UNI-T UT70D, Operating Manual

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E. Testing Diodes
(see figure 9)
To avoid damages to the Meter or to the devices
under test, disconnect circuit power and discharge
all the high-voltage capacitors before measuring
diodes.
Use the diode test to check diodes, transistors, and other
semiconductor devices. The diode test sends a current
through the semiconductor junction, then measures the
voltage drop across the junction. A good silicon junction
drops between 0.5V and 0.8V.
To test a diode out of a circuit, connect the Meter as
follows:
1. Insert the red test lead into the terminal
and the black test lead into the
COM terminal.
2. Set the rotary switch to .
3. For forward voltage drop readings on any
semiconductor component, place the
terminal (red test lead) to anode &
COM terminal
(black test lead) to cathode.
The measured value shows on the display.
In a circuit, a good diode should still produce a
forward voltage drop reading of 0.5V to 0.8V;
however, the reverse voltage drop reading can vary
Note