Precision thermocouple signal amplifier

Posted on Jul 12, 2012

This circuit greatly expands upon the capabilities of circuit 02. A thermocouple signal is quite small, and the long thermocouple leads often induce quite a bit of noise into the system. This new circuit is far more accurate, stable, and less immune to noise. It makes use of a Linear Technologies LT1025 chip to provide CJC (Cold Junction Compensation), an LTC1098 8-bit 2-channel Analogue to Digital Converter, and an LTC1050 chopper amp.

Precision thermocouple signal amplifier
Click here to download the full size of the above Circuit.

The feedback resistors are designed to deliver 5V (full scale signal) to the ADC with a 1000 degree C. Type K signal. The 1050 is a great amplifier, delivering "rail to rail" output which makes powering the circuit simple. This circuit is far superior to the basic op-amp circuit shown above, but is still complex. The actual EGT section of the ECU has been replaced with an Analog Devices AD595 IC.

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