Measuring System; Input Signals - Landis+Gyr E650 Series User Manual

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Communication unit
2.5

Measuring system

2.5.1

Input signals

ZMD300xT
Voltage input
Current input
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The communication unit for fitting only in the ZMD300xT meters is a
complete unit in its own case. If present, it is situated behind the front door,
and is therefore secured by a utility seal and can be exchanged or inserted
in the field if necessary. It contains:

Communication interfaces as required for remote readout of the meter
(e.g. CS, RS232, RS485, modem)

Two signal inputs (S0 interfaces) for processing external pulse
transmitters
Figure 2. Block schematic diagram of measuring system
The meter has the analogue current values I1, I2 and I3 and analogue
voltage values U1, U2 and U3 available as input signals.
Figure 3. Type of measurement ZMD300xT
Since the ZMD300xT measures the individual phases mutually
independently with one measuring element each, it can record the sum of
the three phases, the individual phases themselves, the phase angle
between voltage and current as well as the angle between voltages U1–U2
and U1–U3.
High resistance voltage dividers reduce the voltages U1, U2 and U3 (58 to
240 V) applied to the meter to a proportionate amount of a few mV (U
further processing.
Internal current transformers reduce the input currents I1, I2 and I3 to the
meter (0 to 10 A) for further processing. The secondary currents of these
current transformers develop voltages proportional to the input currents
across resistors, also of a few mV (U ).
I
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Device description
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