5
6
3.2 Check Condition of Internal Battery
Before making resistance or continuity tests, check the
condition of the internal battery. First turn the function/range
switch to an ohms position. Short the test leads together and
the needle indicator should deflect to the right side of the
scale. Keep the test leads shorted together while simul-
taneously turning the zero ohms adjustment dial until the
needle indicator reads zero at the right side of the ohms scale.
If the needle will not zero, replace the batteries with two new
1.5 volt AA size batteries (see Battery Replacement ).
1) Fully seat the test leads in the correct input jacks, (-) black
lead, (+) red lead.
2) Set the function/range switch to the appropriate DC
voltage range. If the voltage is unknown, use the highest
range. If the voltage applied falls within the range of a
lower setting, reset the function/range switch to the
appropriate setting for greatest accuracy of reading.
3) If the polarity of the circuit to be tested is known, touch the
black test lead to the neutral side. If the polarity is
unknown, touch the test leads to opposite sides of the
circuit. If the needle indicator deflects to the left of the
scale, reverse the test leads.
Use the chart below as a guide to reading DC
voltage measurements:
DCV
Read
and
range
following
multiply
setting
scale
reading by:
2.5
0-250
divide reading by 100
50
0-50
1
250
0-250
1
1000
0-10
100
2) Avoid placing the tester in areas where vibration, dust or
dirt are present. Do not store the tester in excessively
hot, humid or damp places. This tester is a sensitive
measuring device and should be treated with the same
regard as other electrical and electronic devices.
3) Using the tester in areas with high magnetic fields can
result in inaccurate readings. For greatest accuracy of
reading, lay the tester flat on a non-metallic surface.
4) When the tester is not in use, keep the function/range
switch in the OFF position. This keeps the needle indicator
from deflecting or “bouncing” excessively.
5) When disconnecting the test leads from the unit, always
grasp the leads where the input jacks meet the tester
housing. Never pull the leads out of the jacks by the
insulated wire or transport the tester using the test leads
as a carrying strap.
6) Never immerse the tester in water or solvents. To clean
the housing use a damp cloth with a minimal amount of
mild soap.
7) If the resistance (ohms) function of the tester is not going
to be used for a week or more, remove the internal battery
to avoid potential leaks that may damage the unit.
3.1 Preliminary Adjustments
Fully seat the test leads in the correct input jacks. If
necessary, using a small flat tip screwdriver, slowly turn the
mechanical zero adjustment screw clockwise or counter-
clockwise until the needle indicator is directly over the three
black zeros at the left end of the scale.
DC
10
20
50
100
200
500
2K
5K
10K
6
8
1K
Resistance
(Ohms)
Scale
DC Voltage
& Milliamps
Scale
Common Markings
for both the AC &
DC Voltage Scales
AC Voltage Scale
dB Scale for Transistor
Gain Measurement
}
4.0 DC Voltage Measurement
Summary of Contents for GMT-18A
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