I got one of these FSR sensors and applied a static load to them. The setup was as follows: a piece of rubber, an eraser actually, and than I leaned a brick on the top of it. Than I just read the resistance with multimeter.
At first it was showing around 100.0 kOhm, but that reading was constantly falling, albeit at a very slow rate. After about 5 minutes, it reached 60 kOhm, and after another 5 minutes it was around 35 to 40 kOhms. It actually continued falling, but I gave up watching it. I would say this is pretty useless for any type of the pressure measurement.
Is it possible that something is wrong with the sensor I got? Or, do these sensors need to be used in a different way to get a more constant measurement?
I got one of these FSR sensors
Link? They are not all the same.
I would say this is pretty useless for any type of the pressure measurement.
Yes I would agree with you on that one.
Is it possible that something is wrong with the sensor I got?
Don't know, no link to what you actually got.
I am not sure that they are designed to be used in this way.
Here is the link:
FSR
So what you are saying, they are useless for static loads? Is there anything else that is better suited for static loads?
Well that web page says it all:-
Best used when relative pressure sensing is required (not very accurate or repeatable)... but fun.
Is there anything else that is better suited for static loads?
There are many types of load cell, but all suffer from drift under constant load. This is because of the nature of resistant materials. Even springs can become distended, that is why there is a zero calibration method on most weighting systems.
Yeah, thanks.
I didn't understand what they meant by 'relative' pressure. They should have called it 'short' or 'impact' or 'quick'. 'Relative' is quite meaningless.
I didn't understand what they meant by 'relative' pressure.
The reading between one pressure and another.
Yeah, what do you think, will the strain gauges do the job with static loads? Like these: http://uk.rs-online.com/web/c/?searchTerm=strain+gauge&sra=oss
They depend on substrate, which is usually aluminum bar. Aluminum bar would stay elastic, so no creep.
All mechanical strain gauges will suffer from creep on a static load, no matter what they are made of. You just have to get one that is small, or insignificant compared to your requirements, which you haven't mentioned yet.
Raw stain gauges are harder to interface and normally requires some sort of amplification and temperature compensation.
I guess the maximum force I would be like to measure would be around 30 N.