Ulvac GI-M2 Instruction Manual page 77

● Pressure cannot be measured by turning ON the filament.(The [FIL]lamp on
the front panel is blinking.)
Possible cause
The emission current value is not
normal.
The filament has blown out.
Insulation between the electrodes
of the sensor head has failed.
The sensor head cable is
disconnected or insulation failure
has occurred.
The sensor head is contaminated
or its filament has worn out.
GND potential is fluctuating.
Filament protection is activated
because of high pressure.
Corrective action
Examine the real cause from other items.
Check the wiring between the filament and electrode for
continuity with a circuit tester. (See page 86.)
Change over the filament to the other. If the filament
blows out after operation above the measurable pressure
range for many hours, the sensor head interior may be
contaminated.
In this case, the emission current value may not be
normal even if the other filament is in continuity.
In this case, replace the sensor head.
Check insulation between the electrodes of the sensor
head and between the electrodes and the outside wall.
(The Megger indication should be infinite.)(See page 86.)
If insulation failure is verified, replace the sensor
head.
Check insulation between electrodes of the sensor head
using a Megger. Also check the connector at both ends
for continuity using a circuit tester. (See page 89～.)
Note: After checking the ion collector (coaxial contact) for
insulation using a Megger, short the points
measured by the Megger to discharge the charge.
If it is reconnected without discharging, the DC
amplifier of the controller may be damaged.
Replace or repair the sensor head cable.
Replace the sensor head with another one and check the
symptom again. If OK with another sensor head, the
sensor head is faulty.
Replace the sensor head.
Check control ground and ground of the sensor head
mounted position by a circuit tester or oscilloscope.
Take actions to improve the GND wiring or install the
controller or sensor head afloat.
Check pressure using another type of vacuum gauge, e.g.
Pirani gauge.
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