| 摘要 |
PCT No. PCT/EP89/00066 Sec. 371 Date Jun. 24, 1991 Sec. 102(e) Date Jun. 24, 1991 PCT Filed Jan. 24, 1989 PCT Pub. No. WO90/08948 PCT Pub. Date Aug. 9, 1990.An optical transmitter for converting a thermocouple voltage into an optical pulse train and a low pass input filter are contained in respective spaces in a soft magnetic housing. The input filter is in lead wires from a thermocouple whose hot junction is embedded in the tip of the insulator of a spark plug of an internal combustion engine. The housing itself forms part of or is connected to the H.T. lead to the centre electrode of the spark plug. The housing is surrounded by insulating material which is itself surrounded by an earthed screening casing. The low pass filter is symmetrically constructed, both electrically and mechanically. The filter prevents interference from reaching the circuitry of the optical transmitter and the housing and the casing prevents the generation and transmission of radio interference.
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