INFICON T-Guard Leak Detection Sensor - Manual (Page 52)

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Operation
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5.3.4 Switching Off
You do not need to actively switch off the T-Guard™ Leak Detection Sensor. Just
switch off the power supply after usage.
5.3.5 Standby
The T-Guard™ Leak Detection Sensor will switch to standby mode automatically
after an adjustable time when it is not used. In addition to that, it is possible to switch
to standby mode manually via control unit, RS232 or digital input.
5.3.6 Helium contamination
By default, the T-Guard™ Leak Detection Sensor uses its G ROSS mode before each
measurement. Every time, when the T-Guard™recognises that the measured leak
rate exceeds five times the highest trigger value, it will stop the measurement cycle
instantly.
Due to these two facts, it is extremely unlikely that the sensor is contaminated with
helium.
If, nevertheless, the T-Guard™ should be contaminated, highly-pure nitrogen or
external air has to be pumped into the reference inlet to recover the sensor as fast
as possible.
The recovery time depends on the helium content of the air provided on the reference
inlet and the limit value of contamination. The lower the limit value of contamination
the faster the T.Guard will be ready for measurement again.
Fig. 6-13 Display of the reference value in Continuous mode.
Caution
Do not switch off the power supply when the T-Guard™ Leak Detection Sensor is
contaminated with helium. This would reduce the sensor lifetime and increase the
time of the next run-up. Please wait until the T-Guard is in Standby mode or ready
to measure (leak rate is displayed) before switching off the power supply.