Hello all,

Maybe someone more experienced in electronics can help me with (I suppose) a newbie problem...

I'm including a FSR pressure sensor in a circuit as a variable resistor.
The problem is that FSR resistance doesn't go below approx. 5K at the maximum pressure that will be applied (it's inverse logarithmic?).
Ideally, I need the resistance to gradually go to zero, but maintaining the characteristic of the sensor. So in a force-resistance graph, the graph is shifted to down, if that makes sense.

Can anyone suggest a circuit I can use?
Thanks a lot in advance.

 

Going over the FSR material (the PDF file that loads off the home page), that's as good as it gets. I would direct you attention to the statements on page 8. It is not meant to be a precision device.

Ordinarily, it could go into a resistive divider, and have an op amp with an offset voltage applied make the sensor signal go to zero. But the notice of variance of up to +/- 25% makes that a bit iffy.

Do some experimenting. See how reproducible the output is over many trials. If it's closer to the best-case +/- 5%, then the op amp and offset voltage may get you there.

 

Hi Beenthere,

thanks for the help.
The sensor doesn't have to be very precise, it's used as a control.
But it does have to go down to (almost) 0 resistance.

I was thinking of using an opamp, but don't know how to go about it exactly.
Any advice on components/circuit?

Thanks again, really much appreciated.

 

Take a look at this page:
http://www.imagesco.com/sensors/opamp.html
You could adapt that circuit to get the output you need - but it will be in DC voltage, not resistance.