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Why the values of calibration registers makes more gap between measured value and ADC?

Question asked by ghsung on Nov 30, 2017
Latest reply on Dec 4, 2017 by Gary.Kang.AnalogDevices

Hi,

I'm a user of ADE9000 evaluation board.

 

I compared measured values of current, voltage, power with clamp-meter(multi-meter) to measured values of ADC in ade90xx evaluation software program, and it's very small error between them.

For example, the measured values of current with clamp-meter was 0.23A and the converted value from ADC(AIRMS) was 0.229A.

ADE9000 datasheet recommends to use calibration registers so I downloaded ADE9000-Calibration-Tool on the analog devices site.

At first time, I thought calibration makes more smaller gap between measured values with clamp-meter and ADC.

However, after I applied AIGAIN and AVGAIN to ade90xx evaluation software as calculated in calibration tool (excel file), the AIRMS and AVRMS value was more bigger gap to measured value of clamp-meter.

After calibration, AIRMS value was 0.27A.

 

I realized that the xIGAIN and xVGAIN registers are affected by nominal current and voltage. It means calibration makes much closer to nominal value regardless of real current and voltage.

Why and when should I perform calibration if it makes bigger gap between ADC and real values?

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