Patent ID: 7637148

Claim:
A liquid state detecting sensor comprising: a state detecting element comprising a heating resistor having a resistance value that changes in correspondence with a temperature thereof, the state detecting element being immersed in a liquid to be measured; an energization unit for energizing the heating resistor; a first output acquiring unit for acquiring a first output value which is outputted in correspondence with the resistance value of the heating resistor at the end of a detection time period measured from a start of the energizing of the heating resistor by the energization unit; a reference acquiring unit for acquiring a reference value which is outputted in correspondence with the resistance value of the heating resistor prior to the end of the detection time period; a first calculating unit for calculating a first calculated value using the first output value and the reference value; a state detecting unit for detecting a state of the liquid to be measured based on the first calculated value; a second output acquiring unit for acquiring a second output value corresponding to the resistance value of the heating resistor after acquiring the reference value and before acquiring the first output value; a second calculating unit for calculating a second calculated value using the second output value and the reference value; an excessive-temperature-rise determining unit for determining whether an excessive temperature rise has occurred in the state detecting element based on (i) the second calculated value, and (ii) an excessive-temperature-rise determining threshold value; and an energization terminating unit for terminating the energizing of the heating resistor by the energization unit before the end of the detection time period in response to a determination by the excessive-temperature-rise determining unit that an excessive temperature rise has occurred in the state detecting element.