User's Manual

Operation: Base Metrology
3-4 CENTRON Meter Technical Reference Guide
For these metering applications, the biasing current Ibias (I
bias1
and I
bias2
) applied to
each sensor is generated from the line voltage (V
line1
and V
line2
) using a resistor. The
magnetic field is generated by the line current (I
line1
and I
line2
) that flows through the
conductor looped around each core. The voltage (V
out1
and V
out2
) that is formed on
each Hall Effect device is proportional to the watts produced by each phase.
Each Hall sensor output voltage is amplified by a differential amplifier in order to
bring the signal within the nominal level of the ADC. ADC 1 sums the signal from
ADC 1 and ADC 2. The output of ADC 1 is integrated over time to get the energy
information. Each time the integrated signal exceeds a predetermined amount of
energy, a pulse is generated. The pulse stream is accumulated into a counter. When
the accumulated pulses reach a threshold, a Wh pulse is emitted and the meter
LED is flashed. The counter threshold is programmed at the factory and serves as
the permanent gain calibration for the life of the product. The calibration is a
digital feature and has no variation or adjustment. ADCs 1 and 2 are calibrated
independently, which means that each phase is calibrated independently.
Figure 3.3 Hall Cells and ADCs