A Compensated Thermocouple Amp, Ready for Arduino

When you want to measure temperature with an Arduino or other microcontrollers, there are a ton of options for sensors. Temperature chips and sensor modules abound, some with humidity sensors built-in and all with easy interfacing and an expansive supporting code library. But dip one of those sensors into, say, molten aluminum, and you’ve got a problem.

If you’re measuring something hot, you need a thermocouple. Trouble is, the signal from a thermocouple is pretty small, and needs amplification and compensation before being fed into the ADC of a typical microcontroller. Unable to find a commercial amp to meet his needs, [MonkHelios] built his own thermocouple amp for microcontrollers. The design is centered around an LTC2053 instrumentation amp, which does the job of converting the K-type thermocouple’s 40.6μV/°C output to a nicely scaled 10mV/°C range, just right for ADC consumption. He also thoughtfully included an LT1025 cold-junction compensator; thermocouple amps are referenced to 0°C, so the compensator measures the actual temperature of the cold end of the junction and scales the output accordingly. The whole amp is nicely laid out on a DIY single-sided PCB with meticulously applied solder mask — this is one of the nicest home-etched boards we’ve seen in a long time.

[Bil Herd] designed a similar thermocouple amp not too long ago himself, so you might check that out too.  Or maybe you need the basics of instrumentation amps? Our “Beyond Measure” series will get you started.

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