User manual for flow meter with pulse input SPI-94
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.
–
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.
–
Contactor coils and induction loads should be equipped with anti-interference protection
systems, e.g. RC-type.
–
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.
–
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.
–
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
All connections must be made while power supply is disconnected !
10
m
ax
. 2 m
m
6-7 mm
!
