GB1511845A - Gas measuring probes - Google Patents

Abstract

1511845 Solid electrolyte oxygen sensor GEORGE KENT Ltd 18 July 1975 [18 July 1974] 31940/74 Heading G1N A solid electrolyte sensor for measuring oxygen in gases comprises a tube of solid electrolyte closed at one end, electrodes, one inside and one outside the tube arranged at or near the closed end, a furnace surrounding the closed end, a reference gas supply to the interior electrode and a sealing material separating the reference gas supply from the outside of the closed end and having holes outside the furnace so that the sealing material cannot conduct reference gas to the outside electrode. The sensor is designed for measuring oxygen content of flue gases the tube of zirconia (optionally with calcia, yttria or magnesia) or of yttriathoria is maintained at about 700‹C by the furnace and a thermocouple 65. The solid electrolyte tube 1 has platinum electrodes 11 mounted on the closed end and is surrounded except at its ends by stainless steel supporting tube 13, the space between them being filled by insulating sealing material 17a, 17b. The closed end of the solid electrolyte tube is covered by a cap 19 with ports 21. Heater 27 and associated insulation 31 surrounds the electrode end of tube 1 and the heater assembly is enclosed by dust filter 33. Reference gas supply is via chamber 39. Reference gas is supplied via tube 51 to connector 55 and thence via tube 57 to the inner electrode. The gas returns between tubes 57 and 1, passes into chamber 39 then down the annular passage between tube 51 and tube 5, the tube 5 supporting the whole assembly. To prevent conduction of reference gas from chamber 39 to the outside of sensor 1 via the sealing layer 17, both stainless steel tube 13 and sealing layer 17 have apertures 15 open to flue gases in the region between chamber 39 and filter chamber 33, so that gas in sealing layer 17a is swept away and both ends of sealing layer 176 are subjected to the gas concentration to be measured.