2 Installation – Safety & EMC
8
Noise suppression
In common with other electronic circuitry, the MOD53 may be affected by high level,
short duration noise spikes arising from electromagnetic interference (EMI) or radio
frequency interference (RFI). To minimise the possibility of such problems occurring,
the following recommendations should be followed when installing the unit in an
environment where such interference could potentially occur.
The following noise generating sources can affect the MOD53 through capacitive or
inductive coupling.
• Relay coils
• Solenoids
• AC power wires, particularly at or above 100V AC
• Current carrying cables
• Thyristor field exciters
• Radio frequency transmissions
• Contactors
• Motor starters
• Business and industrial machines
• Power tools
• High intensity discharge lights
• Silicon control rectifiers that are phase angle fired
The MXD53 series is designed with a high degree of noise rejection built in, to
minimise the potential for interference from these sources, but it is recommended
that you apply the following wiring practices as an added precaution. Cables
transmitting low level signals should not be routed near contactors, motors,
generators, radio transmitters, or wires carrying large currents.
If noise sources are so severe that the instrument’s operation is impaired, or even
halted, the following external modifications should be made, as appropriate:
• Fit arc suppressors across active relay or contactor contacts in the vicinity.
• Run signal cables inside steel tubing as much as is practical.
• Use the internal relays to switch external slave relays or contactors when
switching heavy or reactive loads.
• Fit an in-line mains filter close to the power terminals of the instrument.
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General