Datasheet

Data Sheet ADE7758
Rev. E | Page 47 of 72
START
STEP 1
ENABLE CF
OUTPUTS
STEP 2
CLEAR OFFSET
REGISTERS
xWATTOS, xVAROS
ALL PHASES
WATT OFFSET
CALIBRATED?
YES NO
ALL PHASES
VAR OFFSET
CALIBRATED?
YES NO
SET UP APCF
PULSE OUTPUT
FOR PHASE A, B,
OR C
STEP 4
STEP 3
SET UP SYSTEM
FOR I
MIN
,V
NOM
,
PF = 1
STEP 5
MEASURE %
ERROR FOR
APCF
STEP 6
CALCULATE AND
WRITE TO
xWATTOS
END
SET UP VARCF
PULSE OUTPUT
FOR PHASE A, B,
OR C
STEP 4
STEP 3
SET UP SYSTEM
FOR I
MIN
,V
NOM
,
PF = 0, INDUCTIVE
STEP 5
MEASURE %
ERROR FOR VARCF
MEASURE PERIOD
USING FREQ[11:0]
REGISTER
STEP 6
CALCULATE AND
WRITE TO
xVAROS
STEP 7.
REPEAT STEP
3TOSTEP6
FOR xVAROS
SELECT PHASE
FOR LINE PERIOD
MEASUREMENT
CONFIGURE
FREQ[11:0] FOR A
LINE PERIOD
MEASUREMENT
04443-079
Figure 80. Offset Calibration Using Pulse Output
Step 1: Repeat Step 1 and Step 3 from the gain calibration to
configure the ADE7758 pulse output.
Step 2: Clear the xWATTOS and xVAROS registers.
Step3: Disable the Phase B and Phase C contribution to the APCF
and VARCF pulses. This is done by the TERMSEL[2:4] bits of
the COMPMODE register (0x16). Setting Bit 2 to Logic 1 and
Bit 3 and Bit 4 to Logic 0 allows only Phase A to be included in
the pulse outputs. Select Phase A, Phase B, or Phase C for a line
period measurement with the FREQSEL[1:0] bits in the MMODE
register (0x14). For example, clearing Bit 1 and Bit 0 selects
Phase A for line period measurement.
Step 4: Set the test system for I
MIN
, V
NOM
, and unity power factor.
For Step 6, set the test system for I
MIN
, V
NOM
, and zero-power
factor inductive.
Step 5: Measure the percent error in the pulse output, APCF or
VARCF, from the reference meter using Equation 49.
Step 6: Calculate xWATTOS using Equation 56 (for xVAROS
use Equation 57).
APCFNUM
APCFDEN
Q
APCF
%APCF
xWATTOS
EXPECTED
ERROR
××
⎟
⎠
⎞
⎜
⎝
⎛
×
=
4
2
%100
–
(56)