Sensirion's miniaturized differential pressure sensor SDP3x is a semiconductor MEMS version of the traditional hot wire anemometer. It is easily attached to a not inflated mat in order to accurately measure body movements below the mattress. This includes obviously big movements (e.g. lying down/getting up), but also smaller movements like respiration and even every heartbeat. The mat consists of two ABS sheets (1mm) taped together and the volume in between is filled with volume cloth. (Figure 1).

As opposed to diaphragm based differential pressure sensors, Sensirion's CMOSens^® differential pressure sensor characteristic shows high sensitivity especially at low differential pressures (Figure 2). This allows to reliably measure ultra-low differential pressures and therewith accurately measure the flow moving in and out of the mat triggered by body movements.

The measurement of the differential pressure and derived heart rate is presented in Figure 3.

To build a sleep quality monitor the Sensirion differential pressure sensor SDP3x series (Figure 4) can be sourced from distributors listed on the Sensirion website. Communicate with the digital sensor over I²C according to the explanations in the SDP3x series datasheet or use the appropriate evaluation kit.