Inficon VGC083A - 8.3 Analog Output Correction Factors; 8.3.1 IG Analog Output Correction Factors

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The following tables and explanation contains important information regarding the
use of ionization and convection gauges on gases other than N
2
/ Air. For both
types of gauges, corrections must be applied to the analog outputs.
When using any of the analog outputs assigned to ion gauge only, use the
following steps to convert the analog output to pressure: Ion gauge analog output
correction factors for selected gases:
A) Refer to section 7 and use the related equation to convert the voltage in your
receiving instrument to pressure. This pressure value is based on nitrogen gas.
B) Apply the Gas Correction Factor for the particular gas you are using to the
pressure value obtained in step A. Use correction factors and example listed
below:
Ion Gauge Gas Correction Factors for selected gases
Gas Gas
CorrectionFactor
Gas Gas
Correction Factor
He
0.18
H
2
O
1.12
Ne
0.30
NO
1.16
D
2
0.35
Ar
1.29
H
2
0.46
CO
2
1.42
N
2
1.00
Kr
1.94
Air
1.00
SF
6
2.50
O
2
1.01
Xe
2.87
CO
1.05
Hg
3.64
ANALOG OUT 1 selected is IG LOG N-10. The gas in use is argon. Voltage output
is 4 volts. Pressure unit is Torr.
P (nitrogen) = 10
(volts - 10)
P = 10
(4 - 10)
P = 1.00 x 10
-6
Torr (based on nitrogen)
Applying the Gas Correction Factor of 1.29 for argon listed in the table above,
The correction factor must be applied to the analog output over the entire pressure
range measured by the ion gauge.
When using the IG - CG1 or IG - CG2 analog output mode (Log-Linear 0.5 - 7 V,
0.5 V/decade) for gases other than N
2
/ Air, the analog output is interpreted
differently over two different pressure ranges as discussed below:
A) Pressure range for IG from 4.00 × 10
-10
Torr to overpressure shut down value
listed in section 5.4, use the correction factors listed in section 8.3.2.1 below to
determine pressure from the voltage for selected gases (ion gauge range).
B) Pressure range of overpressure shut down value listed in section 5.4 to
1000 Torr Use the correction factors listed in section 8.3.2.2 below to determine
pressure from the voltage for selected gases (convection gauge range).
A) When using the IG - CG1 or IG - CG2 analog output mode (Log-Linear
0.5 - 7 V, 0.5 V / decade) for gases other than N
2
/ Air, use the following steps to
convert the analog output to pressure for IG when operating in the pressure range
of 4.00 × 10
-10
Torr to overpressure shut down values listed in section 5.4.
B) Refer to section 7.1 and related equation to convert the voltage in your re-
ceiving instrument to pressure. This pressure value is based on nitrogen.
8.3 Effects of Different
Gases on Analog Output
8.3.1 Ion Gauge Analog Output
Correction Factors for
Selected Gases
Example
8.3.2 IG - CG1 0.5 - 7V Analog
Output Correction
Factors for Selected
Gases
8.3.2.1 IG-CG1 0.5 - 7V Analog
Output Correction Factors
- Ion Gauge Range