Adjusting range of FSR signal

Hello everyone,

I am trying to use force sensing resistors (FSR) to measure force for walking analysis. Through use of an op amp I can get the sensors to give an output from 0-250 pounds. However this only gives me a resolution of 0.25 lb. I only need to measure values around the 200 lb mark. Is there a way I can adjust the code to make the readings only occur at a higher weight range? I have already thought about using an If/Else loop but I'm afraid that I will loose the full range of the 10-bit value. Has anyone tried something similar to this?

Thanks for your time,

Taylor

The ADC has only 1024 steps.

It would be better to change your op amp circuit, so that the force range of interest spans 0 to 5 V.

I actually have my op-amp circuit set up to range from -5V to 5V. I can get values from my sensors at my target range (250-300 lb). The problem that I'm having is my resolution for the 0-250 lb range is 0.25lb and I want better resolution than that. Is there anyway I can analyze 200-300 lb instead, giving my a 0.1lb resolution?

Thanks for the reply

To get 0.1 pound resolution in the force range 200 - 300 pounds requires 1000 steps on the ADC. There are only 1024 steps.

There are several options. All require that you change your external circuitry.

The two simplest ones are:

1) Use the 5 V ADC reference and convert the force range 200-300 pounds to a voltage between 0 and 5 volts.

2) Use the 1.1 V ADC reference and convert the force range 200-300 pounds to a voltage between 0 and 1.1 volts.

Or, buy an external ADC module with higher resolution. Adafruit sells one.