990 CLD Autoline™ Leak Detector
DR
AFT 2/2/04
6-9
Minimum Detectable
Leak Rate
The magnitude of the smallest leak rate that can be unambiguously
detected by a given leak detector (in the presence of noise and
background).
Outgassing
The evolution of gas from a material in a vacuum.
Parameter Testing
The controlled circumstances under which a test is conducted.
Pressure Testing
A leak testing procedure in which tracer gas is introduced under
pressure into or around the enclosure under examination, and
detected as it is emitted from a leak.
Probe
A tube having a fine opening at one end, used for directing or
collecting a stream of tracer gas.
Probe Test
A leak lest in which the tracer gas is applied by means of a probe so
that the area covered by the tracer gas is localized. This enables
individual leaks to be located.
Rough Pump
A vacuum pump used for the initial evacuation to a
vacuum system.
Roughing
The initial evacuation of a vacuum system.
Roughing Valve
A vacuum valve placed m a roughing line to isolate the test port
and vacuum system from the roughing pump.
Sensitivity
In the case of a leak detector, the response of the detector to tracer
gas leakage (that is, scale division per unit leak rate).
Spectrometer Tube
The sensing element of a helium leak detector.
Standard Leak
1. A capillary or porous wall leak, usually in a glass or metal tube,
whose dimensions have been adjusted to give a specified leak rate
of a gas at a standard temperature with specified inlet and exit
pressures.
2. A device that permits a tracer gas to be introduced into a leak
detector or leak testing system at a known rate to facilitate tuning
and calibration of the leak detector Also known as a calibrated
leak.
Torr
Pressure unit used to replace the term millimeter of mercury
(mm or Hg). The Torr is defined as 1/760 of a standard atmosphere
or 1,013,250 dynes/cm
2
.
Turbo Molecular
Pump
A high-speed, multiple-stage, bladed compressor with an overall
compression ratio of approximately one million and exhaust
pressure in the mid vacuum range.
Turbo Molecular Drag
Pump
A high-speed, mixed technology, multiple-stage, compressor with
an overall compression ratio of approximately 1 million and an
exhaust pressure in the low vacuum range.
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