RESISTANCE DETECTION SENSOR

To provide a resistance detection sensor capable of suppressing a decrease in detection accuracy of an electric resistance value of a liquid.SOLUTION: A resistance detection sensor detects an electric resistance value of a liquid. The resistance detection sensor includes a pair of electrodes, a DC voltage application portion, an AC voltage application portion, and a control portion. The pair of electrodes are immersed in a liquid. The DC voltage application portion applies DC voltage having a first polarity between the pair of electrodes. The AC voltage application portion applies AC voltage between the pair of electrodes. The control portion calculates the electric resistance value of the liquid in a state where the DC voltage application portion applies the DC voltage between the pair of electrodes. The control portion controls the AC voltage application portion so as to apply the AC voltage starting from a second polarity opposite to the first polarity at a predetermined time interval between the pair of electrodes. The time period for which the AC voltage application portion applies the AC voltage between the pair of electrodes is not an integer multiple of the cycle of the AC voltage applied between the pair of electrodes.SELECTED DRAWING: Figure 1 【課題】液体の電気抵抗値の検出精度の低下を抑制可能な抵抗検出センサを提供する。【解決手段】抵抗検出センサは、液体の電気抵抗値を検出する。この抵抗検出センサは、一対の電極と、直流電圧印加部と、交流電圧印加部と、制御部とを備える。一対の電極は、液体に浸漬される。直流電圧印加部は、一対の電極間に第１極性の直流電圧を印加する。交流電圧印加部は、一対の電極間に交流電圧を印加する。制御部は、直流電圧印加部によって一対の電極間に直流電圧が印加された状態で、液体の電気抵抗値を演算する。制御部は、第１極性と逆の第２極性から始まる交流電圧を一対の電極間に所定時間間隔で印加するように交流電圧印加部を制御する。交流電圧印加部によって一対の電極間に交流電圧が印加される時間は、一対の電極間に印加される交流電圧の周期の整数倍ではない。【選択図】図１