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High Resolution Battery-Powered Robust Type K Thermocouple Signal Conditioning Amplifier with Cold Junction Compensation

High Resolution Battery-Powered Robust Type K Thermocouple Signal Conditioning Amplifier with Cold Junction Compensation

The circuit is used as a plug-in adapter for common digital multimeters and is completely portable. This circuit employs the LT1025 thermocouple compensator to improve accuracy over a wide range of ambient conditions and is mounted close to the thermocouple connection points for optimal thermal tracking. It precludes the need to temperature stabilize the thermocouple “cold junctions” and removes the accuracy penalty of a static room temperature correction value. The output of the LT1025 provides a 10mV/°C correction voltage for the ambient temperature difference from 0°C—normally about 250mV at room temperature. The measured probe temperature is the sum of this compensation voltage and the amplified thermocouple voltage. Simple connection of the output of the compensator to the REF input of the LTC2053 is all that is needed to add these two voltages. The only consideration with this configuration is that the correction voltage must be capable of either sourcing or sinking the feedback resistor current that flows.