Question regarding the unit of leakage rate for helium mass spectrometers
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http://bbs.hcbbs.com/thread-1807334-1-1.html This is the original post. The valve forum isn’t very popular – there are only two views. I’m facing a problem now: the requirement for external leakage from valves is less than 150 ppmv, yet the unit used by helium leak detection mass spectrometers is pa·m3/s. Of course, there are also models that display the value in ppm. Could you please tell me how to perform this conversion?
But ppm seems to be a dimensionless value, one part in a million; PMMV should refer to a volume ratio of one part in a million. I searched for relevant information but couldn’t find an appropriate description, and I also looked up some instructions for using mass spectrometers online with no success