| 摘要 |
PURPOSE:To exactly measure a temperature by a simple circuit constitution, by executing a reverse integration after an input signal is integrated for a prescribed time, and constituting the circuit so as to derive a temperature, based on the time which is required for the reverse integration. CONSTITUTION:First of all, a switch S1 and S3 are closed and an integration is executed only for a prescribed time T1 by an integrator I. In such a case, a current flows to a thermistor RX, as well. Subsequently, a switch S2 is closed and a reverse integration is executed until an output V0 of an OP amplifier goes to '0'. Such a reverse integration time is counted by a clock CLK. When a resistance value of the thermistor RX is high, a counting output also goes to high, and the relation of the temperature and the counting output goes to a linear relation extending over a wide temperature range. Accordingly, the measurement can be executed exactly extending over a wide temperature range.
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