Product Overview

The EPRO PR6424/009-021 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the condition of rotating machinery in industrial environments. It belongs to the PR6424 sensor family developed for applications requiring accurate measurement of shaft vibration, radial and axial displacement, shaft position, eccentricity, and rotational behavior.

The PR6424 series is commonly used in machinery protection and condition-monitoring systems for steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These machines often operate continuously and under demanding mechanical conditions. Monitoring shaft movement provides important information about machine stability and can help maintenance teams identify abnormal operating behavior.

Unlike contact-based measurement devices, an eddy current sensor measures the distance between its sensing tip and a conductive target without physically touching the target surface. This makes it suitable for monitoring rotating shafts where continuous mechanical contact would cause wear or interfere with measurement.

The PR6424 series uses a nominal 16 mm sensing tip and operates with a compatible signal converter. The converter processes the probe’s electrical response and produces a measurement signal for monitoring equipment or a machinery protection system.

The PR6424/009-021 is identified as a particular ordering configuration within the PR6424 family. When purchasing a replacement, the complete model number should be checked to confirm the sensor’s mechanical and electrical configuration, including cable arrangement, connector type, and compatibility with the existing converter.

Technical Specifications

Note: The measurement specifications above describe the PR6424 16 mm sensor family. Exact cable, connector, mechanical-length, and environmental details should be verified against the complete PR6424/009-021 ordering configuration.

Function and Working Principle

The PR6424/009-021 operates using the eddy current measurement principle. This technology allows the sensor to detect changes in the distance between its sensing tip and a conductive metallic target.

1. Eddy Current Measurement

The sensor contains a coil near its sensing tip. When the sensor is connected to a compatible converter, an alternating electrical signal generates an electromagnetic field around the tip.

When a conductive metal target, such as a suitable steel shaft, approaches the sensing area, the electromagnetic field induces eddy currents in the target material.

These currents influence the electrical characteristics of the sensor coil. Changes in the distance between the probe and the target produce corresponding changes in the sensor’s electrical response.

The signal converter processes these changes and converts them into an output representing the measured gap.

2. Shaft Displacement Measurement

In rotating machinery, shaft displacement can indicate changes in mechanical operating conditions. The PR6424 sensor can measure the distance between its sensing tip and the shaft surface.

By monitoring this distance continuously, the measurement system can identify changes in shaft position and movement.

This information is particularly important for large rotating machines, where shaft movement may be associated with bearing conditions, rotor imbalance, misalignment, or other mechanical changes.

3. Shaft Vibration Monitoring

The PR6424 family supports dynamic measurement of shaft movement. When installed near a rotating shaft, the sensor detects variations in the distance between the probe and the shaft surface.

The resulting signal can be used by compatible monitoring equipment to evaluate shaft vibration.

Continuous vibration monitoring helps operators understand machine behavior under different operating conditions and provides information for maintenance planning.

4. Position and Eccentricity Monitoring

The sensor can also be used to monitor shaft position and eccentricity. Eccentricity describes the deviation between the geometric center of a rotating component and its actual rotational behavior.

Monitoring these characteristics can help identify mechanical conditions that may affect machine stability.

The sensor’s performance depends on correct installation, a suitable target material, appropriate measurement gap, and a compatible signal converter.

Role in Industrial Machinery Protection Systems

The EPRO PR6424/009-021 is a sensing component rather than a complete machinery protection system. It normally operates as part of a measurement chain that includes the probe, connecting cable, signal converter, and monitoring equipment.

1. Sensor and Signal Converter

The probe detects changes in the distance to the metallic target. A compatible signal converter processes the sensor response and produces an output that can be interpreted by monitoring equipment.

The converter must match the sensor’s electrical and mechanical configuration. Using an incompatible converter may result in incorrect measurement or unreliable system operation.

2. Integration with Machinery Monitoring Equipment

The conditioned measurement signal can be connected to an appropriate machinery monitoring system. Depending on the system design, the monitoring equipment may display vibration values, shaft displacement, position, and alarm conditions.

These measurements provide operators and maintenance engineers with information about the condition of critical rotating equipment.

3. Integration with DCS and Plant Control Systems

In a typical industrial installation, machinery monitoring equipment may exchange selected operating information with a distributed control system.

The DCS can display relevant machine status and alarms alongside other process information. This allows operators to evaluate equipment behavior in relation to operating conditions such as load, speed, pressure, and temperature.

The PR6424 itself does not replace a DCS controller or machinery protection monitor. Its role is to provide the physical measurement used by the wider monitoring architecture.

