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2-Terminal Temperature-to-Current Thermometer Suitable for Use at the End of Long Wire Runs

2-Terminal Temperature-to-Current Thermometer Suitable for Use at the End of Long Wire Runs

By adding the LT3092 to the thermistor kit along with three 0.1% accuracy resistors and one fi nal trim, a very accurate 2-terminal temperature-to-current converter can be built. This circuit measures 700μA operating current at 0°C, dropping by 2μA every degree until 100°C, at which point the current measures 500μA. The obvious advantage to this T-to-I converter over a T-to-V converter is that current remains constant regardless of the wire length—as long as there is suffi cient voltage to meet the compliance of the LT3092 circuit while not exceeding its absolute maximum. Electronics 101: Kirchoff’s laws dictate conservation of current in the wire runs as long as there are no nodes for current to leak along the run.