Help me identify a sensor I got from a PCB

Question

I am currently working on a blood pressure monitoring system(for a class) and I was handed an old, non working wrist blood pressure monitor to salvage any components I could. So I tore it down, took out the air valve and air pump. There was yet another component soldered to the PCB which had a hose inlet(which led to the cuff), so I figured it must be the pressure sensor. Indeed it was, see the attached images:

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I figured it is a pressure sensitive resistor since it has only two pins, however the multimeter gave a reading exceeding 2000kOhm. I tried blowing into the inlet to simulate pressure rise, yielding no change in resistance whatsoever. From one of the attached images we can see that the two pins of the sensor were connected via some capacitors to the microcontroller. If anyone got any info on the name of this sensor, or maybe a similar one, it'd be appreciated.

If the resistance seems non-reasonable then it could be a piezoelectric (strain-gauge) type device. Perhaps try to simulate pressure and measure DC volts on the u/m Ω scale. — Steve, May 31 '18 at 16:53
@Emir Keep taking it apart. Remove the screws, remove the metal plate. Post pictures of what's underneath the metal plate. (Forget about salvaging from consumer grade junk, though. It's only good for education purposes, but it doesn't work as a parts sourcing strategy. More of that rationale here.) — Nick Alexeev, Jun 01 '18 at 17:11

score 3 · Accepted Answer · answered May 31 '18 at 16:56

3

That is a capacitive/piezoelectric pressure sensor. The ones we use are in the 10 - 100 pF range for blood pressure.

answered May 31 '18 at 16:56

T2JSplode

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That could explain the 'infinite' resistance. – Emir Šemšić May 31 '18 at 17:03
Agreed. And not fun trying to find a replacement not knowing if its faulty. – T2JSplode May 31 '18 at 17:27

Help me identify a sensor I got from a PCB

1 Answers1