Which device monitors the temperature of the main bearing?

• A. PT 100
• B. Thermocouple
• C. Thermistor
• D. RTD

Answer: (A)

For monitoring the temperature of a main bearing, you want a sensor that is accurate, stable over time, and suitable for the typical bearing temperature range. The PT100 fits that need well because it is a platinum RTD with a 100-ohm resistance at 0°C. Its resistance changes in a nearly linear, predictable way with temperature, giving precise readings and good long-term stability, which is essential for continuous bearing monitoring and alarm systems.

Compared with a thermocouple, a PT100 provides higher accuracy and better repeatability at the moderate temperatures bearings usually run at; thermocouples can drift over time and require careful cold-junction compensation for precise readings. Thermistors, while sensitive, have a nonlinear response and a more limited usable temperature range, making them less reliable for the steady, wide-range monitoring typical in bearing systems. While RTD is the broader category and widely used, the PT100 is the standard, practical choice for bearing temperature because of its balance of accuracy, stability, and cost.