What type of sensors are typically used to monitor the movement of a shaft inside a journal bearing?

The selection of proximity probes as the correct answer is based on their specific capability to accurately measure the movement and vibration of a shaft, particularly in applications involving journal bearings. Proximity probes operate by detecting changes in the distance between the probe and the shaft, making them ideal for monitoring shaft displacement and ensuring that the operation remains within acceptable limits. This is crucial in journal bearing systems where precise alignment and movement are vital for optimal performance and to prevent premature wear or failure.

Proximity probes provide real-time data about shaft position and can detect both lateral and axial movement. This information is valuable for condition monitoring, enabling early detection of potential issues that could escalate into more significant mechanical failures.

While the other options, such as accelerometers and velocity probes, are utilized in vibration analysis and general monitoring applications, they are less suited for directly measuring the proximity or displacement of a shaft in a journal bearing system. Accelerometers capture overall vibration levels but are not specifically designed for precise positional measurements. Thus, proximity probes remain the preferred choice in this context for ensuring the reliability and longevity of rotating machinery components.