| 摘要 |
1,225,692. Halogen leak detectors-ionisation gauges, automatic temperature control systems. GENERAL ELECTRIC CO. Feb. 22, 1968 [May 26, 1967], No. 8736/68. Heading G1N. [Also in Divisions G3 and H1] In a halogen leak detector the temperature of the emitter electrode is maintained constant. Construction. The detector comprises two platinum (or platinum alloy) concentric cylindrical collector and emitter electrodes 30, 31, the latter surrounding a heater coil 44 embedded in a layer 43 of emitter activating material containing an alkali metal such as rubidium. A central tubular ceramic thermistor 33 sensitive to the temperature of the emitter electrode is separated from the heater by an impervious ceramic tube 42. Temperature control system Fig. 4. A transistor amplifier 65, 67 is supplied with a regulated voltage from Zener diodes 60, 61, and variably biased by thermistor 33<SP>1</SP> to control the firing of low power SCR72 and hence SCR55 and thereby vary the number of half cycles of one polarity through heater 44. Half cyles in the other direction are supplied through diode 56, uncontrolled. Leak Detector. Fig. 1 (not shown) illustrates the use of the gas detector with a variable orifice "sniffer" probe (21). To allow the use of a constant flow vacuum pump with a variable orifice air is also sucked into the probe through a filter (11). |
