PURPOSE: To provide immediate detection of abnormality of an equipment employing a cooling medium, by inputting an output from a temperature sensor and that from a pressure sensor into differential amplifier once passed through a temperature conversion amplifier to compare the outputs with the upper and lower limit values.

CONSTITUTION: The temperature of a cooling medium is measured with a temperature sensor and amplified with an amplifier 1 to be inputted into a differential amplifier 3. On the other hand, the pressure of cooling medium is measured with a pressure sensor while the value is translated into temperature with a temperature conversion amplifier 2 to be inputted into one of the differential amplifier 3. An output of the differential amplifier 3 is inputted into a higher- order comparator 4 and a lower-order comparator 5 and when the outputs exceed the upper and lower limit values, the output section 6 outputs an abnormal signal. This enables immediate detection of abnormality in a unit using the cooling medium. This apparatus also functions as measuring device by measuring outputs of both the amplifiers 1 and 2.