MKS HPS 945 Series, Руководство по эксплуатации и обслуживанию

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23
Digital Pirani vacuum Sensor System
Cleaning the Pirani Sensor
Roughing pump oils and other fluids condensing or decomposing on the
heated filament can contaminate the Sensor. This changes the emissivity of
the filament, which in turn can cause the calibration to change, especially at
low pressure.
It is not advisable to clean the Sensor. Trying to clean it
may either deform or break the filament, and the deformed
filament would then cause additional error from a shift in
the Sensor's output.
Replace the Sensor if it becomes contaminated (see Accessories, p.24).
Testing the Pirani Sensor
This test is for function only. Slight Sensor damage by
contamination or rough handling can affect calibration, but the
tube may still be functional.
The most common cause of Sensor failure is a broken filament (checked
from pin 4 to pin 6). This could be due to physical abuse or sudden venting of
the Sensor to atmosphere.
Test the Sensor with an ohmmeter with less than 5 mA of current. The
resistance readings of a normal Sensor measured at atmospheric pressure
and at room temperature (20°C) are shown here.
Pin Numbers Resistance (
Ω Ω
Ω Ω Ω
)
1 to 4 39
1 to 5 114
4 to 6 31
5 to 6 114
6 to 7 62
7 to 8 345