A primary standard for the calibration of sniffer test leak devices

Abstract

Test leaks with a gas flow to atmospheric pressure are often called sniffer test leaks. They are used to calibrate leak detectors for sniffing applications. Sniffer test leaks need calibration against a standard. A primary standard for the calibration of sniffer test leaks with relatively low measurement uncertainties is described. It is assured that the measurement result is traceable to the relevant SI units and that there is a well-known and complete measurement uncertainty budget. The measurement range of the system is from 4 ? 10?11?mol?s?1 (corresponding to 10?4?Pa?l?s?1 at 23??C) to 4 ? 10?9?mol?s?1 (10?2?Pa?l?s?1 at 23??C), which is the most often needed range in industry of around 1?g loss per year of the cooling agent R134a. The temperature where the calibration can be carried out may vary from 18??C to 30??C. The flow rate of any test gas not condensing in this temperature range can be measured.