ELECTRICAL SYSTEM
128
Diodes
What is a diode? A diode acts like a one way valve,
allowing current to flow in only one direction.
See Figure 7.54.
Which way does this electrical check-valve work?
There will be a band on one end of the diode. The band
indicates the negative side of the diode
• Most DVOMs have the ability to test a diode.
Testing a diode:
1. Isolate the diode in the circuit.
2. Set the DVOM to the diode or Ω scale.
See Figure 7.55.
3. Attach the negative lead of the DVOM to the side
of the diode with a band on it.
4. Place the positive lead on the other side of the
diode.
5. There should be continuity. See Figure 7.56.
6. Switch the leads.
7. The meter should indicate no continuity.
See Figure 7.57.
8. If the results do not match the above, replace the
diode.
Figure 7.54
Silver band
(-)
(+)
electrons flow from the negative to the positive.
Figure 7.55
Diode scale
Figure 7.56
Continuity
Silver band
(-)
(+)
Figure 7.57
No continuity
Silver band
(-)
(+)
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