| 摘要 |
PURPOSE:To obtain high temperature resolution regardless of whether a use temperature range is wide or narrow by varying the reference voltage of an amplifier corresponding to input thermoelectromotive force and setting the amplification output within the specific input range of an A/D converter. CONSTITUTION:The thermoelectromotive force of a thermocouple 1 is amplified by a trailing operational amplifier 3 and then converted by the A/D converter 5 into a digital value, which is supplied to a CPU 6. The CPU 6 processes the supplied digital value to control an output circuit 9 based on the arithmetic result and also controls a D/A converter 10 based on the arithmetic result to vary the reference voltage supplied to the operational amplifier 3, thereby setting the analog amplification output of the operational amplifier 3 within the specific input range of the A/D converter 5 all the time. Consequently, even when the use temperature range is wide, the temperature resolution of the whole device is held equal to that when the use temperature range is narrow.
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