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VOLTAGE MEASUREMENT
Figure 3 shows a simplified diagram of the voltage
measurement function.
The input divider resistors add up 10MΩ with each
step being a division of 10. The divider output
should be withing –0.199 to +0.199V or the overload
200mV
Volts
9M
2V
900k
20V
90k
200V
9k
1kV
1k
Common
Figure 3 Simplified Voltage Measurement Diagram
CURRENT MEASUREMENT
Figure 4 shows a simplified diagram of the current
measurement positions.
Internal shunt resistors convert the current to
between –0.199 to +0.199V which is then
200µA
20mA
200µ
900
200mA
2mA
A
20A
20mA
200mA
100
20A
9Ω
1Ω
COM
Shunt
.01Ω
20A
Figure 4 Simplified Current Measurement Diagram
indicator will function. If the AC function is selected,
the divider output is AC coupled to a full wave
rectifier and the DC output is calibrated to equal the
rms level of the AC input.
DC
Low Pass
Filter
AC
7106R
100mV
Ref
AC to DC
Converter
processed in the 7106 IC to light the appropriate
LCD segments. If the current is AC in nature, the
AC converter changes it to the equivalent DC value.
2mA
DC
Low
Pass
Filter
AC
7106R
AC - DC
Converter
100mV
Ref
-3-
4. OPERATION MAINTENANCE
4-1 Battery and Fuse Replacement
CAUTION
BEFORE ATTEMPTING BATTERY REMOVAL OR
REPLACEMENT,
DISCONNECT
THE
LEADS FROM ANY ENERGIZED CIRCUITS TO
AVOID SHOCK HAZARD.
The fuse rarely needs replacement and blow almost
always as a result of operator error. To replace the
battery and fuse (2A/250V), remove the two screws
in the bottom of the case. Simply remove the old
battery or fuse and replace with a new one.
Be sure to observe the polarity when replacing the
battery.
4-2 Calibration Procedure
It is normally not necessary to recalibrate for long
intervals. If needed, adjustment should be done
with highly accurate standards (setter than 0.1%
accuracy).
5. SAFETY SYMBOLS
This marking adjacent to another marking or a
terminal operating device indicates that the
operator must refer to an explanation in the
!
operating instructions to avoid damage to the
equipment and/or to avoid personal injury.
This WARNING sign denotes a hazard. It calls
attention to a procedure, practice or the like, which
WARNING
if not correctly performed or adhered to, could result
in personal injury.
This CAUTION sign denotes a hazard.
attention to a procedure, practice or the like, which
CAUTION
if not correctly adhered to, could result in damage to
or destruction of part or all of the instrument.
This marking advises the user that the terminal(s)
so marked must not be connected to a circuit point
at which the voltage, with respect to earth ground,
500V max.
exceeds (in this case) 500 volts.
This symbol adjacent to one or more terminals
identifies them as being associated with ranges that
may in normal use be subjected to particularly
hazardous voltages.
instrument and its test leads should not be handled
when these terminals are energized.
Remove the two phillips head screws. Carefully
remove the plastic back cover. With the instrument
operating and set to the 200mV DC range (20µF
TEST
capacitance range), apply 190mV DC (10µF) from
an accurate source.
With a small screwdriver
inserted into the semi-fixed resistor VR1 (VR2:
Capacitance), carefully turn the variable resistor
until the reading reads 190mV (10µF).
NOTE: Be sure to proceed basic calibration by DC
range first prior to capacitance.
It calls
For maximum safety, the
-32-
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