Helium mass spectrometer leak detectors are designed to measure the partial pressure of trace amounts of helium passing through small leaks and then display the measurement as a function of leak rate. To ensure the accuracy of the measurement, it is necessary to tune and calibrate the leak detector on a regular basis by introducing a precise flow of helium into the leak detector and comparing the output measurement with the actual flow.
This regulated flow, or leakage of tracer gas, is achieved through the use of a calibrated helium leak standard. Many of today's leak detectors have integrated or built-in calibrated leak standards. Older models of leak detectors, and current models of leak detectors that do not provide automatic calibration, may require an external calibrated leak standard to do the tune and calibration function.