| 摘要 |
To provide a pre-heated sensor which is capable of heating the sensing element exposed to gases to a temperature of above 400 DEG C. and preferably above 500 DEG C., at which temperature the sensor will be essentially immune to lead content in the gases, an elongated heating rod is placed within a sensor structure in which a solid electrolyte tube is held in position by a first stressed compression spring, the heating rod being formed with a radially projecting flange against which a second compression spring bears, concentrically located within the first, the heating rod itself comprising a long ceramic tube, preferably formed with two longitudinal bores to accept connecting wires to a thermocouple positioned at the end of the tube to sense the temperature of the sensing tube, surrounded by a first metallic tube forming an electrical connection to one terminal of a spiral heating wire which is wrapped around a fiberglass sleeve slipped over the metallic tube, connected to a second metallic tube outside of the fiberglass sleeve which, in turn, has yet another fiberglass sleeve slipped thereover, which is split in the region of the flange, to provide a sensing element in which all components are concentrically located within each other, and held in position by an end cap and in place by compression springs to permit assembly from the region of the end cap which, upon completion of the assembly, is secured in position, and compression-stressing the springs, thereby providing reliable connection and shock and vibration resistant seating of all components while permitting simple assembly under mass production conditions. |
