When it comes to selecting the right thermocouple wire, it’s all about temperature and accuracy. It is vital to select a TC wire that fits within the temperature range of your application. Why? Because a wire that doesn’t fit the required temperature range will not provide accurate temperature measurement. And this could lead to system or parts damage if the elements of your application get too hot.
So how do you know if you’re picking the right thermocouple wire? There are three basic elements: calibration, conductor and insulation/jacket.
1. Calibration type: Consider the calibration type of the instrument connected to your thermocouple wire. The calibration type of the wire must match the calibration type of the instrument. In addition, the temperature to be measured can influence the calibration type as each type has a temperature range defined by ASTM E230-03 table 1. Here are some details on specific calibration types:
- Type T: is ideal for cryogenic temperatures
- Type N: is less affected by drift than Type K at higher temperatures
- Type J: provides a cost-effective calibration up to its upper temperature limit
Also reference: Can different wire calibration types be used in the same circuit?
2. Conductor: Accuracy of extension grade, standard limits or special limits. Select either a solid conductor or a stranded conductor and the desired wire gauge (AWG).
- Stranded:
- More expensive than solid
- More flexible since they are made up of smaller diameter wires
- Solid:
- Cost-effective conductor
- Easier to weld than stranded
- Not as flexible as stranded
3. Insulation and jacket:
- Temperature:
- Consider the upper and lower continuous process temperatures that will affect the wire.
- The highest temperature of the process should also be considered so that the insulation can withstand it.
- Insulation for abrasion resistance:
- This is especially challenging to select.
- For help, consult with TE Wire for a chart that shows the relative abrasion resistance of insulations.
- Corrosive gases or liquids that the insulation must bear
- Color of the conductor insulations and the jacket (if not to the ANSI standard)
Want to learn more? Download our free “Thermocouple Temperature Range and Wire Color Code Quick Reference Guide”
