73
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Measured pressure differs largely from expected value.
Possible cause
Corrective action
Sensor head cable has blown out
or insulation has failed, resulting
in leakage current.
Check insulation between electrodes of the sensor
head. Also check continuity using a circuit tester.
(See page 89
～
.)
Note: After making insulation test of the ion collector
line (coaxial contact) by a Megger, short the
portion checked with a Megger by means of a
jumper wire to discharge the charge. If the
sensor head cable is connected to the measuring
unit without taking this action, the sensor head
may fail.
If the cable is found defective, replace or repair it.
Insulation failure has occurred
between electrodes of the sensor
head, resulting in leakage
current.
Check insulation between electrodes of the sensor
head and outside wall by a Megger. (The Megger
indication must be infinite.)
(See page 86.)
If the sensor head is found defective, replace or
repair it.
Sensor head is contaminated or
sensitivity has lowered markedly.
Change the sensor head with another one and
check symptom. If there is no problem with
another sensor head, the problem is in the sensor
head now used.
Gas being measured is not
nitrogen or air. The sensitivity
setting is incorrect.
The controller and sensor head are normal. If
measurement is made using gas other than nitrogen
or air, set the sensitivity factor. (See page 28.)
The actual pressure differs from
the expected value.
Check with another vacuum gauge.
Summary of Contents for GI-M2
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