Measuring Diodes & Continuity - UNI-T UT39A Operating Manual

Model UT39A/B/C: OPERATING MANUAL
I. Measuring Diodes & Continuity
Warning
To avoid damage to the Meter or to the equipment
under test, disconnect circuit power and discharge
all high-voltage capacitors before measuring diodes
and continuity.
Never attempt to input over 60V in DC or 3V rms in
AC to avoid personal dangerous.
Testing Diodes
Use the diode test to check diodes, transistors, and other
semiconductor devices. The diode test sends a current
through the semiconductor junction, and then measures
the voltage drop across the junction. A good silicon
junction drops between 0.5V and 0.8V.
To test out a diode out of a circuit, connect the Meter as
follows:
1. Insert the red test lead into the V
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 red test lead on
the component's anode and place the black test lead
on the component's cathode.
The LCD displays the nearest value of diode forward
voltage drop.
Note
l
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 depending on
the resistance of other pathways between the probe
tips.
l
Connect the test leads to the proper terminals as said
above to avoid error display. The LCD displays "1"
indicating open-circuit for wrong connection. The unit
of diode is Volt (V), displaying the positive-connection
voltage-drop value.
l
When diode testing has been completed, disconnect
the connection between the testing leads and the
circuit under test.
terminal and the
.
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