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View Full Version : [Question(s)] Force Sensor equation from analog to lbs or force

BrandonG32
04-29-2008, 09:52 AM
Hi,
I was wondering if there was an equation for the Force Sensor .2'' and .5'' that will allow me to get a meaningful value. I have the analog values that are coming out but I want to relate that to some type of force. Has there been equation already made out for these sensors? If so, can someone please push me in that direction. Thanks.

archcvd
04-29-2008, 01:10 PM
If you take a look at the datasheet, there's a curve that correlates the resistance with force applied (well the weight of a mass in grams actually).

http://www.trossenrobotics.com/images/productdownloads/FSR%20data.pdf

You could take those points and have a calculator find an equation for you that would best fit the data then use the equation in your program. Since this equation takes resistance as a variable make sure you find out what resistance corresponds to what analog value so you know how to convert.

Makes sense, right?

Adrenalynn
04-29-2008, 01:39 PM
It may be a tad more complex. At a glance, the force v resistance graph is a power-law graph. So it's going to depend how accurate we need the fit to be. Ideally we'd turn to linear algebra here, and start looking to do regression analysis on the empiracle data. If we need to get a high level of precision, we'd probably start looking for work done that appears to fit our power law curve.

I could feed it to MatLab later and see if it turns out a good fit quickly or if you'd just have to do regression to approximate every time.

Another point to consider with force sensors is that you really need to do your own force testing in-situ, as the way you mount it, what it's mounted to, and what is surrounding it will greatly change your readings. Resistance isn't just electronic/electromechanical in this case, it's also purely mechanical.