2 Making Measurements
Testing Diodes
80 U1271A/U1272A User’s Guide
Testing Diodes
Use the diode test to check diodes, transistors, silicon
controlled rectifiers (SCRs), and other semiconductor
devices. A good diode allows current to flow in one direction
only.
This test sends a current through a semiconductor junction,
and then measures the junction’s voltage drop. A typical
junction drops 0.3 V to 0.8 V.
1 To test a diode out of a circuit, position the rotary switch
to / and set up your multimeter as shown in
Figure 2- 21.
2 Probe the test points and read the display.
Figure 2-19 Diode display
To avoid possible damage to your multimeter or to the equipment under
test, disconnect the circuit power and discharge all high-voltage
capacitors before testing diodes.
Connect the red test lead to the positive terminal (anode) of the diode and
the black test lead to the negative terminal (cathode). The cathode of a
diode is indicated with a band.
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