8-30
HOW TO DIAGNOSE
1600227
1660228
Normal open
(NO)
type
OFF
f$
*j/j
Current does not flow
Current flows
Normal close (NC) type
OFF
ON
a’
./I
i
/
a
t.,.;
B
a
!j
”
1
X
Current flows
Current does not flow
16A0255
3. Jumper wire
A jumper wire is used to close an open circuit. Never use
one to connect a power supply directly to a load.
4. Voltmeter
A voltmeter is used to measure the circuit voltage.
Normally, the positive (red lead) probe is applied to the point
of voltage measurement and the negative (black lead) probe
to the body ground.
5. Ohmmeter
An ohmmeter is used to check continuity or measure
resistance of a switch or coil. If the measuring range has
been changed, the zero point must be adjusted before
measurement.
CHECKING SWITCHES
In a circuit diagram, a switch is represented by a symbol and in
the idle state.
1. Normal open or normal close switch
Switches are classified into those which make the circuit
open and those which make the circuit closed when off.
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