AMETEK 1995A Micro-Set PLS - Manual (Page 28)

Chapter 8: Troubleshooting
Installation and Maintenance Manual 24
The 1995 PLS is designed for use in an industrial environment and incorporates extensive transient
suppression circuitry. However, the same general installation rules should be followed that apply to all
microprocessor-based equipment.
Problems that can be attributed to extreme electrical noise or poor power quality include loss of/or
changes in program memory, loss of initialization, keypad or microprocessor lockup, sporadic outputs,
and damage to resolver drive circuits and auxiliary input circuits.
8.3: Electrical Noise and Power Quality Consideration
8.4: Grounding
Circuit board level noise suppression circuits, ground planes, and cable shields all depend on a good
earth ground for proper operation. Our field experience has shown that the quality of the service
ground at many machines is marginal.
8.5: Incoming Power
Solenoids, welders, large motors, and variable-speed drives are all devices that generate excessive
electrical noise throughout the power grid in a typical industrial environment. Isolation transformers or
constant voltage type power supplies should be used to isolate microprocessor-based circuitry. The
power on the output side of these isolation devices should be fed to the programmable limit switch and
other microprocessor-based devices only. The loads being driven by the programmable limit switch
output relays must not get their power from the output side of the isolation device. Using the output
side of an isolation device to power loads other than the programmable limit switch totally defeats the
purpose of the isolation device.
NOTE: When using an output relay for driving inductive loads such as solenoids, a noise suppression
device must be installed across the coil of the load. Use an MOV or RC noise suppressor
for AC loads, or a commutating diode for DC loads.
8.6: Low Level Inputs
Low level inputs to the 1995A PLS include the resolver cable and other special purpose contact inputs
such as reset-to-preset, fault check, and security.
The resolver should be wired to the 1995 PLS using an uninterrupted run of cable consisting of four
twisted pairs with shields. Whenever possible, this cable should be run in a conduit by itself. If it must
run in a conduit with other wiring, this wiring should not include power wires above 110V AC or wires
driving noise producing loads.