| 摘要 |
PROBLEM TO BE SOLVED: To obtain a rotation sensor to measure the number of revolutions of a horizontal engine utilizing changes in combustion temperature thereof through a glow plug therefor. SOLUTION: This rotary sensor comprises a glow plug part 10 and a detection circuit 20. The glow plug 10 is provided with a thermoelement 17 at the tip of a core material 11 and a heating coil 12 is connected thereto to be held within a plug body 15 by insulating materials 13 and 14. The thermoelement 17 selects chromel with thermoelectric powerαc thereof larger than the thermoelectric powerαA of the core material 11 as material. The detection circuit 20 supplies a current to the core material 11 from a battery 21 through a detecting section 22. Thus, the current is applied to be added to a thermoelectromotive force by the thermoelement 17, thereby measuring the number of revolutions from changes in output voltage attributed to changes in heat resistance of the coil 12.
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