Veeco MS40 Operation And Maintenance Manual page 123

A.V.S. Standards
Standards of the American Vacuum Society for the
Testing of Mass Spectrometer Leak Detectors
The following paragraphs are extracted, with permission of the American
Vacuum Society, from AVS Standards used in defining and testing the
operation of mass spectrometer leak detectors. They have been selected
because of their application in the testing of all VIC leak detectors.
Copies of complete AVS Standard 2.1 ("Calibration of Leak Detectors of
the Mass Spectrometer Type") and AVS Standard 2.3 ("Procedure for the
Calibration of Gas Analyzers of the Mass Spectrometry Type") are
available by writing to Vacuum Instrument Corporation.
© Copyrights 1972, 1973 by the American Vacuum Society
AVS Standard 2.1
3.1 BACKGROUND
3.1.1 General
In general, background is the total spurious indication given by the leak
detector without injected search gas. Background can originate in either
the mass spectrometer tube or the associated electric and electronic
circuitry, or both. (Frequently, the term is used to refer specifically to the
indication due to ions other than those produced from injected search gas).
3.1.2 Drift
The relatively slow change in the background. The significant parameter
is the maximum drift measured in a specified period of time.
3.1.3 Noise
The relatively rapid changes in the background. The significant parameter
is the noise measured in a specified period of time.
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