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Instruction Manual
Effect of different gases on analog output
7.3
The following tables and explanation contains important information regarding the use of ionization and
convection gauges on gases other than N
analog outputs.
Ion gauge analog output correction factors for selected gases
7.3.1
When using the 0-9 V Log-Linear analog output for the ion gauge, use the following steps to convert the analog
output to pressure:
A) Refer to
section 6.1
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:
Gas
He
Ne
D
2
H
2
N
2
Air
O
2
CO
Example:
The gas in use is argon. Voltage output is 4 volts. Pressure unit is Torr.
(volts - 10)
P (nitrogen) = 10
(4 - 10)
P = 10
-6
P = 1.0 x 10
Torr (based on nitrogen)
Applying the Gas Correction Factor of 1.29 for argon listed in the table above,
−��
��.�� ����
P (argon) =
=
��. ���� × ����
��.����
The correction factor must be applied to the analog output over the entire pressure range measured by the ion
gauge.
InstruTech
/ Air. For both types of gauges, corrections must be applied to the
2
and use the related equation to convert the voltage in your receiving instrument to
Ion Gauge Gas Correction Factors for selected gases
Gas
Correction Factor
0.18
0.30
0.35
0.46
1.00
1.00
1.01
1.05
−��
Torr true pressure of argon gas
Gas
Gas
Correction Factor
H
O
1.12
2
NO
1.16
Ar
1.29
CO
1.42
2
Kr
1.94
SF
2.50
6
Xe
2.87
Hg
3.64
IGM402 Hornet
Page 52
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