Test a Thermocouple
Thermocouples are junctions of two different metal segments. The most common application is when these different metal fragments are two wires that are twisted together at the end. Because the wires are made of different metals, they react differently to different temperatures. At any given temperature, there is an electrical potential that develops at the junction between these metals, which creates a voltage potential. Electronic thermometers measures this voltage and translate it into a temperature that can be read, usually on a digital read-out.
Instructions
1. Check the continuity of your thermocouple with an ohmmeter. A thermocouple typically is a length of two wires that are twisted together at the end. The resistance at the other end between the two ends of the wire should be minimal, less than one ohm.
2. Connect your thermocouple to your digital thermometer. Be aware of the polarity of the thermocouple wires. For a J-type thermocouple wire, the blue wire is the positive wire, and the red wire is the negative wire. Many thermocouples come attached to a plug that will plug into the digital thermometer in only the correct polarity.
3. Check your thermocouple at the temperature at which water freezes. Water freezes at 32 degrees Fahrenheit. Place the thermocouple in a bowl of water in a freezer, and the temperature readout on the digital thermometer should read 32 as the water freezes.
4. Check your thermocouple at the temperature at which water boils. Water boils at 212 degrees Fahrenheit. Place the thermocouple in a pan of water on a stove. As the water begins to boil, the temperature readout on the digital thermometer should read 212 degree Fahrenheit.
5. Record any difference in the temperature between the readout for boiling water and freezing water. This can be used as the amount of error present in your thermocouple and digital thermometer.
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