| 摘要 |
PURPOSE:To detect frosting, for example, in the outdoor unit of an air conditioner without any misdecision by detecting a difference in the loss quantity of elastic wave propagation based upon whether or not there is frosting on a magnetostrictive element. CONSTITUTION:A frosting detector supplies an input signal to a coil 8 for elastic wave excitation intermittently by an input supply control means 22. At every time when the input signal is supplied, a 1st comparing means 23 compares the detection output level of a coil 9 for elastic wave detection with a set level for discriminating between the level at the time of frosting and the level at the time of nonfrosting. Further, a 2nd comparing means 24 compares respective detection output signal levels detected at constant intervals of time alternately so as to decide the increase tendency of the detection output level at the time of frosting which is not caused by the sticking of foreign matter, etc., to discriminate between the sticking state of the foreign matter and the frosting state, so that an output control means 25 outputs a defrosting signal based upon the result whose misdecision is reduced. |
