Analog, compact and economical solution for the compensation of implantable piezoresistive blood pressure sensors for wireless medical monitoring

Abstract

This article presents an analog method of compensation for thermal drifts of implantable piezoresistive blood pressure sensors used in wireless medical monitoring. A PNP transistor-based circuit in parallel with a variable resistor is used. This circuit is in series with the pressure probe constituted of four piezoresistors in Wheatstone bridge. This analog method is effective in reducing the thermal drift of the sensor and also has a low cost and consumption. The thermal drift of the sensor before compensation is 9.55 mmHg over the temperature range [34°C - 39°C] with the pressure of 300 mmHg and after compensation, the drift is reduced to 2.5 mmHg. This method has been validated with 3 pressure levels (0, 100, 200 and 300 mmHg).