zoltán
Department of Measurement and Information Systems

To test a blood pressure monitor device the air pulsing (pressure changing) in the inflated cuff is need to be simulated to sense the adjusted systolic and diastolic value by the monitor.

The pressure difference in the cuff is need to be generated indirectly. A solution to achieve this was born in project laboratory eariler. The key feature is a baby cuff fixed close to a speaker membrane. Controlling the speaker with PWM signal push the membrane to the cuff simulating the blood pulsing. We are going to use and develop this solution. It is important that the tester should work under different circumstances.

After the system design I created a microcontroller based solution which uses a simple equation for the modulation. I experienced that after tweaking some parameters the simulation result was reasonable (+/- 5 mmHg). This leads to a blood pressure device dependent tester hardware. To simulate the blood pressure parameters I created a teachable modell, which first I used to get the oscillometric spike amplitude. The goal was to create a system which can be easily extend to achieve other parameters. A feed forward neural network learns which cuff pressure belongs to which pressure difference. The basis of the hardware is a Xilinx evaluation board and I designed a spedific circuit for it. I realized the neural network and the microcontroller inside the FPGA. I designed a C# software using .NET framework for recording and purpose. The digital signal processing and teaching the network were implemented using MATLAB. After the network parameters are ready the network in the FGPA should be programmed with these values. After this the system is ready for the simulation.

The first version of the system and the monitoring software were designed during the project laboratory. In the first semester of the diploma the evaluation MATLAB sotware and the FGPA implementation were done. The system integration, documentaion and evaluation were done in the last semester.


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