Chapter 9 Electrical System
7. Tachometer
4LHA Serie
7-3
Measurement
of sensor
unit
characteristics
(1) Measurement of output voltage
Synchroscope
Output voltage
1.0V or higher
IV or higher
Rotation detecting sender
Measuring
conditions
Number
of teeth of
ring
gear
127
Gap
between the ring
gear
and sender
1.3mm (0.0511 in.)
Resistance
20kQ
Speed
of ring gear
500 rpm (approx. 800Hz)
Measuring
temperature
20
0
C(68
0
F)
Measuring
instrument
Synchroscope
1.3mm
'Check
the output wave pattern and number of pulses
when carrying out the output voltage measurement.
(2)
Measurement
of
internal
resistance
Measuring
conditions
Measuring
temperature
20
<,
C(68
,,
F)
Measuring
instrument
Digital tester
Digital tester
Rotation detecting sender
am
I
1
600 I
AC
100V
7-4
Fault
Does
not function well.
1) Pointer
does
not move.
2) Functions intermittently.
Diagnosis
Check
if there is
an
open-circuit cable connection at the
rear of the meter, a loose or
disconnected
terminal, or bad
continuity due to corrosion.
Disconnect
at the instrument terminals, and
measure
the
vottage between the cable terminals. (To be 10 ~ 16V)
1 Satisfactory
Remedy
Yes
Make good the connection.
No
If the input voltage is
abnormal,
check the
cause,
(e.g.
short-circuit,
disconnec-
tion, or blown fuse, etc.)
9-41
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