Datasheet

ADE7763 Data Sheet
Rev. C | Page 38 of 56
WRITE WGAIN VALUE TO THE WGAIN
REGISTER: ADDR. 0x12
CALCULATE CFDEN VALUE FOR DESIGN
WRITE CFDEN VALUE TO CFDEN REGISTER
ADDR. 0x15 = CFDEN
SET HALF LINE CYCLES FOR ACCUMULATION
IN LINECYC REGISTER ADDR. 0x1C
SET I
TEST
= I
b
, V
TEST
= V
NOM
, PF = 1
CALCULATE WGAIN. SEE EQUATION 43.
SET MODE FOR LINE CYCLE
ACCUMULATION ADDR. 0x09 = 0x0080
ENABLE LINE CYCLE ACCUMULATION
INTERRUPT ADDR. 0x0A = 0x04
READ LINE ACCUMULATION ENERGY
ADDR. 0x04
RESET THE INTERRUPT STATUS
READ REGISTER ADDR. 0x0C
INTERRUPT?
NO
NO
YES
YES
04481-A-086
RESET THE INTERRUPT STATUS
READ REGISTER ADDR. 0x0C
INTERRUPT?
Figure 72. Calibrating Watt Gain Using an Accurate Source
Equation 43 describes the relationship between the expected
LAENERGY value and the LAENERGY measured in the test
condition:
WGAIN = INT








×








−
12
)(
)(
21
nominalIB
expectedIB
LAENERGY
LAENERGY
(43)
The nominal LAENERGY reading, LAENERGY
IB(nominal)
, is the
LAENERGY reading with the test current applied. The expected
LAENERGY reading is calculated from the following equation:
LAENERGY
IB(expected)
=
INT














×
+
+
×
WDIV
CFDEN
CFNUM
Timeon
AccumulatiCF
expectedIB
1
1
(s)
)(
(44)
where CF
IB(expected)
(Hz) is calculated from Equation 30,
accumulation time is calculated from Equation 33, and the line
period is determined from the period register according to
Equation 34.
For this example:
Meter Constant: MeterConstant(imp/Wh) = 3.2
Test Current: I
b
= 10 A
Line Voltage: V
nominal
= 220 V
Line Frequency: f
l
= 50 Hz
Half Line Cycles: LINECYC
IB
= 2000
CF Numerator: CFNUM = 0
CF Denominator: CFDEN = 489
Energy Reading at Base Current:
LAENERGY
IB (nominal)
= 17174
Period Register Reading: PERIOD = 8959
Clock Frequency: CLKIN = 3.579545 MHz
CF
expected
is calculated to be 1.9556 Hz according to Equation 30.
LAENERGY
expected
is calculated to be 19186 using Equation 44.
CF
IB(expected)
(Hz) =
)cos(
s/h3600
A10V220imp/Wh200
.3
ϕ×
××
= 1.9556 Hz
LAENERGY
IB(expected)
=
INT














×
+
+
×××
WDIV
CFDEN
CFNUM
CLKINPERIODLINECYCCF
IB
expectedIB
1
1
/82/
)(
LAENERGY
IB(expected)
=
INT
1
1489
1
)10579545.3/(889592/20009556.1
6












+
××××
=
19186)4.19186( =INT
WGAIN is calculated to be 480 using Equation 43.