How is an Offset/No Load Calibration performed on MCP39F501?

Refer to the MCP39F501 datasheet. The 'Offset/No-load-calibration' described in Section 9.6 is used to remove light load or residual power/current. You need to calculate for the correct value of offset that will make the current equal to zero. The gain and the range need to be taken into account. The block diagram to determine the voltage, current, and power can be found in Figures 5-2, 5.3, and 5-3 of the datasheet.

For example, you want to calibrate the current: the RMS current can be computed by the equation based on Figure 5-2. CurrentRMS = Sqrt( i +/- OffsetCurrentRMS ) * GainCurrentRMS / 2^Range. At no load, 'i' should be zero. Likewise, CurrentRMS should be zero. If you read a residual RMS current of 0.08 A, you need to solve for OffsetCurrentRMS value, given the value of gain and the range, to compensate for this residual current. Take note of the difference in the block diagram of the current and voltage.

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