Testing Diodes - UNI-T UT70D Operating Manual

E. Testing Diodes
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
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.
Note
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
8
(see figure 9)
.
23
terminal