A precise and robust quartz sensor based on tuning fork technology for (SF6)-gas density control

A novel sensor technology for measuring and monitoring gas density is described. The gas density sensor is self-calibrating and specifically designed to operate as a sulfur hexafluoride (SF6) monitor and control device in gas insulated high-voltage switchgears (GIS), but can also be applied for density measurement of any kind of gas. It comprises a pair of tuning forks oscillating at their resonance frequency. One oscillator is exposed to the gas to be monitored, the other one is used for comparison and temperature compensation. Exposure to gas leads to a shift in the resonance frequency proportional to the gas density. A density standard based on a combined weight and mass measurement has been performed with a precision better than 0.02%, giving proof of exact sensor calibration. The gas density sensor works with a precision batter than 0.5% over a range of 50 kg/m(3) SF6 gas density. Sensor response time is less than 50 ms. The real gas equation of Beattie and Bridgman fits the gauged values with a mean error of 0.125%. (C) 2000 Elsevier Science S.A. All rights reserved.