| 摘要 |
PURPOSE:To enable not only a cost reduction but also measurement from any input terminal, by connecting the current source of the input of a temp. measuring resistor to the post stage of a scanner through one point in a plurality of change-over switches. CONSTITUTION:At the input time of a temp. measuring resistor TRD1, a scanner SW2 is turned ON and all of the change-over pieces of switches S1-S4 are connected to a contact (r) and a switch S5 is closed. Whereupon, a current (i) flows through a route of RS-RTD1-SW2-I. When the input voltages of an amplifier U2 are set to E1, E2 and the resistance value of the temp. measuring resistor RTD1 is set to Tr, the output voltage E0 of the amplifier U2 is calculated by formula and amplified by an amplifier U1 to be measured through A/D conversion. When AC voltage is inputted to a thermocouple, a scanner SW1 is turned ON and the change-over pieces of the switches S1-S4 are respectively connected to a contact (t) and the switch S5 is turned OFF. As a result, the output of a thermocouple TC1 is amplified by the amplifier U1 through the switches S2, S3 and measured through A/D conversion. The output of the thermocouple TC1 is measured in a state perfectly separated from the input of the resistor RTD1.
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