26
Rotate the function switch between the two
DC positions to reverse polarity. This will
determine if there is a difference between
the resistance in the two directions.
To check a semiconductor in or out of a
circuit (forward and reverse bias resistance
measurements) consider the following
be-
fore making the measurement:
a.
The polarity of the internal ohmmeter
battery voltage will be as marked at
the jacks when the switch is in the +DC
position and reversed in the -DC posi-
tion.
b.
Ensure that the range selected will not
damage the semiconductor. (Refer to
Table 1-1, item 8, and review the speci-
fication limits of the semiconductor ac-
cording to the manufacturer’s ratings.)
c.
If the semiconductor is a silicon diode
or conventional silicon transistor, pre-
cautions are not normally required.
d.
If the semiconductor material is germanium, check the ratings of the device
and refer to Table 1-1, item 8.
NOTE:
The resistance of diodes will measure differently from one resistance
range to another on the VOM with the function switch in a given position. For
example, a diode which measures 80 ohms on the R X 1 range may mea-
sure 300 ohms on the R X 100 range. The difference in values is a result of
the diode characteristics and is not indicative of any fault in the VOM.
4.13 Continuity Tests
Turn off all power to the circuit under test
before proceeding any further.
a.
Set the FUNCTION switch to the “ ”.
Insert the black test lead into the COM-
MON (-) and the red test lead into the
(+) jacks, (Figure 4-14).
b.
Touching the test lead probe tips to-
gether should produce an audible
sound
c.
To test for continuity, probe the circuit
or component in question. An audible
sound indicates continuity.
d.
The higher the circuit’s resistance, the
lower the sound level. The lower the
circuit’s resistance, the higher the
sound level.
e.
Refer to Paragraph 4.12, Figure 4-13
for measurements of circuit resistance, if any, that exists.
Figure 4-13. Jacks and Switch
Positions for Measuring Resistance
R x 1
R x I0,000
ZERO OHMS
+
COMMON
-
- D.C.
+ D.C.
OHMS
OH
MS
260
ALL TERMINALS 1 V MAX
R X I00
Figure 4-14. Jacks and Switch
Positions for Continuity Tests
R x 1
R x I0,000
ZERO OHMS
+
COMMON
-
- D.C.
+ D.C.
OHMS
OHMS
260
ALL TERMINALS 1 V MAX
R X I00
!
www.calcert.com
1.888.610.7664
0
5
10
15
20
25
30