various battery, generator, and alternator voltages.
CAUTION
The common binding post is connected internally
Do not test for over 100 amperes without
to the ammeter positive (+) binding post,
using a shunt, since the meter could be
e l i m i n a t i n g the need for a jumper lead when
damaged. The large leads on the shunt are
making a load test. The load resistance may be
connected to the component being tested.
changed by the load bank control knob or removed
The small leads are connected to the meter.
from the circuit by the load bank switch. Meter B
The meter is then connected in series with
has four binding posts with the common lead on the
t h e circuit being tested. Note that the
left. Amperage is controlled by adjusting the coarse
terminals are marked external shunt.
and fine control knobs.
b. Ammenter. The ammeter is mounted on the
f. Multimeter Functions and Use.
upper left-hand side of the case (fig. 2-8) and like
the voltmeter, has terminals for connecting the
(1) Voltmeter. The voltmeter (fig. 2-8.1) is
s i m i l a r to the voltmeter portion of the LVCT.
leads. There is a common or positive (+) terminal
a n d three negative ( -- ) terminals, which are
Three meter ranges (2.5, 10, and 50 volts) are
available for use in automotive testing. Two ad-
marked 10, 50, and 100 amperes, respectively. In
ditional ranges (250) and 1,000 volts) are useful in
addition, an external shunt may be used on this
testing electronic equipment. Ranges are selected
meter to read ampere values up to 500 amperes by
by the range selector switch.
using the terminals provided for the small leads on
the shunt. Note that the meter's zero is one-third of
(2) AC voltmeter. The AC voltmeter (fig. 2-
the way up the scale. This permits reading current
power systems in the van body. Although several
flow in either direction in a circuit without
ranges are provided on the meter, only the 250-volt
changing meter leads.
range i s used for troubleshooting on the van
c. Resistance Unit. The two terminals marked
-ohm resistor or fixed resistor on the instrument
lighting and power systems.
(3) Ohmmeter. The ohmmeter (figures 2-8.3
panel provide fixed resistance for testing units in
a n d 2-8.4) is used for making resistance and
the charging circuit. The resistance unit is designed
continuity tests. T h e ohmmeter is basically a
for either 6-- or 12--volt system. Connecting test
voltmeter and internal battery connected in series,
leads between the two terminals provides -ohm
so that when the two test leads are connected
resistance. The ammeter test leads are used when
together, the voltmeter reads the battery voltage.
utilizing this resistance unit; but this unit is not in
When a conductive circuit is connected between the
a n y way connected to either the voltmeter or
test leads, the voltmeter will indicate how much
voltage is being lost (voltage drop) in the circuit. In
d. Field Rheostat Unit. The two field rheostat
the case of a length of wire, there will be little or no
t e r m i n a l s on the instrument panel provide a
voltage drop for a small coil or a resistor, there may
connection for a rheostat (or variable resistance)
be a considerable voltage drop. The amount of
located under the instrument panel. This unit is
voltage drop is directly related to the resistance (in
used to assist in charging system checks.
ohms) of the component being tested.
e. Load Bank. Meter A has six binding posts to
p r o v i d e the proper load resistance for testing
