JPS55158519A - Liquid level sensor - Google Patents

Abstract

PURPOSE: To prevent both the follow-up delay of measurement and the affection by waves on the liqiud level by providing a thermistor, the electric resistance of which varies with the environment such as air or liquid, a driving gear and a measuring device by which a time of the movement of the thyristor from a fixed point to the liquid level is measured.

CONSTITUTION: A detector 25 is lowered by a motor M. While the thermistor Th is above the liquid level L, a deciding circuit 33 of the thermistor Th emits a signal "1". The signal "1" and a clock pulse from a clock circuit 31 are fed to an AND circuit 34, the number of pulses from which is counted by a counter 35. When the thermistor Th passes through the liquid level L and enters the liquid, its resistance value is changed and the deciding circuit 33 emits a signal "0". And the output signal from the AND circuit 34 becomes "0", the number of pulses counted up to that time is measured by the counter 35 and is converted into the quantity of remained liquid from the bottom of the tank to the liquid level by an arithmetic circuit 36 and the quantity of liquid is indicated by the display unit 37.

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