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Modbus Energy Measurements Ten Times Too High


Symptom: Reported energy readings are exactly ten times too high for the following integer registers:

  • EnergySum and EnergySumNR
  • EnergyA, EnergyB, and EnergyC
  • EnergyPosSum and EnergyPosSumNR
  • EnergyPosA, EnergyPosB, and EnergyPosC
  • EnergyNegSum and EnergyNegSumNR
  • EnergyNegA, EnergyNegB, and EnergyNegC
  • EnergyReacSum
  • EnergyReacA, EnergyReacB, and EnergyReacC
  • EnergyAppSum
  • EnergyAppA, EnergyAppB, and EnergyAppC

Cause: The WattNode® Modbus meter provides energy registers (including reactive and apparent energy) as either 32 bit integers or 32 bit floating point numbers. The integer energy registers are in units of tenths of a kilowatt-hour (0.1 kWh), which must be scaled. The floating point energy registers are in units of kilowatt-hour and should not need scaling.

Fix: Divide the reported measurements by 10.

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