Datasheet

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71M6515H

Energy Meter IC

DATA SHEET

JULY 2011

A Maxim Integrated Products Brand

Name

Description

CAL_IA

Gain factors for current and voltage of each phase.

CAL_VA

CAL_IB

CAL_VB

CAL_IC

CAL_VC

TEMP_NOM

The value of TEMP_RAW at nominal temperature.

PHADJ_A

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.

PHADJ_B

PHADJ_C

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.