71M6513/71M6513H Demo Board User’s Manual
Page: 46 of 112
©
2005-2006 TERIDIAN Semiconductor Corporation
Revision 5.6
10.
)
sin(
)
60
tan(
)
cos(
2
180
0
300
60
S
S
E
E
E
E
φ
φ
+
+
=
−
11.
)
tan(
)
60
tan(
)
2
(
180
0
300
60
S
E
E
E
E
φ
+
+
=
−
12.
Î
+
+
−
=
−
)
2
)(
60
tan(
)
(
tan
180
0
300
60
1
E
E
E
E
S
φ
Now that we know the A
XV
, A
XI
, and
φ
S
errors, we calculate the new calibration voltage gain coefficient from the
previous ones:
XV
NEW
A
V
CAL
V
CAL
_
_
=
We calculate PHADJ from
φ
S
, the desired phase lag:
[
]
[
]
−
−
−
−
−
−
−
+
=
−
−
−
−
)
2
cos(
)
2
1
(
1
)
tan(
)
2
sin(
)
2
1
(
)
2
cos(
)
2
1
(
2
)
2
1
(
1
)
tan(
2
0
9
0
9
0
9
2
9
20
T
f
T
f
T
f
PHADJ
S
S
π
φ
π
π
φ
And we calculate the new calibration current gain coefficient, including compensation for a slight gain increase
in the phase calibration circuit.
2
9
0
9
0
9
20
20
)
2
1
(
)
2
cos(
)
2
1
(
2
1
))
2
cos(
)
2
1
(
2
2
2
(
2
1
1
_
_
−
−
−
−
−
−
+
−
−
−
−
+
+
=
T
f
T
f
PHADJ
PHADJ
A
I
CAL
I
CAL
XI
NEW
π
π
2.2 CALIBRATION PROCEDURES
Calibration requires that a calibration system is used, i.e. equipment that applies accurate voltage, load current
and load angle to the unit being calibrated, while measuring the response from the unit being calibrated in a
repeatable way. By repeatable we mean that the calibration system is synchronized to the meter being
calibrated. Best results are achieved when the first pulse from the meter opens the measurement window of the
calibration system. This mode of operation is opposed to a calibrator that opens the measurement window at
random time and that therefore may or may not catch certain pulses emitted by the meter.
It is essential for a valid meter calibration to have the voltage stabilized a few seconds
before the current is applied. This enables the Demo Code to initialize the 71M6513/6513H
and to stabilize the PLLs and filters in the CE. This method of operation is consistent with
meter applications in the field as well as with metering standards.
Each meter phase must be calibrated individually. The procedures below show how to calibrate a meter phase
with either three or five measurements. The PHADJ equations apply only when a current transformer is used for
the phase in question. Note that positive load angles correspond to lagging current (see Figure 2-2).
During calibration of any phase, a stable mains voltage has to be present on phase A. This
enables the CE processing mechanism of the 71M6513/6513H necessary to obtain a stable
calibration.
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