71M6515H
Energy Meter IC
DATA SHEET
MARCH 2008
Name
Description
CAL_IA
CAL_VA
CAL_IB
CAL_VB
CAL_IC
Gain factors for current and voltage of each phase.
CAL_VC
TEMP_NOM
PHADJ_A
PHADJ_B
PHADJ_C
The value of TEMP_RAW at nominal temperature.
Phase compensation for each current. If phase compensation is 0 or if
current sensors have predictable phase, PHADJ may not need to be
measured on every meter.
Table 4: Typical Calibration Parameters (CT)
Gain adjustment (CAL_Xn parameters) is used to compensate for tolerances of components used for signal conditioning,
especially the resistive components. A 1% increase in CAL_Xn will cause a 1% increase in the channel gain.
The phase compensation circuit in the TERIDIAN 71M6515H is optimized for operation with current transformers (CT’s). These
devices have a low frequency pole and therefore have a slight amount of phase lead at 50 or 60Hz—more at 50Hz than at
60Hz. The phase lead diminishes at higher harmonics. When PHADJ_n is calibrated as shown below at either 50Hz or 60Hz,
the CT will be correctly compensated from below 25Hz to beyond 1100Hz.
This phase compensator is markedly superior to the more common technique of programming a time delay to compensate for
CT phase. The time delay technique results in phase compensation that is correct at only one frequency, and actually amplifies
the phase error at harmonics of the frequency.
Calibration Factors for Rogowski Coil Sensors
If IMAGE is set to 01, i.e. the 71M6515H can be operated with Rogowski Coil sensors. In this case, one more calibration factor
per phase is needed. The PHADJ parameters have non-zero defaults and do not obey the same formula used for CT
calibration. The feedthrough parameter has to be determined by a separate crosstalk measurement. Table 5 shows the
parameters involved in the calibration procedure for the Rogowski sensor.
Name
Description
CAL_IA
CAL_VA
CAL_IB
CAL_VB
Gain constants for current and voltage of each phase.
CAL_IC
CAL_VC
TEMP_NOM
PHADJ_A
PHADJ_B
PHADJ_C
VFEED_A
VFEED_B
VFEED_C
The value of TEMP_RAW at nominal temperature.
Phase compensation for each current. If phase compensation is 0 or if
current sensors have predictable phase, PHADJ may not need to be
measured on every meter.
Feedthrough compensation for each current.
Table 5: Typical Calibration Parameters (Rogowski)
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