1. The scale and pointer etc. of instrument shall comply with the technical requirements. 

2. The instrument case, glass and the base shall be assembled tightly and firmly. 

3. During checking of return-pressure before calibration, the instrument pointer scale shall move smoothly within the scale range, without beating of jamming phenomenon. 

4. When the instrument is in working position, and the measuring system is connected with the atmosphere, the instrument pointer shall be located on the zero scale mark of the scale.