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How to Form Thermocouple Junctions

Thermocouples are temperature sensors. They are formed when two different metals are brought together to form a junction. The metals generate small voltages when subjected to different temperatures. Thermocouples are useful because of their small size, reaction time and ability to take measurements in extreme environments. Some of the materials used to make them include iron, platinum, and copper. To form a thermocouple junction, combine different metals by wrapping them around each other or soldering them together.

Things You'll Need

Paper clip
Copper wire
Bowl of boiling hot water
Bowl of ice
Digital multimeter

Instructions

- 1
  Straighten the paper clip out. Strip the insulation from the copper wire and wrap it around the paper clip. Leave the ends loose.
- 2
  Heat the thermocouple by submersing most of it into the bowl of hot water. Make sure that the ends stick out.
- 3
  Turn the multimeter on and switch it to a DC voltage setting of millivolts. Place one probe on the paper clip end and the other on the end of the copper wire. Record the voltage drop, which is the reading on the multimeter.
- 4
  Remove the thermocouple from the water, and hold it over a candle. The metal will be hot, so use an oven mitt. Again, record the voltage drop between the two metals. If necessary, use alligator clips so that the multimeter probes will not slip off. Remove the thermocouple from the heat source, and allow it to cool.
- 5
  Place the thermocouple into the bowl of ice, leaving the ends sticking out. Wait several minutes, and then record the voltage again.

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