71M6515H
Energy Meter IC
DATA SHEET
MARCH 2008
Example: For a Wh measurement, an error of +1% was observed at 1A. If VMAX is 600V and IMAX = 208A,
and if the measurement was taken at 240V, we determine QUANT_W as follows:
1
240⋅1
100
QUANT _W = −
= −18460
600⋅208⋅1.04173⋅10−9
The negative value obtained by the calculation will compensate for the positive error. It does not matter which current value
is chosen as long as the corresponding error value is significant (5% error at 0.2A used in the above equation will produce
the same result for QUANT_W).
Input noise and truncation can cause similar errors in the VAR calculation that can be eliminated using the QUANT_VAR
register.
VFEED_A (0x44), VFEED_B (0x45), VFEED_C (0x46)
These registers hold the compensation factors for feedthrough used for calibrating Rogowski coils. The allowed range is
(215-1) to -(215-1). See the section on Rogowski Coil Calibration for details.
Registers Controlling Basic Function and Settings of the 71M6515H
CONFIG (0x16)
The four bytes written to this register determine the basic operation of the 71M6515H. The function of the 28 bits used for
this register are explained below:
Bit 0: This bit (VAH_SELECT) determines the method used by the post-processor for determining the apparent energy
measured in VAh. If the bit is 0 (default), the calculation is based on VRMS, IRMS and the time (t) per the formula:
VAh = VRMS * IRMS * t
The accuracy of the result can be improved for low currents by setting Bit 0 to 1. The calculation is then based on the Wh
and VARh values per the formula:
VAh = Wh2 +VARh2
Using the calculation method above, high accuracy can be achieved for low currents.
Bit 3: This bit (RTM_EN) enables the Real-Time Monitor function when set to 1.When used, the RTM signal is available at
the TMUX pin.
Bit 4: This bit (CE_EN) enables the CE when set to 1. The CE has to be enabled for most metering functions.
Bits 7-5: These three bits (EQU) define the equation (see table below) to be implemented by the CE.
EQU
0
Watt & VAR Formula
VA IA
Application
1 element, 2W 1ø
1*
2
VA(IA-IB)/2
1 element, 3W 1ø
VA IA + VB IB
2 element, 3W 3 øDelta
2 element, 4W 3ø Delta
2 element, 4W 3ø Wye
3 element, 4W 3ø Wye
3*
4*
5
VA (IA - IB)/2 + VC IC
VA(IA-IB)/2 + VB(IC-IB)/2)
VA IA + VB IB + VC IC
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