Which device monitors the temperature of the turbine's main bearing?

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

Answer: (A)

Bearing temperature monitoring needs a sensor that gives stable, accurate readings over the range bearings experience, with a reliable and linear response. The PT100 is a platinum RTD with 100 ohms at 0°C, and its resistance increases in a predictable, nearly linear way as temperature rises. That makes it easy to convert resistance to temperature with high accuracy and repeatability, which is exactly what you want for critical bearing monitoring. In practical terms, PT100 sensors (often in a 4-wire setup) provide the precision and long-term stability that turbines require.

Thermocouples, while capable at high temperatures and fast to respond, drift with age and have nonlinear readings that necessitate more compensation. Thermistors are highly sensitive but have a limited temperature range and nonlinear behavior, making them less reliable for the steady, wide-range monitoring of bearing temps. RTD is the broader category, but PT100 is the specific device commonly used for this purpose because of its accuracy and stability.