Oscilloscope integration error 2

[htsao]

Hi,

Can anyone explain why my oscilloscope seems to have an error while performing an intergration function? Even when the probe is shorted to itself, there is a ~1.0 mVs/s positive slope to the integration calculation (see attached picture).

I am measuring the total energy used by an electric motor and its supporting circuitry. I connected a 0.1 ohm resistor in series with a battery terminal and hooked up a probe from an Agilent 54266D oscilloscope to either end of the resistor. This way, the voltage output on the scope can directly translate to the current going through the resistor.

I am using the scope's integration function to calculate the total energy used during an actuation and I want to eliminate the effect that this 1.0 mVs/s error has on my results.

Thank you for your help.

 

[Skogsgurra]

All integrators, analogue or digital, have that problem. In your case, the AD:s offset seems to be the problem. Do an offset compensation, either directly on the input amplifier or in the integrator. Some integrators have a "leakage" function that keeps the integrator drift low. But that, of course, affects long term accuracy. Integrators are not easy to use.

Gunnar Englund

http://www.gke.org

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