SRS Labs QMS 100 Series, Руководство пользователя

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Cleaning 5-13
Technical Reference
Cleaning
The most general method of cleaning the QMS is to use the vacuum pumps to remove contaminants.
The inlet section is cleaned by installing a plug in the Ultra-Torr fitting and opening both valves. This will
cause the pumps to continually draw on these surfaces. In severe contamination cases, more aggressive
steps may be required.
Bake-out
Periodic high temperature bakeout can be used to clean the interior surfaces of the QMS system. This is
a difficult process and is only recommended in the following cases:
•
When background contamination is present in the mass spectra.
•
When the performance of the RGA is degraded due to excessive contamination.
As the RGA is used, deposits form on the ionizer parts and on the filter components. The performance
of the spectrometer is affected by the build-up of electrostatic charge on the contaminated surfaces. The
symptoms of the problem are: decreased sensitivity, decreased resolution and, in severe cases, unusual
peak shapes.
Several components limit the highest temperature that can be safely used.
· The valves contains a Viton
®
seal and are rated to 120
°
C at the valve body.
· The pressure gauge can only tolerate 85
°
C.
· The flange of the turbo pump cannot exceed 120
°
C. The bearings cannot exceed 60
°
C.
· The RGA cannot exceed 100
°
C while operating or 250
°
C if the ECU is removed.
Given these, a safe strategy is to bake the entire system at less than 80
°
C. If heating tape is used, wrap
the system, stopping at the turbo pump flange and about 1 inch before the RGA ECU flange. For more
aggressive bake-outs, careful control of temperature is required. A multipoint thermocouple monitor
(
e . g . the SR630) or temperature controllers will be necessary.
Warnings:
•
To avoid fire risk use a good quality heater with a built-in temperature limit switch.
•
To avoid overheating the components use a reliable temperature controller to regulate
the bakeout temperature.
•
Do not leave the system unattended for long periods of time.
•
To avoid damage to the electronic components detach the ECU from the probe during
bakeout.
•
Do not operate the RGA during bakeouts.
•
To avoid burns cover the heater with heavy insulation during bakeout, and do not touch
the probe until it cools down after bakeout is over.
Procedure
1. Turn off the RGA and disconnect the ECU from the probe.