To obtain stabilized output voltage in a broad temperature range by using a synthetic resistance circuit network, which is constituted of only resistors containing a negative-characteristic thermistor as a temperature compensating circuit.
A water-level detector has the circuit constitution, wherein a positive- characteristic thermistor THp, a resistor R1 and a semi-fixed resistor VR are connected to a power supply E in sequence in series, a terminal voltage V1 between the positive- characteristic thermistor THp and the resistor R1 is outputted to a synthetic resistance circuit network Rx comprising resistors R2 and R3 and a negative-characteristic thermistor THn, and an output voltage V0 is outputted by a voltage dividing resistor R4. When ambient temperature T is changed, the negative-characteristic thermistor THn, by which the voltage V1 obtained by a current I1 of the positive-characteristic thermistor THp becomes R4.V1/(R4+R) (R; resistance value of negative-characteristic thermistor YHn, R4; voltage dividing resistor with negative-characteristic thermistor THn) so that the output voltage V0 becomes constant, is used. by constituting the temperature compensating circuit by the synthetic resistance circuit network including the negative-characteristic thermistor in this way, the measuring errors caused by the ambient temperature are decreased.
| WO/1994/008213 | DEVICE FOR SECURING A HOUSING |
| JPS61271422 | LEVEL DETECTOR |
| JP3344245 | LIQUID LEVEL DETECTOR AND ITS MANUFACTURE |
SHIBATA HIDEO
SAITO HIROSHI
