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SO2 Measurement in SF6

Sulphur Dioxide is the most common decomposition by-product measured during SF6 gas quality analysis.  Unlike most other decomposition products, it is relatively unreactive once formed, so its concentration remains stable over time, so measurement results are more dependable as a condition assessment parameter.

Since 2012, all 973-SF6 analyzers have been produced ‘SO2 ready’.  This means that SO2 measurement can be easily added during production, or at a later time by the user. Measurement is based on a replaceable electrochemical sensor cell fitted in the gas path close to the sample inlet connection.  0…100 or 0…500 ppm ranges are available.

SO2 measurement performance is influenced by several factors that in combination can lead to measurement errors.  For this reason, measurement accuracy is specified ≤ ±2 % of the measured value.  To meet this specification, all SO2 sensors for use with the 973-SF6 are individually calibrated in gravimetrically prepared SF6/SO2 gas mixtures at three points over their specified range:

  • 100ppmv range:  0, 10, 100 ppmv
  • 500ppmv range: 0, 100, 500 ppmv