| 摘要 |
PROBLEM TO BE SOLVED: To provide a liquid state detection sensor which is capable of detecting both the temperature and concentration of a liquid by one element having a heat resistor and which has the function of preventing the breakage of the element when the liquid is frozen. SOLUTION: Temperature information on a urea aqueous solution is determined on the basis of a voltage corresponding to a resistance value of the heat resistor acquired when the energization of the heat resistor is started (S1-S6). When it is below a freezing temperature, the energization is halted to prevent the heat resistor from being damaged (S7:Yes, S8). When it is above a freezing temperature (S7:NO), a voltage value corresponding to the resistance value of the heat resistor is acquired in 700 milliseconds (S10, S11). The concentration of urea of the urea aqueous solution is determined on the basis of the previously acquired voltage value and a difference valueΔV. By performing correction through the use of the previously acquired temperature information of the urea aqueous solution at this time, the concentration of urea is more accurately detected (S13-S18). COPYRIGHT: (C)2007,JPO&INPIT
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