Eddy Current Sensors for Shaft Displacement Measurement

Built for reliable non-contact measurement, the Eddy Current Sensor is designed to accurately capture shaft displacement, shaft vibration, and rotational speed with high stability—even in harsh, contaminated environments containing oil, dust, moisture, or debris. Its robust construction and contactless operating principle make it especially suitable for continuous machinery monitoring, rotor dynamic analysis, and protective equipment systems where traditional contact sensors are impractical or unreliable.

Measurement Principle

Eddy current sensors operate based on electromagnetic induction. The sensor probe generates a high-frequency electromagnetic field at its sensing tip. When a conductive target material—such as steel or alloy shafts—enters this field, eddy currents are induced on the target surface. These eddy currents alter the impedance of the sensor coil in proportion to the distance between the probe and the target.

This change is converted into a stable analog voltage signal that directly represents displacement. Because the measurement is purely non-contact, there is no mechanical wear, and measurement accuracy is maintained even under high-speed rotation or continuous vibration.

Performance Characteristics

The eddy current sensor provides a measurement range of up to 10 mm, with a sensitivity of 0.8 V/mm and sensitivity error within ±1%. Nonlinearity is maintained below 1.5%, ensuring consistent accuracy across the usable measurement range. With a resolution of ±10 μm, the sensor is capable of detecting very small shaft movements and vibration amplitudes critical for condition monitoring.

The sensor supports a DC to 3,000 Hz (-3 dB) frequency response, making it suitable for both static displacement measurement and dynamic vibration analysis. The output signal range of 1–9 V, combined with a low output resistance of 200 Ω, ensures compatibility with most data acquisition and monitoring systems.

Environmental Robustness

Designed for industrial use, the sensor operates reliably across a temperature range of –40 °C to +80 °C, with system temperature drift limited to ±3% full scale. Powered by a 24 VDC ±10% supply, the sensor consumes a maximum current of 8 mA, supporting long-term continuous operation with minimal power demand.

The stainless-steel probe construction allows stable performance in environments where oil mist, metal particles, and vibration are present—conditions commonly found in rotating machinery and heavy industrial equipment.

Typical Applications

Eddy current sensors are widely used in:

• Shaft displacement and vibration monitoring in turbines, compressors, and motors

• Rotor dynamic analysis, including orbit and shaft centerline measurement

• Speed and phase reference measurement using keyphasor configurations

• Condition monitoring and protection systems for critical rotating assets

• Industrial test benches and machinery diagnostics

In these applications, precise real-time displacement data is essential for detecting misalignment, imbalance, bearing wear, or shaft instability.

System Integration

The eddy current sensor integrates seamlessly with Dynatronic data acquisition systems, vibration monitoring platforms, and machinery protection systems. When combined with velocity sensors, accelerometers, and pressure measurements, it provides a comprehensive view of machine health and dynamic behavior.

Reliable Non-Contact Measurement for Critical Machinery

By combining high-resolution displacement sensing, wide frequency response, and rugged non-contact design, the eddy current sensor delivers dependable performance in demanding industrial environments. It is an essential tool for engineers and maintenance teams who require accurate, continuous insight into rotating machinery behavior without compromising reliability.