Series 360, Granville-Phillips, Stabil-Ion, Ionization, Vacuum ...

4 Preparing the Stabil-Ion System for Operation
Table 4-1 Optimum Pressure Range Settings for N 2 .
Switch Setting
Pressure Extreme
(Torr) Emission Overpressure Setpoint
H - High Range above 10 -4 0.1 mA 2x10 -2 Torr, or mbar; 2 Pa
L - Low Range below 10 -7 4 mA 5x10 -4 Torr, or mbar; 5 x 10 -2 Pa
For example, if pressures in your application will range from 1 x 10 -2 to say 5 x 10 -8 Torr, leave
the range switch on H. If much of the time the system pressure will be below approximately
1 x 10 -4 Torr, leave the switch on L. We suggest you do not change the range switch frequently
because there is a significant stabilization time to obtain steady state conditions.
NOTE: When the cathode is first turned on, or has been exposed to atmospheric pressure, it is
normal for a relatively large burst of gas to be released momentarily. Using the H range will help
prevent a nuisance shutdown from this burst.
5. When the pressure in the vicinity of IG1 is less than the overpressure setpoint listed above, as
indicated by a Convectron Gauge or another gauge, turn on IG1. See Section 4.8 on page 4-23
for automatic operation.
6. The N 2 equivalent pressure within IG1 will be displayed in the pressure units you have
specified (Torr, mbar or Pa). See Section 2.1.3 on page 2-4 to change pressure units.
7. Steps 5 and 6 also apply for IG2 if your Stabil-Ion System is equipped with the Dual Stabil-Ion
Operation module.
4.1.1 Alternate ON/OFF Gauge Control
The Stabil-Ion Gauges may be turned on and off in 4 ways:
■
Using the front panel push buttons, IG1 and IG2.
■ Remotely with the available Remote Control module, see Section 3.7 on page 3-9.
■
■
Automatically using the auto on function of the Convectron Gauge module. See Section
4.8 on page 4-23.
Using the RS-232 or IEEE 488 Computer Interface modules. See Section 4.12 on page
4-27 or Section 4.13 on page 4-31.
In addition, the Stabil-Ion Gauge will be automatically turned off by excessive pressure.
4.1.2 Gas Scale Factor Adjustment
If highly accurate measurement of pressure of gases is required, we recommend calibration for the
specific gas and system to be used. See Section 4.4 on page 4-8. The standard calibration is for N 2 .
Different gases have different ionization probabilities. If a Stabil-Ion Gauge and Controller are
calibrated for N 2 , and if argon is the predominant gas in the system, setting the scale factor at 7.75 x
10 -1 as shown in Table 4-2 on page 4-5 causes the pressure indications for N 2 to be multiplied by
0.775, thus providing correct pressure indications for argon over most of the pressure range. At
pressures above about 1 x 10 -5 Torr this method may not provide accurate pressure indications.
Series 360 Stabil-Ion December, 2001
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