True-rms Thermal Multimeter
Basic Measurements
25
Diode Test
XW Warning
To prevent possible electrical shock, fire, or
personal injury, disconnect power and
discharge all high-voltage capacitors before you
measure resistance, continuity, capacitance, or
a diode junction.
You can test diodes, transistors, silicon-controlled rectifiers
(SCRs), and other semiconductor devices with the Multimeter.
The test function sends a current through the semiconductor
junction and then measures the voltage drop across the
junction. A good silicon junction drops between 0.5 V and
0.8 V.
For a diode test on a diode out-of-circuit, set up the Multimeter
as shown in Figure 11. For forward-bias measurements on a
semiconductor component, put the red test lead on the
positive terminal of the component and put the black test lead
on the negative terminal of the component.
In a circuit, a good diode has a forward-bias measurement of
0.5 V to 0.8 V. A reverse-bias measurement includes the
resistance of other pathways between the probes.
A short beep sounds if the diode is good (<0.85 V). A
continuous beep sounds if the measurement is ≤0.100 V or
short circuit. The display shows OL if the diode is open.
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