Diode Test - Mastech MS8265 Operator's Instruction Manual

Resistance is an opposition to current flow.
The unit of resistance is the ohm ( ).
The Meter's resistance ranges are 200.00Ω,
2.0000kΩ, 20.000kΩ, 200.00kΩ, 2.0000MΩ,
20.000MΩ and 200.00MΩ.
To measure resistance:
1. Set the rotary switch to proper range.
2. Connect the black and red test leads to the COM
and Ω terminals respectively.
3. Connect the test leads to the circuit being
measured and read the displayed value.
Some tips for measuring resistance:
• The measured value of a resistor in a circuit is often
different from the resistor's rated value. This is
because the Meter's test current flows through all
possible paths between the probe tips.
• In order to ensure the best accuracy in measurement
of low resistance, short the test leads before
measurement and memory the test probe resistance
in mind. This necessary to subtract for the resistance
of the test leads.
• The resistance function can produce enough voltage
to forward-bias silicon diode or transistor junctions,
causing them to conduct. To avoid this, do not use the
2M range for in-circuit resistance measurements.
• On 20MΩ and 200MΩ ranges, the meter may take
a few seconds to stabilize reading. This is normal
for high resistance measuring.
• When the input is not connected, i.e. at open circuit,
the figure "1" will be displayed for the over range
condition.
Ω
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3.2.3 Diode Test

To avoid electrical shock and/or damage to the
instrument, disconnect circuit power and
discharge all high-voltage capacitors before
testing diodes.
Use the diode test to check diodes, and other
semi- conductor 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 a diode out of a circuit:
1. Set the rotary switch to
2. Connect the black and red test leads to the COM
and terminals respectively.
3. For forward-bias 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.
4. The meter will show the approx. forward voltage of
the diode. If the test lead connection is reversed,
only figure "1" displayed.
In a circuit, a good diode should still produce a forward
bias reading of 0.5V to 0.8V; however, the reverse-bias
reading can vary depending on the resistance of other
pathways between the probe tips.
range.
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