Installation
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MXD75 Installation Guide
Installation
Noise suppression
In common with other electronic circuitry, the instrument 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 instrument 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 instrument 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.
In cases of very high background RF and HF noise environments, LTH can supply a
length of proprietary RF suppressing mains cable.
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