SeaSTAR 3510LR Manual do Utilizador descarregar pdf (Página 20)

SeaSTAR 3510LR USER MANUAL

Issue 1.0 11/04

Counter Electromagnetic Force (CEMF)

A potential problem inherent in any installation of electronic systems within a

vehicle is Counter Electro-magnetic Force (CEMF).

CEMF is caused when relays or solenoids, connected to the vehicle DC power

distribution, are de-energised. The voltage produced may exceed – 400 volts.

CEMF is produced by equipment such as the following:

• Electric fan brakes

• Air conditioners

• Starter relays

• Electric pump relays

CEMF is more than sufficient to damage or cause erratic operation of any

electronic system that is also connected to the same vehicle DC power supply.

CEMF can be eliminated by installing diodes at the relays and solenoids that

cause the problem, and more importantly at the power supply cable connections

on the receiver.

A 47V, 5W, Zener diode (1N5368 or equivalent) should be connected between the

receiver +ve (positive) power input terminal and ground, as illustrated in Figure 5.

Figure 5. Zener Diode Connected

Ground

Battery +ve (positive) supply

Zener Diode

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