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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
ZERO
n
ADJUST
FUNCTION
SWITCH
AC VOLTS--
METER
IN PARALLEL
Figure 13-1. Set-up for measuring AC voltage.
13-3. Clamp-on volt-ammeter.
terruption of service, the user may check motor
loads and starting current for fractional-horsepower
Most clamp-on volt-ammeters are designed to read
motors. Other applications include balancing
alternating current only, although some types are
polyphase systems, locating overloaded feeders,
available which will read direct current as well.
checking line voltages, trouble shooting fuse boxes
Most are provided with plug-in leads so that the
and control circuits, repairing electrical appliances,
instruments can be used as voltmeters. Some mod-
els can also be used as ohmmeters. Refer to the
and diagnosing miscellaneous operating problems.
manufacturer's instructions for operational proce-
Although the clamp-on volt-ammeter is easy to use,
dures.
care must be taken to obtain accurate readings. For
a. Application. Where a conductor is accessible at
example, be sure that the frequency of the circuit
600 volts or below, clamp-on volt-ammeters are used
under test is within the range of the instrument.
simply by clamping the instrument around insu-
Many of these instruments are calibrated at 60
lated or noninsulated conductors. Thus with no in-
Hertz. Also, take care that stray magnetic fields do
13-4
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