Industrial Applications

The PR6424 16 mm Eddy Current Sensor is designed for non-contact monitoring of critical rotating machinery.

1. Steam Turbines

Steam turbines operate under demanding mechanical and thermal conditions. Continuous monitoring of shaft movement is important for evaluating rotor behavior and identifying abnormal vibration.

The PR6424 sensor can be installed near an appropriate shaft target to measure radial or axial displacement, depending on the measurement arrangement.

The resulting data can be used by a compatible turbine monitoring system to support machinery protection and maintenance activities.

2. Gas Turbines

Gas turbines are widely used in power generation and industrial applications. Their rotating assemblies require reliable monitoring to maintain operational stability.

Eddy current probes can provide information about shaft movement and vibration. This information helps maintenance teams evaluate machine behavior during startup, normal operation, and changing load conditions.

3. Hydro Turbines and Generators

Hydro turbines and associated generators contain large rotating components that may experience mechanical movement during operation.

Non-contact displacement sensors can monitor shaft behavior without introducing physical contact with the rotating surface.

The measurements can help identify changes in rotor alignment, vibration, and shaft position.

4. Industrial Compressors

Compressors are used in petrochemical plants, refineries, gas processing facilities, and manufacturing operations.

Because many compressors operate continuously, monitoring shaft vibration and displacement is important for identifying abnormal mechanical conditions.

The PR6424 series can be used as part of a compatible compressor monitoring arrangement.

5. Pumps

Large industrial pumps may operate under changing pressure, flow, and load conditions. Shaft vibration monitoring can provide information about mechanical performance and help identify developing equipment problems.

A correctly installed eddy current sensor can measure shaft movement without contacting the rotating component.

6. Industrial Fans

Large fans and ventilation systems may experience vibration caused by imbalance, mechanical looseness, or alignment problems.

Where the application requires shaft displacement monitoring, an eddy current sensor can provide a continuous measurement signal for compatible monitoring equipment.

Installation and System Integration

Correct installation is essential for obtaining reliable measurements from the PR6424/009-021.

1. Verify the Complete Sensor Configuration

Before installation, confirm the full model number and ordering details. PR6424 configurations can differ in sensor length, cable arrangement, armored or non-armored construction, and connector options.

The /009-021 suffix should be checked against the relevant ordering documentation rather than assumed to have the same configuration as another PR6424 model.

2. Select a Suitable Installation Position

The sensor should be mounted in a position that allows its sensing tip to face the intended metallic target.

The installation must provide sufficient clearance around the probe and prevent interference from nearby metallic structures. The sensing area should be designed according to the manufacturer’s installation recommendations.

For shaft vibration measurements, probe orientation and mounting rigidity are important. Loose mounting can introduce unwanted movement and affect measurement accuracy.

3. Set the Correct Air Gap

The PR6424 family has a nominal center air gap of approximately 2.7 mm.

The actual installation gap must be set using the applicable converter instructions and calibration procedure. The probe should not be installed by relying on visual estimation alone.

An incorrect gap may reduce the available measurement range or cause the measurement signal to operate outside its intended linear region.

4. Use Compatible Signal Conversion Equipment

The sensor must be connected to a compatible signal converter. The converter provides the required electrical interface and conditions the probe signal for use by monitoring equipment.

Before connecting the sensor, confirm the converter model, connector type, cable arrangement, and wiring requirements.

Do not assume that all PR6424 sensors and converter configurations are interchangeable.

5. Route and Protect the Cable

The sensor cable should be routed to minimize mechanical damage and electrical interference.

Avoid sharp bends, excessive pulling force, and contact with hot surfaces beyond the cable’s specified temperature limits. Maintain the minimum bending radius stated in the applicable installation documentation.

Where the installation environment requires additional mechanical protection, use an approved protective arrangement compatible with the sensor configuration.

6. Verify the Measurement Signal

After installation, inspect the probe mounting, cable connections, and converter interface. Confirm that the output responds correctly to changes in the target gap.

Where possible, compare the measured values with the commissioning baseline. Document the installed probe position, converter configuration, and initial measurement conditions for future maintenance.

Compatible System Components

The PR6424/009-021 is normally used with additional components to form a complete eddy current measurement system.

The sensor alone does not provide a complete monitoring channel. The converter, cable, and monitoring equipment must be selected as a compatible measurement system.

Alternative Models and Replacement Considerations

The PR6424 family includes multiple 16 mm sensor configurations. Some models may share similar measurement characteristics but differ in mechanical dimensions, cable length, connector type, and other ordering details.

