Hi Folks The range node is linear, does a non-linear conversion node exist?

Thanks, I have some 100K pot on order.

Hi Colin Install a 100K trimmer pot today and still see non-linear behavior. Source Voltage - Dashboard reading (through PI-Plate) 09.4 - 09.4 (calibrate here – measured voltage adjusted to equal displayed voltage) 18.7 - 18.9 28.2 - 24.6 Seems like creating equation in a node may be a solutio…

Not sure what your 9v source is. But if it’s one of those small batteries they have a significant internal resistance that can affect measurement.

Thanks for your assistance. I am measuring the voltage directly at the battery terminals and connect them in series to achieve 3 voltage points for testing. Don't have a bench power supply. I read the voltage from the DAQCplate Pi-Plate. At 9.4 volts (measured at the battery) the voltage divider is …

Rather that working around whatever the problem is you should identify why your measurement is not linear. What does 0 volts give?

Also which pi plate are you using? Finally, what do you see if you put the voltmeter on the input to the pi plate? [Edit] I see you have said it is a DAQCplate. The spec seems to say those are 0-4 volts, so you shouldn't go more than that, which will explain part of the non-linearity, so fix tha…

[image] HS10: 09.4 - 09.4 (calibrate here – measured voltage adjusted to equal displayed voltage) 18.7 - 18.9 28.2 - 24.6 Seems like creating equation in a node may be a solution. Use the three data points create a processing equation. If you must go down this avenue, read up on "curve fit…

The problem with that is that if the problem is that the input impedance of the ADC is not large compared to the pot then that impedance may well vary with temperature, so @HS10 could configure the curve to compensate, but the calibration would drift with temperature. Also he would most likely need…

[image] Colin: The correct solution is to understand and fix whatever is making it non-linear. 100% agree Colin. Precisely why I prefaced it with "If you must go down this avenue"

[image] Colin: the calibration would drift with temperature And the voltage also change with temperature changes

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Range node - non linear

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Sean-McG 31 January 2022 16:19 31

That looks like a bit of a beast

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Range node - non linear

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