Checking Diodes; Measuring Logic - Radio Shack 22-812A Manual

Checking Diodes

You can check diodes, transistors, and other semiconductors for opens, shorts,
and normal operation, and determine the forward �oltage and polarity for diodes.
You can also check LeDs.
1. power off the circuit under test and discharge all capacitors.
2. Rotate the function dial to
3. Connect the test leads to the de�ice you want to check, or remo�e one of
the leads of the component from its circuit and connect the test leads to the
component. Note the first reading.
4. Re�erse the test leads and note the second reading.
if one reading shows a �alue and the other is o�errange (OF appears) the de�ice
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is good. if OF appears during both readings, the de�ice is open. if both �alues are
very small or zero, the device is shorted.
Notes:
• when you test a silicon-type semiconductor, the �alues might �ary depending on the
temperature.
• The �alues that appear during a diode check show the actual forward �oltage (2.0V
ma�). if the �oltage e�ceeds 2.0V,
• To check polarity of an unmarked diode: C
sides of the diode. Measure and note the �oltage. Then, re�erse the test
leads, measure and note the second reading. The side of the diode where
the meter shows a higher �oltage using the red test lead is the anode (+)
side. The side of the diode where the meter shows OF using the red test lead
is the cathode (–) side.

Measuring Logic

WARNING: Do �OT apply more than 5 V DC between terminals. This could
damage the meter or the circuit being tested.
1. Rotate the function dial to LOGIC/Hz and press SELECT once. LO appears.
2. Connect the test leads to the de�ice you want to check.
LO appears if the logic is low (the �oltage is lower than 1.0V). Hi appears if the
logic is high (the �oltage is higher than 2.0V) The actual �oltage appears if the
logic is between 1 and 2 V.
Taking Measurements
/
and press SELECT.
OF
appears. The meter cannot check this diode.
onnect the test leads to the two
1
appears.