Measuring probe for detecting the presence at the site of the probe of electrically conducting material in granular or liquid form

摘要

PCT No. PCT/GB91/01971 Sec. 371 Date Apr. 22, 1993 Sec. 102(e) Date Apr. 22, 1993 PCT Filed Nov. 8, 1991 PCT Pub. No. WO92/09868 PCT Pub. Date Jun. 11, 1992.A measuring probe to detect the presence of electrically conducting liquid or granular material includes a first metal electrode (4) comprising a tube (5) which is adhered to a porous, ceramic insulator (12) adhered in turn to a skirt (10) forming a second metal electrode (6). First electrode (4) is connected to a gas supply (58) supplying gas, for example nitrogen, under pressure which emerges into a space (26) in the probe and which then passes through insulator (12) to emerge from face (20) thereof. A heat resistant cable (46) has its conductor (52) brazed to cap portion (8) of second electrode (6). Cable (46) and first electrode (4) are connected into an electrical circuit (66) in which current flows when a conducting bridge of granular material simultaneously contacts both electrodes (4 and 6). Should the level of the granular material drop below second electrode (6), gas emerging from face (20) blows away any granular material trying to preserve the conducting bridge, and circuit (66) is interrupted.