When replacing a PR6424/009-021, compare the following:

• Sensor head diameter.
• Probe mechanical length and mounting thread.
• Cable length and construction.
• Connector type and cable termination.
• Armored or non-armored configuration.
• Signal converter compatibility.
• Measurement range and sensitivity.
• Target material and shaft dimensions.
• Environmental and temperature requirements.
• Monitoring-system input configuration.

A replacement should be approved only after confirming that its electrical and mechanical characteristics match the existing measurement channel.

Key Advantages

Non-Contact Measurement

The eddy current principle measures shaft movement without physical contact between the sensor and the rotating target. This avoids direct mechanical wear at the sensing point.

Suitable for Critical Rotating Machinery

The PR6424 series is designed for monitoring applications involving turbines, compressors, pumps, and fans.

Displacement and Vibration Monitoring

The sensor can provide information about both static shaft position and dynamic shaft movement when used with compatible signal conversion equipment.

16 mm Sensing Tip

The 16 mm sensing diameter supports installation in machinery-monitoring arrangements designed around this probe size.

Stable Measurement Characteristics

The PR6424 family provides a specified sensitivity of 4 V/mm and linearity of up to ±1.5% under the stated measurement conditions.

Integration with Machinery Monitoring Systems

When paired with a compatible converter, the sensor can supply measurement information to machinery monitoring and protection equipment.

Industrial Construction

The stainless-steel sleeve and PTFE cable construction are intended for industrial measurement applications. Actual environmental suitability must be checked against the complete sensor configuration.

Technical FAQs

1. What is the EPRO PR6424/009-021?

The PR6424/009-021 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement, vibration, position, and eccentricity in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm, consistent with the PR6424 16 mm sensor family.

3. What is the measurement principle?

It uses the eddy current principle. An electromagnetic field generated by the probe interacts with a conductive target, and changes in the probe’s electrical response are used to determine the distance between the sensor and the target.

4. What is the sensitivity of the PR6424 sensor?

The PR6424 family specifies a sensitivity of 4 V/mm, equivalent to approximately 101.6 mV/mil.

5. What is its static measurement range?

The published static measurement range is ±2.0 mm under the specified operating conditions.

6. What is the nominal air gap?

The nominal center air gap is approximately 2.7 mm. The final installation gap should be established using the compatible converter and the manufacturer’s setup procedure.

7. Does the sensor require a signal converter?

Yes. The PR6424 probe is normally used with a compatible signal converter that conditions the sensor signal for monitoring equipment.

8. What machines can use this sensor?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans.

9. What is the weight of the PR6424/009-021?

The supplied product weight is 0.2 kg. The PR6424 family specification gives an approximate reference weight of 200 grams for the sensor with a 1-meter cable and without armor. Actual weight can vary with the selected cable and mechanical configuration.

10. Can another PR6424 model replace the PR6424/009-021?

Not automatically. Other PR6424 variants may share the same sensor family and measurement principle but differ in cable, connector, probe length, and installation details. Always compare the complete ordering codes before replacement.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/009-021, verify the complete model number and confirm that the supplied probe matches the required installation configuration.

For replacement projects, compare the sensor’s cable arrangement, connector, probe length, mounting thread, and compatible signal converter with the existing measurement channel. A sensor with the same 16 mm diameter may still be unsuitable if its electrical or mechanical configuration differs.

For critical machinery, request clear product photographs and confirm the physical condition of the sensing tip, cable, connector, and threaded mounting section. Check whether the sensor is supplied individually or as part of a larger measurement assembly.

During maintenance, inspect the probe mounting for looseness, check the cable for abrasion or heat damage, and examine connector contacts for contamination or corrosion. Compare measurement values with established operating baselines and investigate unexplained changes.

For machinery protection applications, sensor replacement should be followed by appropriate gap adjustment, signal verification, and monitoring-channel testing. These steps help ensure that the replacement sensor provides reliable information to the connected machinery monitoring system.

Conclusion

The EPRO PR6424/009-021 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement, vibration, position, and eccentricity in critical rotating machinery. Its 16 mm sensing head, 4 V/mm sensitivity, and ±2.0 mm static measurement range make it part of a sensor family used in turbine, compressor, pump, and fan monitoring applications.

For industrial maintenance and procurement, the complete ordering code is essential. Confirm the cable and connector configuration, mounting dimensions, signal converter compatibility, and installation gap before selecting a replacement. When correctly installed as part of a compatible measurement system, the PR6424 sensor can provide valuable operating data for machinery condition monitoring and protection.