LTH Electronics MTD75, Operation Manual

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Installation
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MTD75 Operation Guide
Ins
tallation
Noise suppression
In common with other electronic circuitry, the controller 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 controller in an
environment where such interference could potentially occur.
The following noise generating sources can affect the controller 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 controller 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 controller’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 controller.

In cases of very high background RF and HF noise environments, LTH can supply a
length of proprietary RF suppressing mains cable.