ITRON Centron, Technical Reference Manual

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Operation: Base Metrology
CENTRON® Meter Technical Reference Guide 19
The custom ASIC cancels all the offset generated by the meter and removes the need for a
light load adjustment of the metrology. This allows the meter to have excellent accuracy
over a very large dynamic range, especially at the low current levels. For this reason, no
offset adjustment is needed or provided for the CENTRON meter.
There is a slight phase shift in the current to flux density conversion due to eddy currents in
the magnetic core material. This shift causes a small power factor error that is uniform
across the dynamic range (load curve) of the meter. Itron compensates for this shift in the
CENTRON by the use of a capacitor in the biasing current circuit. This correction is
permanent.
The custom ASIC provides:

Wh pulses to drive the Test LED
The same signal is also provided to the electronic register attachments.

energy direction (sign)

60Hz clock signal synchronized with the line voltage (for time keeping)

pulse that drives the stepper motor for the mechanical register attachment (1 pulse every
10 watthours)
The metrology board, which houses the measurement components described above, passes
the Wh pulse, energy direction, and 60Hz clock signals to the personality module attached
to the meter base. The two line voltages (one is referred to as meter ground), and power
supply references are also supplied for reference purposes.
An inherent feature built into the design of each CENTRON ensures that the
calibration of the product is not affected by any electronic board (existing or
planned) added to the meter. This is achieved by a distributed power supply and
documented design requirements in the CENTRON developer’s kit.
CENTRON 2S CL320, 4S, 12/25S
The advanced metering forms of the CENTRON (2S CL320, 4S, and 12/25S) meter use the
same Hall Effect measurement principle that is used in the form 1S, 2S, and 3S metering
forms described earlier.
The major difference with these metering forms is the presence of two Hall cells, magnetic
cores, and ADCs (see the Hall Cells and ADCs figure below).
For these metering applications, the biasing current Ibias ( Ibias1 and Ibias2 ) applied to each
sensor is generated from the line voltage ( Vline1 and Vline2 ) using a resistor. The magnetic
field is generated by the line current ( Iline1 and Iline2 ) that flows through the conductor
looped around each core. The voltage ( Vout1 and Vout2 ) that is formed on each Hall Effect
device is proportional to the watts produced by each phase.