| 摘要 |
PURPOSE:To enable the adaptation of the title detection circuit to a low power measuring device by making the reference potentials of a disconnection detection signal and a measuring signal common, by changing the output level of the measuring signal at the time of the disconnection of a measuring element. CONSTITUTION:A measuring bridge circuit 30 is constituted of resistors R1-R4 each having the same resistance value and a contact 34 is connected to the non-reversal input terminal of an operational amplifier 35 while voltage based on the potential at the contact 35 of the measuring bridge circuit 30, that is, the measuring signal corresponding to the change in the resistance value of a temp. measuring resistor RTD is outputted from the operational amplifier 35. A comparing voltage forming circuit 40 consisting of a resistor 41 and a diode 42 is provided to said measuring bridge circuit 30 and comparing voltage is compared with the voltages at both terminals of the temp. measuring resistor RTD by a comparing circuit 50. At least one of comparators 51, 52 comes to a high level by this circuit when connection lines X, Y, Z of the temp. measuring resistor RTD are disconnected,a nd the detection of disconnection can be performed. |
