DIY Thermocouple Testing Circuit

Since I needed to test a few electronic units that read K type thermocouples it was time to create a fake thermocouple, essentially a device that could would output between ~3mV to ~30mV, or ~100ºF to ~1500ºF.



The circuit is a voltage divider  with a 150Kohm resistor and a 1Kohm precision potentiomenter (trim pot) powered by a 9 Volt Battery. To add a little character to the board we added some capacitors, an On-Off switch, an LED, a 5V voltage regulator  and the famous LM 324 Op-Amp acting like a Buffer Amplifier.

Download ZIP file (PDFs, Schematics, Etching Traces)

Some History

To "ballpark" the circuit divider we used LTSpice to plot 1K Pot Vs. Volts. Fairly good slope and descent range.

A quick schematic of the circuit was drafted with Eagle to minimize some chaos on assembly.

The board was home etched. It was an easy board to make with one side. I used a jumper wire (blue trace) to ground the Op-Amp. Doing a top and bottom etch was just too much for this project.

Once completed the board was assembled with the components. Jumper wire is visible here.

 Testing an ALCOR EGT gauge. Even with a load on the circuit the Op-Amp keeps up with it fairly well.

Of course it needed a case, so we 3D printed one just for formality 

Download ZIP file (PDFs, Schematics, Etching Traces)