THE CHALLENGES OF MEASURING AND CALIBRATING MICRO-FLOW DEVICES and LEAK TESTING INSTRUMENTS.

摘要

The demand for micro-gas flow measurement and calibration is rapidly increasing. Increasing demands for tighter leak flow testing, micro-nozzles and MEMS flow measurements have lead to rapid improvements in the micro-gas flow measurement and calibration. Stringent environmental specifications in the automotive and refrigeration markets, as well as increasing demands for non-destructive sterility testing in the medical industry resulted in tighter leak test specifications. The tighter the requirements are, the bigger the confusion and measurement misconceptions. The paper will describe some of those issues. Newly developed sensors and standards for micro-gas flow measurements will be presented. The measurement principals of these sensors in the slip flow regime and transition / molecular flow regime will be described, including typical measurement uncertainties. These sensors are capable of measuring micro-gas flow of 0.1 microgram/min of nitrogen (approx. 1x10~(-6) std. cc/sec). The new sensors can be used for leak testing and "calibrated leak" devices certification. Calibration set up will be suggested to help reduce common errors in calibrating leak test instruments, such as helium mass spectrometers and pressure decay systems.