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Red lead
Black lead
Incorrect conection
(Pointer type)
Built-in battery
(Pointer type)
Battery
Fig. Ohmmeter principle
3. Solenoid test method
Solenoid continuity test procedure (In case of diode
incorporafed.)
Connect the black and red leads to the positive (+) and
negative (-) terminals, respectively, of a circuit tester
(pointer type). Make sure the coupler is positioned as
shown in the figure. In this state, the coil resistance can be
measured properly.
Be careful not to confuse the above connections. If
Pointer circuit tester
reverse-connected, the measuring current of the circuit
tester flows to the diode too and the coil resistance cannot
be measured correctly.
Digital circuit
tester (resistance
range)
[TIPS]
The circuit tester is battery-powered. The battery voltage
is applied across the resistor, by which a current flows and
the resistance is measured.
The built-in battery's polarities are different between the
pointer type and digital type as illustrated below. In mea-
suring the resistance of a diode-fitted coil, make connec-
tion between the positive (+) output terminal of the built-in
battery and the cathode of the diode.
(Digital type)
(Digital type)
1. Construction and principle of circuit tester
Fig. in the left shows the inside of an ohmmeter. The built-in
battery provides current through the circuit and makes the
pointer swing accordingly. Before measuring a resistance, it is
at 0 ohm
necessary to make 0-ohm adjustment. Bring the tester probes
in contact with each other for short-circuiting. By so doing, the
variable resistor R3 will be readjusted so that the pointer
should swing full-scale, and also the built-in battery's power
will be regulated. It should be noted that the measured resis-
tance and the current flowing in the coil are not in proportion
to each other. The scale is irregularly spaced. Changing the
resistance of resistor R4 allows to adjust the ohmmeter's
measuring range.
II-119
Adjusted
WSM U15-3
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