© Arun Microelectronics Ltd 2020. All rights reserved
Page 29
Bake will be terminated automatically if a gauge fails or the
pressure exceeds the Ion Gauge overpressure limit or if the
thermocouple measuring the temperature fails or is
disconnected.
The display will show the cause of the termination, alternating
with bake duration remaining.
11.
Recorder Output
An analogue voltage representing the base-10 logarithm of collector current is available on the auxiliary connector. This is
scaled at 1 V per decade and 0 V represents 1E-13 A. The output increases by 1 V when emission is increased from 0.5 to 5
mA. The output resistance is padded to 1
kΩ
.
As the recorder output is related to collector current it has to be combined with sensitivity and emission current to derive
pressure:
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 =
10
(𝑉−13)
𝑠 × 𝐼𝑒
where
𝑉
is the recorder output voltage,
𝑠
is the sensitivity and
𝐼𝑒
is the emission current in amps.
12.
External inhibit
Operation of the Ion Gauge may be inhibited by an external contact closure, which prevents starting of the Ion Gauge by
any means. If the Ion Gauge is operating, the Ion Gauge will be switched off.
•
In Manual and Interlock Ion Gauge modes, external inhibit is latching, and once triggered requires the Function
Switch to be returned to OFF before another attempt can be made to start emission.
•
In Autostart and Ext. Inhibit mode, emission can restart automatically once the criteria for that mode are met and
the external inhibit condition is removed. In these modes, external inhibit can act as a trigger to start and stop the
Ion Gauge.
S
ee section ‘
for more information regarding Ion Gauge modes.
Summary of Contents for NGC3
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