FSR voltage steadily increasing

I have set up an FSR using the circuit defined here: Using an FSR | Force Sensitive Resistor (FSR) | Adafruit Learning System. The fsr does appear to work as expected in that as I add pressure, then vintage across the pull down resistor increases.

However I have been trying to calibrate the sensor by placing various weights in the sensor and recording voltage. What I have noticed is that if I put a fixed weight directly in the center, the voltage will continuously increase. I have seen this using various FSR sensors.

Is this something that has been observed by others and is expected or are there ways to ensure a more stable voltage readout.

Hi, @cchrysos
Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".

If you need to measure a mass, you would be better to use a load cell.
From what I can see FSR's are good for sensing a change in pressure, but not as a calibrated measuring device.

Tom... :smiley: :+1: :coffee: :australia:

My ultimate goal isn't to measure mass, I was just using fixed mass objects to try and figure out the relationship between force to resistance in that sensor since the data sheet did not include it. So I would like to use the fsr for force/pressure but I want to optimize the circuit for my purpose which is why I'm trying to calibrate it. Have you noticed this effect before when using an fsr?

Can you post your circuit please and code please

I have used these sensors and did the same calibration using known weights. The response was nearly linear, except the first quarter of the graph was more exponential. But a linear interpretation wouldn't be far off.