MKS HPS 919 Series, Руководство по эксплуатации и обслуживанию

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Hot Cathode Ionization High Vacuum Senor System
A hot cathode ionization sensor measures pressure by the degree of
ionization of a gas, so the pressure reading depends on the type of
gas in the system. The Series 919 System is calibrated to read
pressure for air or nitrogen.
Unless calibrated otherwise, the Series 919 System displays a pressure for
other gases corresponding to the equivalent degree of ionization of nitrogen.
This pressure reading is the nitrogen equivalent pressure of the gas, and it
can be higher or lower than the true gas pressure, depending upon the
ionization characteristics of the gas at that pressure. Air calibration is
indistinguishable from nitrogen.
The Series 919 Controller can be calibrated to directly indicate pressures of
gases other than air or nitrogen. The relative sensitivity of the gas measured
is multiplied by the Sensor’s nitrogen sensitivity. The sensitivity range is
between 4 and 50 Torr
-1 .
Adjusting System Sensitivity for Another Gas
To adjust the sensitivity control for direct pressure reading of gases other
than nitrogen,
Calculate the sensitivity S with the following equation:
S = S
r
x S
sensor
where,
S
r
is the sensitivity of the gas used relative to nitrogen
S
sensor
is the sensitivity of the sensor used (e.g., 9 Torr -1 for Series 919
System's Hot Cathode Low Power Nude Sensor).
Rough values of the relative sensitivities for various gases are shown in the
table on the next page.
To determine more precisely the nitrogen equivalent pressure or the direct
pressure reading of gases, it is necessary to calibrate the Series 919 System
with the gas to be measured. This calibration requires a direct pressure
sensor such as a spinning rotor gauge to act as the calibration standard.
Using the Series 919 Hot Cathode
System with Other Gases
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