ade7760 Analog Devices, Inc., ade7760 Datasheet - Page 18

• Manufacturer Part Number: ade7760
• Description: Energy Metering Ic With On-chip Fault Detection
• Manufacturer: Analog Devices, Inc.

ADE7760
Calibration Concerns
Typically, when a meter is being calibrated, the voltage and
current circuits are separated as shown in Figure 25. This means
that current passes through only the phase or neutral circuit.
Figure 25 shows current being passed through the phase circuit.
This is the preferred option, because the ADE7760 starts billing
on the input V
nected to V
neutral circuit, the FAULT indicator comes on under these
conditions. However, this does not affect the accuracy of the
calibration and can be used as a means to test the functionality
of the fault detection.
CURRENT
TEST
Figure 25. Fault Conditions for Inactive Input Greater than Active Input
IB
IB
1A
240V RMS
in the diagram. Because there is no current in the
1A
V
on power-up. The phase circuit CT is con-
AGND
RA*
RB*
VR*
*RB + VR = RF
CT
CT
RB
RB
C
F
R
0V
V
F
1A
C
R
R
T
F
F
V
V
2P
2N
C
C
F
F
V
V
V
1A
1N
1B
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If the neutral circuit is chosen for the current circuit in the
arrangement shown in Figure 25, this may have implications for
the calibration accuracy. The ADE7760 powers up with the V
input active as normal. However, because there is no current in
the phase circuit, the signal on V
be flagged and the active input to be swapped to V
The meter can be calibrated in this mode, but the phase and
neutral CTs might differ slightly. Because under no-fault condi-
tions all billing is carried out using the phase CT, the meter
should be calibrated using the phase circuit. Of course, both
phase and neutral circuits can be calibrated.
1A
is zero. This causes a fault to
1B
(neutral).
1A