Paper VT-MoM6
Comparisons between Capacitance Diaphragm Gauges with Different Types of Diaphragm Materials using Force-balanced Piston Gauge

Monday, October 19, 2015, 10:00 am, Room 230B

Capacitance Diaphragm Gauge (CDG) has been one of the most accurate check or transfer standard ranging from low pressure to the high vacuum region. Nowadays, it would be practical to cover wide range of measurement in the least number of equipment possible. Knowledge on the equipment, in this case, transducer’s performance establishes not only its use but the accuracies it can maintain. CDG’s accuracies depend mostly on linearity, hysteresis and repeatability. In this paper, six (6) commercially available CDGs of two different diaphragm types, one with metal and the other with ceramic, were performance checked through comparison to a reference standard, a Force-balanced Piston Gauge (FPG), through repeated measurements ranging from 0.01 Torr to 100 Torr at different times over a month period. Performance of CDGs were observed at 10% of its full capacity to characterize its feasibility to measure at its lowest range (vacuum region), thus, its practicability to cover wide range of pressure measurement. Results showed that the maximum deviation from the standard of the CDGs with metal diaphragm is 2.24% and 1.52% and the CDGs with ceramic diaphragms 8.37% and 1.39% at low and high range respectively. Additionally, CDGs with metal diaphragm showed similar pattern of accuracy changes with pressure on both the low and high range. On the other hand, the CDGs with ceramic diaphragm showed conflicting pattern of accuracy changes with pressure on different ranges. In conclusion, no matter how the CDGs are behaving on certain ranges, these results can establish the accuracies of the CDGs tested and may further be supported by repeating same tests at a later time.