Leak Calibration (Comp/Cal) 8-1
8
Chapter 8Leak Calibration (Comp/Cal)
8.1 Overview
Leak Calibration, also known as Comp /Cal, is the process by which the tester is
‘taught’ to accept a non-leaking part and reject a leaking part.
The Tester is supplied fully calibrated to measure pressure changes due to leaks.
However, in many cases, the user will require the tester to display leak rate
readings directly in flow rate units and be able to set reject limits accordingly.
Leak calibration is a two-step process: the first step is Compensation (Comp), the
second is Calibration (Cal).
• Compensation (Comp): A test is run with a non-leaking master part installed.
This is done to establish and record the small pressure decay characteristics of
the non-leaking part and the pneumatic system. In effect, the Comp test
compensates for system conditions that may appear to be leaks but are not.
• Calibration (Cal): A test is run with a non-leaking master part installed and a
calibrated Leak Master added to the circuit. This is done to quantify the
pressure loss with a known leak rate. This pressure loss is the equated to the
leak rate in sccm. In effect, the cal test calibrates the tester to know what a leak
looks like.
If you make any changes to the parameters of the test after performing a Comp/
Cal, the Comp/Cal becomes invalid. A Comp/Cal will be required if you make
changes to parameters in tests that require Comp/Cal, including the volume of
the test component. Each program needs to be calibrated individually.
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