Datasheet

71M6521DE/DH/FE Data Sheet
Page: 86 of 107 Rev 3
Fundamental Energy Measurement Variables
The table below describes each transfer variable for fundamental energy measurement. All variables are signed 32
bit integers. Accumulated variables such as WSUM are internally scaled so they have at least 2x margin before
overflow when the integration time is 1 second. Additionally, the hardware will not permit output values to ‘fold back’
upon overflow.
CE
Address
Name Description
0x76
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.
0x72
W1SUM_X
0x75
VAR0SUM_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.
0x71
VAR1SUM_X
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
Name
Description
0x79
FREQ_X
Fundamental frequency. LSB
6
32
10587.0
2
−
⋅≈≡
S
F
Hz
0x77
I0SQSUM_X
The sum of squared current samples from each element.
LSB = 6.6952*10
-13
IMAX
2
/ In_8
2
A
2
h
0x73
I1SQSUM_X
0x78
V0SQSUM_X
The sum of squared voltage samples from each element.
LSB= 6.6952*10
-13
VMAX
2
V
2
h
0x74
V1SQSUM_X
0x7D
WSUM_ACCUM
These are roll-over accumulators for WPULSE and VPULSE
respectively.
0x7E
VSUM_ACCUM
The RMS values can be computed by the MPU from the squared current and voltage samples as follows:
ACC
S
RMS
N
FLSBIxSQSUM
Ix
⋅⋅⋅
=
3600
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.
ACC
S
RMS
N
FLSBVxSQSUM
Vx
⋅⋅⋅
=
3600