PURPOSE: To detect the state of a liquid such as a liquid level easily with high precision by utilizing ≥2 thermistors having the same positive temperature characteristics and utilizing the potential difference which is generated between the positive characteristic thermistors according to temperature.
CONSTITUTION: Positive characteristic thermistors P1 and P2 forming a detection part 3 are powered on by a power source part 1 through resistances R1 and R2 of a display part 2 to heat up. When the thermistors P1 and P2 are both dipped in a liquid O, there is no temperature difference between the both and their resistance values are nearly equal. Therefore, potentials at both terminals of a light emission diode D1 are nearly equal and there is no potential difference, so no current flows through the diode D1, which is off. If the liquid in a container 4 decreases until the thermistor P2 is exposed to air in said balanced state, the radiation state of the thermistor P2 is improved and the thermistor heats up to generate some temperature difference between both. Therefore, the diode D1 turns on owing to the current difference between the thermistors P1 and P2 and the level of the liquid is detected. Thus, the device which detects the state of the liquid easily with high precision is obtained.
KATOU TORANOSUKE
KITAZAWA SAKAE
YAMAGUCHI YOSHITERU
TOYOTA MOTOR CO LTD
| JPS5877646A | 1983-05-11 |