User manual for meter with U/I input PD72S
Due to possible significant interference in industrial installations appropriate measures
assuring correct operation of the unit must be applied. To avoid the unit of improper
indications keep recommendations listed below.
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Avoid common (parallel) leading of signal cables and transmission cables together
with power supply cables and cables controlling induction loads (e.g. contactors).
Such cables should cross at a right angle.
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Contactor coils and induction loads should be equipped with anti-interference
protection systems, e.g. RC-type.
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Use of screened signal cables is recommended. Signal cable screens should
be connected to the earthing only at one of the ends of the screened cable.
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In the case of magnetically induced interference the use of twisted couples of signal
cables (so-
called “spirals”) is recommended. The spiral (best if shielded) must be
used with RS-485 serial transmission connections.
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In the case of interference from the power supply side the use of appropriate anti-
interference filters is recommended. Bear in mind that the connection between the
filter and the unit should be as short as possible and the metal housing of the filter
must be connected to the earthing with largest possible surface. The cables
connected to the filter output must not run in parallel with cables with interference
(e.g. circuits controlling relays or contactors).
Connections of power supply voltage and measurement signals are executed using the screw
connections on the back of the
unit’s housing.
Figure 4.4. Method of cable insulation replacing and cable terminals
9
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If the unit is equipped with housing, covers and sealing packing, protecting against
water intrusion, pay special attention to their correct tightening or clamping. In the
case of any doubt consider using additional preventive measures (covers, roofing,
seals, etc.). Carelessly executed assembly can increase the risk of electric shock.
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After the installation is completed do not touch the unit’s connections when it is
switched on, because it carries the risk of electrical shock.
