© Edwards Limited 2013. All rights reserved.
Page 13
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OPERATION
D048-50-880 Issue E
4.3
Emission Current
To increase the life time of the filament, the two levels of emission currents are automatically controlled by the
gauge. As the pressure goes down, the emission current changes from 0.1 mA to 1mA at 2 x 10
-5
torr (2.6 x 10
-5
mbar). As the pressure goes up, the emission current changes from 1 mA to 0.1 mA at 5 x 10
-5
torr (6.6 x 10
-5
mbar).
4.4
Degas the AIGX
CAUTION
You must degas the AIGX regularly. Failure to do so will affect the performance and reduce the lifetime of the
gauge.
During use in contaminating environments the gauge electrodes become coated in insulating layers, eventually
resulting in premature failure of the product. This can be prevented by regular use of the degas feature. Typically,
degas will be required on a weekly basis although the interval will depend on the level of contamination.
The degas operation is also recommended if measurement of low pressure are required.
During degas, the grid will be heated to high temperature, sufficient to remove absorbed gases and some
contamination.
Degas the AIGX when the pressure is below 1 x 10
-5
torr (1.3 x 10
-5
mbar). The degas is inhibited when the pressure
is above 1 x 10
-4
torr (1.3 x 10
-4
mbar). The gauge will automatically return to the normal operation mode after 3
minutes.
If you are using the AIGX with a Controller, refer to the Controller instruction manual for details of how to degas the
AIGX. Otherwise, to enable degassing of the AIGX, connect pin 6 to pin 2.
4.5
Over-pressure Protection
The gauge will automatically switch off when the measured pressure rises above 5 x 10
-2
torr (6.6 x 10
-2
mbar). If
this occurs then the signal output and LED status will indicate over-pressure trip. Refer to
.
4.6
Filament Selection
The AIGX has two filaments, 1 and 2. To select either of these filaments, use the sliding switch at the top of the
gauge. Make sure that the gauge is turned off before switching between filaments.
4.7
LED Status
The AIGX is fitted with a tri-coloured LED which can be used to monitor the status of the gauge according to the
following table:
Table 4 - LED Status
Colour
Status
Off
No power to the gauge or malfunction
Amber
Power on, gauge disabled
Green/Amber (alternating)
Emissions start-up
Green
Emission on
Green (slow flashing)
Degas on
Red (flashing)
Emission error
Red
Over-pressure trip
