| 摘要 |
PURPOSE:To execute a measurement with a high accuracy by a simple circuit constitution, even in case a temperature sensor of a different king is replaced and used, by deriving an interval number to which an output digital value of an A/D converter belongs, when measuring a temperature, and executing an operation of a specified expression. CONSTITUTION:As for a thermometer 7, a reference integral time TS is changed by setting a kind of a temperature sensor 8 to be used, by a setting switch 11a of a conversion ratio switching circuit 11. A control circuit 20 switches a changeover switch 14, inputs an output voltage EX of a pre-amplifier 9 to an integration circuit 15 during the time Ts designated by the circuit 11, and thereafter, inputs a reference voltage -VS of the opposite polarity to an output of the amplifier 9, and outputs a gate ON signal (a) during an integral period TX of the opposite polarity of until a comparator 19 output a zero potential detection, after the switching to the reference voltage -VS. An AND gate 21 is opened by the signal (a), makes a reference clock (b) pass through, and a counter 22 counts the clock (b) and outputs it as a digital value (x). The digital value is linearized by an operating circuit 12, a temperature display value is obtained by executing an operation shown by an expression, and it is displayed. |
