PSO (Positive Shut-Off) Calibrated Leak sources use a unique valve in which opening and closing is near instantaneous and entraps virtually no gas within the valve mechanism, assuring the user that the initial gas release is extremely close to the specified leak rate. Additionally, a low volume of entrapped gas means much longer gas reservoir lifetime and fewer refills over the course of your testing. Integrating the gas reservoir directly to the valve also limits the sources of gas leakage, further improving the lifetime of the reservoir.

Gas flow is regulated by a simple stainless steel capillary tube that has been precisely crimped. In effect, this conductance limiting orifice restricts flow to a very small, but measurable rate. Stainless steel capillary tubes are preferred over other materials because they are rugged, relatively inert, and can be reliably sealed from the reservoir without the use of elastomeric O-rings.

Calibrated leak sources are widely used for verifying the proper operation of a variety of leak-testing systems, particularly those used in industrial manufacturing of many hermetically sealed mechanical or electronic components. For example, refrigerant compressors must be leak tested in accordance with strict protocols; a calibrated leak source provides a secondary standard against which to verify that the leak-testing technology used to measure the leakage from these compressors conforms to exacting standards. Other scenarios might including the verification of carbon monoxide detector testing, or any process in which a precisely known gas concentration must be injected into a process stream.