Non liearity of sensors

[patricktran]

Hi there,
Can someone please help me to know more about a sensor's non linearity. I dont know a specific sensor, but I think there must be some sensors that are not linear, even within their specification range!!!!
Also, could you please tell me what techniques of dealing with non linearity?
Thanks alot
Patrick

 

[Oznog]

Well, there's ones billed as basically linear but with some known deviation that may be desirable to map out for precision apps. Then there's truly nonlinear ones like a thermistor or photocell.

If it's something that follows a formula, you might try to do the math, usually it's too complex to do easily. So typically we just use a lookup table. Now if you've got a 10 bit ADC you don't want to make a lookup table with 1024 values. What you do there is make a lookup table for regularly spaced adc values, like adc=0, 63, 127... Then do a linear approx for whatever inbetween value comes up. For adc=32, you take the average of the first and second table entry.