Ambient temperature describes surrounding air; case temperature describes a defined point on the component or mounting structure. Use the reference specified by the rating.
How it works in practice
A heatsink can run well above ambient, and the resistive element can run hotter still. Measuring the wrong point can hide an exceeded limit. Follow the manufacturer's temperature-measurement guidance, including sensor location and any emissivity considerations for infrared measurements.
Example and interpretation
A 25 °C room does not imply a resistor flange is at 25 °C during operation.
Checks before use
- Read the curve's reference
- Measure the specified point
- Account for element rise
- Apply the correct derating
Important limit
Do not substitute air temperature for case temperature without a justified model.
Related Centron RF product
50-ohm 10 W thick-film RF resistor. The linked resistor is listed as 50 ohms, 10 W and 4 GHz. Request the recommended mounting, heatsink, derating, tolerance and pulse conditions; those determine whether it is suitable for the intended circuit.
Further reading
Vishay: Resistor Technical FAQ. This background reference explains general principles; the selected Centron RF model’s datasheet governs its own ratings.
Related guides
Educational guide. Numerical examples use the stated assumptions and are not test results for a supplied unit.