LIQUID LEVEL DETECTOR AND LIQUID LEVEL DETECTING INSTRUMENT

摘要

PURPOSE:To enable an accurate measurement to be conducted without being affected by changes in an ambient temperature by providing a temperature compensating heat conducting plate having a thermal resistance equal to that of a liquid level detecting heat conducting plate with temperature compensating means in contact with a thermosensitive element. CONSTITUTION:This instrument is dipped in a liquid and detects the height of a liquid surface. The instrument uses a liquid level detecting PTC (positive temperature characteristic thermistor) 10 as a thermosensitive element that is self-heated and wherein an electric resistance value changes with a temperature change. A heat conducting plate 11 has a heating portion 13 in contact with the PTC 10 and a heat radiating surface 12 and thermal resistances between portions on the surface 12 and the PTC 10 are uniformed. Further, a correcting electrode 17 having the same thermal resistance as that of the plate 11 and a heat radiating surface 18 exposed to air and a temperature correcting PTC 21 having the same temperature characteristics as those of the PTC 10 in contact with the correcting electrode 17 are provided. When the electric resistance value of the PTC 21 is taken as a reference and a value corresponding to the electric resistance value of the PTC 10 is detected, changes in the electric resistance values due to changes in an ambient temperature cancel one another to enable a liquid level to be accurately detected.