Despatch MIC1462 Controller Manual - Manual (Page 12)

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1. If the instrument is to be mounted in the same panel as any of the listed devices,
separate them by the largest distance possible. For maximum electrical noise
reduction, the noise generating devices should be mounted in a separate enclosure.
2. If possible, eliminate mechanical contact relay(s) and replace with solid state relays.
If a mechanical relay being powered by an instrument output device cannot be
replaced, a solid state relay can be used to isolate the instrument.
3. A separate isolation transformer to feed only instrumentation should be considered.
The transformer can isolate the instrument from noise found on the AC power input.
4. If the instrument is being installed on existing equipment, the wiring in the area
should be checked to insure that good wiring practices have been followed.
AC POWER WIRING
Neutral (For 115 VAC)
It is good practice to assure that the AC neutral is at or near ground potential. To verify
this, a voltmeter check between neutral and ground should be done. On the AC range,
the reading should not be more than 50 millivolts. If it is greater than this amount, the
secondary of this AC transformer supplying the instrument should be checked by an
electrician. A proper neutral will help ensure maximum performance from the
instrument.
WIRE ISOLATION
Four voltage levels of input and output wiring may be used with the unit:
•
Analog input or output (i.e. thermocouple, RTD, VDC, mVDC, or mADC)
•
SPDT Relays
•
SSR driver outputs
•
AC power
The only wires that should run together are those of the same category. If they need to
be run parallel with any of the other lines, maintain a minimum 6 inch space between
wires. If wires must cross each other, do so at 90 degrees. This will minimize the
contact with each other and reduces "cross talk". "Cross Talk" is due to the EMF
(Electro Magnetic Flux) emitted by a wire as current passes through it. This EMF can
be picked up by other wires running in the same bundle or conduit.
In applications where a High Voltage Transformer is used (i.e. ignition systems) the
secondary of the transformer should be isolated from all other cables.