The renewed airflow standard system in Japan for 5–1000 m3/h

The airflow standard system in Japan for the middle range (5–1000 m³/h) has been renewed since 2002. The constant volume tank to realize the standard was replaced to have better performance at higher pressure, although its principle is exactly the same as its predecessor. Otherwise, most hardware for the system is unchanged, however the software for controling the measurements is improved to give the capability for tele-calibration on a unique basis. The facility also has a unique time measurement system based on analog-to-digital (A/D) conversion to analyze instantaneous behaviors of flowmeters. This paper describes the outline of the renewed standard system together with some results from inter-laboratory comparison tests, in which very good consistency of the renewed system with other facilities, including its own predecessor, are shown.