FSR value drifting with static load

Hey guys,

I’ve hooked up a FSR following the tutorial from bildr Force Sensitive Resistor + Arduino - bildr but I have an issue where the value slowly climbs by a couple of points every couple of minutes when the force is static. The sensor is under a rubber mat which has a coffee pot resting on top. At first I thought it was possibly related to temperature but the value never stabilized and continued to climb. If I take the load off, and then put it back on it will “reset” but then start climbing again. Is this just the nature of the sensor or is there possibly something else going on? Another thing to note is I swapped out the resistor for a 1K instead of a 10K so it takes more force to register readings.

Yes, they drift. The temperature may be affecting it too - these are not precision devices and cannot be accurately callibrated. For precise force measurement a load-cell is usually employed.

The sensitive part of the FS resistor is conducting particles in a rubbery insulating substrate. Under pressure the particles are forced very very slightly closer together and quantum-tunneling of electrons between particles increases. This tunnelling is acutely sensitive to distance. The rubbery substrate will continue to deform slowly under load for ages, its the nature of soft elastic materials.