What mechanism do overload indicators on CSPs use to indicate winding temperature?

The mechanism that overload indicators on current sensing protectors (CSPs) use to indicate winding temperature is typically a metallic thermostat. A metallic thermostat operates based on the principle of thermal expansion; as temperature rises, the metallic components expand and cause a mechanical action that can trigger a switch or indicator. This allows for a reliable indication of the winding temperature, enabling protective measures to be taken if the temperature exceeds a predetermined threshold.

This type of thermal response is essential in ensuring the safety and longevity of electrical equipment by preventing overheating, which could lead to serious damage or failure. Other options such as thermal fuses are meant for one-time protection and can't provide ongoing temperature readings. Digital thermometers and analog gauges may measure temperature but do not serve the same purpose as an overload indicator specifically designed for current sensing applications. Hence, the metallic thermostat stands out as the most appropriate choice for this function within CSPs.