Particle filters should include (or pressure differentialgauge display), so as to explain when should change the filter medium, when filter service life to also shall be replaced.
The precision of liquid column manometer was described. The correct use method and error correction of U tube manometer and double tube differential pressure gauge were analysed.
叙述了液柱式压力计的精度，对U形管压力计和双管差压计的正确使用方法及误差修正做了简要分析。
3
A differential pressure gauge is recommended for test no. 1 rather than a manometer for the following reasons: It utilizes minimum time to perform the test.