Downloaded from www.Manualslib.com manuals search engine GENERAL - How to Diagnose293. Jumper wire
A jumper wire is used to close an open circuit. Never
use one to connect a power supply directly to a load.
Z16602274. 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) probeto the body ground.
5. Ohmmeter
An ohmmeter is used to check continuity or measure resis-
tance of a switch or coil. If the measuring range has been
changed, the zero point must be adjusted before measure-
ment.
CHECKING SWITCHES
In a circuit diagram, a switch is represented by a symbol andin 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.
INormal open (NO) typeIOFF
/4-
1X
t
Current does not flow
16X0690
ON
1
a
ia
Current flows
16X0691
00000401
Normal close (NC) type
i===ONOFF
1
/4-
1X
Current does not flow16X0690
00000402
a
III
Current flows
16X0691
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Downloaded from www.Manualslib.com manuals search engine 30GENERAL - How to Diagnose
5432
1
18AO253
10W80800000403
Coil
Iron
Cover
Spring
Iron
core
- ContZt
21680231
(NO) type
Energized state1Normal op6
Deenergized state
--
nKilX
Current does not flow
lSXO804
!
Current flows10x0095000004042. SWITCH CONNECTION
This figure illustrates a complex switch. The continuity
between terminals at each position is as indicated in the
table below.4th stage
CHECKING RELAYS1. When current flows through the coil of a relay, its core
is magnetized to attract the iron piece, closing (ON) the
contact at the tip of the iron piece. When the coil current
is turned off, the iron piece is made to return to its original
position by a spring, opening the contact (OFF).
2.By using a relay, a heavy current can be turned on and
off by a switch of small capacity. For example, in the circuit
shown here, when the switch is turned on (closed), current
flows to the coil of the relay. Then, its contact is turned
on (closed) and the light comes on. The current flowingat this time to the switch is the relay coil current only
and is very small.3. The relays may be classified into the normal open type
and the normal close type by their contact construction.
NOTE
The deenergized state means that no current is flowing
through the coil and the energized state means that current
is flowing through the coil.
JI
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