Thermocouples are electrical sensors used to measure temperature. They generate an electric current and transmit it through two wires of different metals. These metals create a voltage proportional to the temperature change of the thermocouple. Then, technicians amplify this voltage and showcase it on a digital display or computer interface. Thermocouples have many uses in various fields, from industrial manufacturing to scientific research, including typical everyday applications like cooking food or bathing water. This article discusses how to wire thermocouples using easily obtainable materials found in any hardware store while offering helpful advice on wiring them accurately for precise readings.
Types of Thermocouples
There are two types of thermocouples. The standard type has two junctions that link to a measuring device via a single wire. On the other hand, the three-wire type consists of one positive and dual negative leads wherein the positive lead connects to an appliance’s hot side or heating machine, while the two negative leads connect to either end of an object being measured (or both ends if both sides require readings).
Selecting the Right Thermocouple Wire
When choosing the wire for your thermocouple, there are a few things to consider:
- Temperature Range: One of the most important things to know about a thermocouple is its temperature range. This tells you how hot or cold it can get before it breaks down and stops working. The most common types of thermocouples are made with copper (Cu) and constantan (Ni) wires. They’re designed to work in environments ranging from -200 degrees Celsius (-328 Fahrenheit) to +800 degrees Celsius (+1,472 Fahrenheit).
- Operating Environment: The operating environment is where you will use your thermocouple. This should be a well-ventilated area with no large temperature fluctuations or air currents. The surrounding area must be kept at room temperature, and humidity levels should not exceed 50%. If these conditions are not met, your thermocouple may not work properly or even break down completely.
- Chemical Exposure: It is important to know that thermocouples are sensitive to chemicals and should be protected from them. This can be done using a solvent-resistant epoxy or other protective coating, but the best way to avoid chemical exposure is simply by choosing a thermocouple that is not susceptible to those chemicals in the first place.
- Frequency of Use: The frequency of use of your thermocouple will determine which type you should buy. If it’s going to be used in a high-temperature environment, such as an exhaust system or furnace, then you’ll need a thermocouple with a higher temperature rating than if it’s just being used for testing purposes.
Step-by-Step Guide to Wiring a Thermocouple
- Determine the type of thermocouple you have.
- Check the color code on your wire.
- Strip and prepare your wire.
- Determine the length of wire required to connect your thermocouple
- Strip the ends of both wires (one on each end) so that the bare wire is exposed
- Crimp female spade terminal connectors onto both bare wires.
- Use a wire splicer connector to join the two wires together.
- Insert the prepared wires into their corresponding terminals, with bare copper touching the brass inside each terminal
- Tighten the set screw firmly against each wire to secure it in place. Do not overtighten or strip the screw!
- And there you have it! You’ve successfully wired your thermocouple.