Thermocouple Types and Mounting Methods
Thermocouples come in several types. Types K, N, and T are suitable for different temperature ranges. When using them, it is essential to firmly attach them to the DUT (device under test).
Using clips or similar methods is not suitable, as they do not provide sufficient contact and can also cool the DUT. It is recommended to glue or solder the thermocouple, as using tape can be difficult.
How to attach the thermocouple to the DUT:
Optimal thermocouple attachment.
It is important to use the minimum amount of mounting material possible. The thermocouple must be in good thermal contact with the DUT, with only a small amount of adhesive or solder between them.
It is also important that the wires are thin, especially in small components or those with multiple pins.
Selection of electrical connection points:
Thermocouples should be placed at electrically "quiet" points, preferably at terminals or points where the voltage is grounded (AC). Switching points should be avoided.
Cables should be kept away from magnetic components and switching points to prevent interference.
Ensuring proper electrical insulation:
When measuring at multiple points simultaneously, it is essential to use equipment with adequate insulation to prevent short circuits between measurement points. Optical thermal measurement with IR cameras:
Infrared cameras are used to quickly locate hot spots. However, their accuracy is limited due to the variation in emissivity between components.
Furthermore, they cannot directly measure untreated metal surfaces (e.g., by painting), which can affect the DUT temperature.
Use of IR thermometers:
IR thermometers present similar problems. Measuring shaded components is also difficult.
Additionally, the DUT surface may not accurately reflect the internal temperature. Therefore, their use is not recommended for precise final measurements.
Summary:
Both thermocouples and optical methods have advantages and limitations.
Thermocouples offer high accuracy (±1 °C), but require proper installation.
Optical methods allow for rapid identification of hot spots, but their accuracy can be affected by emissivity and measurement conditions.
