71M6521DE/71M6521FE
Energy Meter IC
DATASHEET
JANUARY 2008
CE
Address
Name
Description
0x76
0x72
0x75
0x71
W0SUM_X
The sum of Watt samples from each wattmeter element (In_8 is the gain
configured by IA_SHUNT or IB_SHUNT).
LSB = 6.6952*10-13 VMAX IMAX / In_8 Wh.
W1SUM_X
VAR0SUM_X
VAR1SUM_X
The sum of VAR samples from each wattmeter element (In_8 is the gain
configured by IA_SHUNT or IB_SHUNT).
LSB = 6.6952*10-13 VMAX IMAX / In_8 Wh.
WxSUM_X is the Wh value accumulated for element ‘X’ in the last accumulation interval and can be computed based on the
specified LSB value.
For example with VMAX = 600V and IMAX = 208A, LSB (for WxSUM_X ) is 0.08356 µWh.
Instantaneous Energy Measurement Variables
The Frequency measurement is computed using the Frequency locked loop for the selected phase.
IxSQSUM_X and VxSQSUM are the squared current and voltage samples acquired during the last accumulation interval.
INSQSUM_X can be used for computing the neutral current.
CE
Address
Description
Name
FS
232
≈ 0.587 ⋅10−6 Hz
0x79
FREQ_X
Fundamental frequency. LSB ≡
0x77
I0SQSUM_X
The sum of squared current samples from each element.
LSB = 6.6952*10-13 IMAX2 / In_82 A2h
0x73
0x78
0x74
0x7D
0x7E
I1SQSUM_X
V0SQSUM_X
The sum of squared voltage samples from each element.
LSB= 6.6952*10-13 VMAX2 V2h
V1SQSUM_X
WSUM_ACCUM
VSUM_ACCUM
These are roll-over accumulators for WPULSE and VPULSE
respectively.
The RMS values can be computed by the MPU from the squared current and voltage samples as follows:
IxSQSUM ⋅ LSB ⋅3600⋅ FS
VxSQSUM ⋅ LSB ⋅3600⋅ FS
IxRMS
=
VxRMS
=
NACC
NACC
Other Measurement Parameters
MAINEDGE_X is useful for implementing a real-time clock based on the input AC signal. MAINEDGE_X is the number of half-
cycles accounted for in the last accumulated interval for the AC signal.
TEMP_RAW may be used by the MPU to monitor chip temperature or to implement temperature compensation.
v1.0
© 2005-2008 TERIDIAN Semiconductor Corporation
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