- Photo acoustic infrared detectors are based on the pressure waves emitted by the SF6 molecules when illuminated by monochromatic infrared light. Special microphones detect
the acoustic signal which is directly proportional to the energy absorbed. Sensitivities down to 0,01 μl/l can be achieved which are far superior to other methods. the response time of about 15 s prevents the device being used for leak localisation.
- Electron capture detector using a ß-particle source to ionise a pumped sample. The ion current between electrodes is measured. An inert gas carrier is usually used.
this is expensive and considerably less portable than item3. Sensitivities down to 0,1 μl/l (0,1 ppmv) of SF6 in air can be achieved.
- Corona discharge cell using a high voltage (1&2 kV) applied to a point-plane electrode configuration. The discharge current is measured and used in a variety of highly portable, battery-powered units of relatively low cost. Sensitivities of below 10 μl/l can be achieved, but not with all available units.
Items 1&2 are generally used for leak tracing and quantification. item 3 suitable for either assessing whether an area contains SF6 or leak detection.