Preliminary Adjustments; Internal Battery Condition; Dc Voltage Measurement - Gardner Bender GMT-12A Manuel D'utilisation

4) When the meter 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 meter
housing. Never pull the leads out of the jacks by the
insulated wire or transport the meter using the test leads
as a carrying strap.
6) Never immerse the meter 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 meter 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
counterclockwise until the needle indicator is directly over
the three black zeros at the left end of the scale.
Analog Meter: Reading the Scale
5K
100
2K 200
500
10K
1K
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8
AC Voltage Scale
dB Scale for Transistor
Gain Measurement
General
The first step in reading the analog scale is to align the
needle with the scale. This is achieved by locating the
mirror on the scale. Line the needle up with its reflection.
When the reflection is hidden by the needle, the needle
is properly aligned.
Resistance
50
(Ohms)
20
10
Scale
DC Voltage
& Milliamps
Scale
Common Markings
for both the AC &
DC Voltage Scales
5
Resistance (Ohms - Ω)
Use the top scale for reading the resistance. If the meter
is set to X1k, multiply the resistance value by 1000Ω.
DC Voltage (V DC)
Use the middle scale directly below the mirror. Match the
dial setting to the highest number on the scale. If the setting
does not match one of the numbers, use a scale that can be
easily multiplied to give the setting (i.e. - for 500V, use the
50V scale and multiply the reading by 10).
AC Voltage (V AC)
Use the same numbers and procedures as used for
the DC voltage setting, but use the scale directly below
the numbers.
DC Milliamps
Use the same scale and procedure as used for the DC
voltage setting.
Decibel Gain (dB)
- see pg. 15
Use the scale marked dB to read decibels. Use the chart
at the right of the scale for proper conversion.

3.2 Internal Battery Condition

Before making resistance or continuity tests, check the
condition of the internal battery. First turn the function/range
switch to the ohms Rx1K 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 simultaneously turning the zero ohms adjustment
dial until the needle indicator reads zero at the right side
of the ohms (green) scale. If the needle will not zero,
replace the battery with a new 1.5 volt AA size battery
(see Battery Replacement).

4. DC Voltage Measurement

1) Fully seat the test leads in the correct input jacks, (-) black
lead, (+) red lead.
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