A helium leak detectors  is used to find leaks in enclosed systems. This is done using a tracer gas, usually helium which is easily detectable because it’s light, has a very low density and is present in the atmosphere only in very small quantities (5 ppm). The resulting variation in helium concentration within the test system can then be measured and quantified. The result is a leak rate, which can be displayed and compared to other tests.

Helium leak testing can be carried out using either the vacuum or sniffer method. In the vacuum method the test object is evacuated and then filled with a search gas, in this case helium, under slight overpressure. Helium escapes through any leaks in the test object to the outside where it is detected by a sensor probe. In the sniffer method the test object is pressurized and then a sniffer probe, which is usually a mass spectrometer in sniffing mode, is used to detect the presence of helium inside the test object.

Helium Leak Detectors: Unveiling the Secrets of High-Precision Leak Detection

When using a helium leak detector it is important to calibrate the instrument with a known value. This is known as internal calibration and gives the desired confidence that a helium leak detector will correctly report the leak rate it sees. However, several factors influence accuracy beyond the control of the internal calibration process, and it is recommended that an external calibration is also performed. This technical overview explains how to do this.