Microchip Technology ARD00342 User Manual
MCP3901 and PIC18F65J90 Energy Meter Reference Design
DS51968A-page 26
© 2012 Microchip Technology Inc.
3.27
OFFSET_I_RMS
Square of the offset for RMS current reading, signed 16-bit value. Note that this value
should be similar to the ADC’s noise squared. At a gain of 1, the noise will be about
1 LSB, 2 LSBs at a gain of 2, 6 LSBs at a gain of 8, 11 LSBs at a gain of 16, and
22 LSBs at a gain of 32. There may be other sources of noise. Using the square of the
offset allows for higher accuracy. The value will be added before the square root is
taken when calculating the final RMS value.
should be similar to the ADC’s noise squared. At a gain of 1, the noise will be about
1 LSB, 2 LSBs at a gain of 2, 6 LSBs at a gain of 8, 11 LSBs at a gain of 16, and
22 LSBs at a gain of 32. There may be other sources of noise. Using the square of the
offset allows for higher accuracy. The value will be added before the square root is
taken when calculating the final RMS value.
3.28
OFFSET_V_RMS
Square of offset for RMS voltage reading, signed 8-bit value. Note that this value
should be similar to the ADC’s noise squared. For the voltage channel, the noise will
be about 1 LSB. There may be other sources of noise. Using the square of the offset
allows for higher accuracy. The value will be added before the square root is taken
when calculating the final RMS value.
should be similar to the ADC’s noise squared. For the voltage channel, the noise will
be about 1 LSB. There may be other sources of noise. Using the square of the offset
allows for higher accuracy. The value will be added before the square root is taken
when calculating the final RMS value.
3.29
GAIN_I_RMS
Current gain to produce X A/LSB. The value is always less than one (for example,
32,767 = 0.9999695).
32,767 = 0.9999695).
3.30
GAIN_V_RMS
Voltage gain to produce 0.1 V/LSB in the V_RMS register. The value is always less than
one (for example, 32,767 = 0.9999695).
one (for example, 32,767 = 0.9999695).
3.31
OFFSET_POWER_ACT
Active power offset (this is a straight offset, not the square, as with voltage and current).
A much larger value is needed because the power is a running sum. This is a 32-bit
signed value.
A much larger value is needed because the power is a running sum. This is a 32-bit
signed value.
Name
Bits
Cof
OFFSET_I_RMS
16
R/W
Name
Bits
Cof
OFFSET_V_RMS
16
R/W
Name
Bits
Cof
GAIN_I_RMS
16
R/W
Name
Bits
Cof
GAIN_V_RMS
16
R/W
Name
Bits
Cof
OFFSET_POWER_ACT
32
R/W