| 摘要 |
PURPOSE:To make a probe small-scaled and disposable and to always detect temp. with high accuracy even when the probe is replaced, by connecting the probe containing a reference resistor to the leading end of a cable in a replaceable manner. CONSTITUTION:A correlation table of a temp. value and the digital value having predetermined relation to the temp. value is formed under the use of a reference temp.-sensitive element (thermistor) to be stored in ROM 12 as a standard table. A probe 4 contains a temp.-sensitive element (thermistor) Rth and a trimmed reference resistor Rs and the shape constant of the thermistor Rth is severely selected within a predetermined range with respect to the reference thermistor and the reference resistor Rs to be used has a resistance value constant in the ratio with the resistance value at the reference temp. of the thermistor Rth. The probe 4 is connected to the oscillation circuit 15 of a main body 1 through a cable 5 in a replaceable manner. The oscillation frequency of the oscillation circuit 15 is changed corresponding to the analogue quantity from the probe 4 and the reference table is referred to on the basis of the count value obtained by counting the oscillation frequency of the oscillation circuit 15 by a predetermined time counter 16 and the corresponding temp. value is read to be displayed on a display device 3.
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