Product Overview

The Epro PR6424/103-121 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of rotating machinery. It belongs to the Epro PR6424 sensor family, which is used in machinery protection and condition-monitoring systems for equipment such as steam turbines, gas turbines, compressors, pumps, and industrial fans.

The sensor operates through the eddy-current measurement principle. Instead of making physical contact with a rotating shaft, it generates an electromagnetic field and detects changes in that field as the distance between the probe and a conductive target surface changes. The resulting measurement can be used to monitor shaft displacement, vibration, axial position, eccentricity, and other important machine conditions.

The PR6424 series is designed for applications where continuous measurement of shaft movement is important to equipment reliability. In large rotating machines, changes in shaft position or vibration may indicate bearing wear, rotor imbalance, misalignment, thermal expansion, or other mechanical conditions. A properly installed eddy current sensor provides measurement information that can be processed by a compatible monitoring system.

The PR6424/103-121 has a nominal sensor head diameter of 16 mm and a supplied weight of approximately 0.2 kg. Its compact probe design allows it to be installed in suitable threaded mounting arrangements near the monitored shaft. The sensor must be used with a compatible signal converter or monitoring system configured for the PR6424 sensor family.

The exact ordering suffix is important when selecting a replacement. Cable length, connector arrangement, mounting details, and other configuration characteristics should be checked against the complete model number and the physical unit.

Technical Specifications

Note: Measurement values are published PR6424 family specifications. Confirm the exact cable, connector, mounting, and environmental configuration for the PR6424/103-121 before installation or replacement.

Function and Working Principle

The PR6424/103-121 measures the distance between the sensor tip and a conductive target using electromagnetic induction. This non-contact method is particularly useful for monitoring rotating shafts because it avoids the mechanical wear associated with contact-based measurement devices.

1. Eddy Current Measurement Principle

When the sensor is energized by a compatible signal converter, an alternating electromagnetic field is generated around the probe tip. When a conductive target, such as a steel shaft, enters this field, eddy currents are induced in the target material.

These currents influence the electromagnetic characteristics of the sensor circuit. As the distance between the probe and the target changes, the electrical response also changes.

The associated signal converter processes this response and produces a measurement signal proportional to the displacement within the specified measurement range.

2. Shaft Displacement Measurement

The sensor can measure changes in the distance between its probe tip and a rotating shaft surface. These changes provide information about shaft movement relative to the sensor mounting point.

Depending on the monitoring arrangement, the measurement can help identify:

• Radial shaft displacement.
• Axial shaft movement.
• Shaft vibration.
• Rotor eccentricity.
• Shaft position changes.
• Mechanical movement associated with operating conditions.

The sensor itself measures displacement at its installation point. Additional monitoring equipment is required to interpret the signal and generate alarms or machine-protection actions.

3. Radial and Axial Vibration Monitoring

Radial vibration describes shaft movement perpendicular to the shaft’s centerline, while axial movement occurs along the shaft’s longitudinal direction.

By installing compatible probes in appropriate positions, a machinery monitoring system can measure these movements and compare them with configured operating limits.

For example, radial probes may be mounted near a turbine bearing to monitor shaft vibration. Axial probes may be positioned to measure movement along the shaft and help identify changes in thrust-bearing conditions or rotor position.

4. Signal Sensitivity and Linearity

The PR6424 series has a typical sensitivity of 4 V/mm when used with the specified reference target material and compatible converter.

Its published linearity specification is up to ±1.5%. These characteristics allow small changes in shaft position to be represented by corresponding changes in the electrical output.

The actual measurement accuracy depends on the sensor, converter, target material, installation geometry, cable arrangement, calibration, and operating environment.

5. Non-Contact Operation

Because the probe does not need to touch the rotating shaft, it can continuously monitor shaft movement without introducing mechanical contact between the sensor and the target.

This is valuable in high-speed rotating machinery, where direct contact could cause wear, damage, or measurement instability.

The sensor must still be installed with the correct mechanical clearance and measurement gap. Incorrect positioning may result in an unsuitable output signal or operation outside the specified linear measurement range.

Role in Industrial Machinery Protection Systems

The PR6424/103-121 can serve as a measurement component in a machinery condition-monitoring system. It is typically installed near a rotating shaft and connected to a compatible signal converter and monitoring device.

Turbine Monitoring

Steam and gas turbines operate under demanding mechanical and thermal conditions. Continuous shaft-displacement measurements can help operators identify changes in rotor behavior and evaluate machinery condition.

Multiple probes may be installed at different locations to monitor radial vibration and axial displacement. Their signals can be processed by a machinery protection system to provide operating information and configured alarm functions.

Compressor Condition Monitoring

Industrial compressors contain high-speed rotating assemblies that require stable shaft positioning and vibration control.

An eddy current sensor can provide displacement information that helps maintenance personnel evaluate rotor movement, bearing behavior, and mechanical stability.

Pump Shaft Monitoring

Large process pumps may experience vibration and shaft movement caused by hydraulic conditions, bearing wear, imbalance, or misalignment.

A properly installed PR6424 sensor can provide shaft-displacement information for condition monitoring, helping maintenance teams identify abnormal changes before they develop into more serious equipment problems.

Integration with Machinery Monitoring Equipment

The sensor is not a standalone alarm or shutdown controller. It requires a compatible signal converter and monitoring platform to process its measurement signal.

The complete measuring chain typically includes:

1. Eddy current sensor probe.
2. Matching sensor cable and connection arrangement.
3. Compatible signal converter.
4. Machinery monitoring module.
5. Alarm, protection, or control system.

All components must be correctly matched and calibrated for the intended measurement range.

Industrial Applications

1. Steam Turbines

Steam turbines are used in power generation and industrial energy systems. Their rotating shafts must be monitored for vibration, displacement, and axial movement.

The PR6424 sensor family is suitable for applications involving turbine shaft measurements when the complete sensor and converter configuration meets the installation requirements.

2. Gas Turbines

Gas turbines operate at high rotational speeds and elevated temperatures. Shaft movement and vibration are important parameters for evaluating machine condition.

Non-contact displacement probes can provide continuous measurement data for compatible turbine monitoring systems.

3. Industrial Compressors

Centrifugal and other rotating compressors rely on stable rotor operation. Changes in shaft position or vibration may be associated with mechanical imbalance, bearing conditions, or operating disturbances.

Eddy current measurement provides useful information for monitoring these conditions.

4. Industrial Pumps

Large pumps used in chemical processing, power generation, water treatment, and other industries may require continuous shaft monitoring.

The sensor can be used to measure shaft displacement when the target material, shaft geometry, installation clearance, and converter configuration are suitable.

5. Industrial Fans and Blowers

Large fans and blowers contain rotating assemblies that may experience vibration caused by imbalance, mechanical wear, or mounting problems.

A compatible displacement-monitoring arrangement can help maintenance personnel observe changes in shaft movement during operation.

6. Power Generation Equipment

Power generation facilities use numerous rotating machines, including turbines, generators, compressors, and auxiliary pumps.

Non-contact shaft measurement can form part of an integrated machinery monitoring strategy, supporting equipment reliability and planned maintenance.

Installation and System Integration

Correct installation is essential for obtaining stable and repeatable measurement results. The probe position, target material, air gap, cable arrangement, and signal converter configuration all affect measurement performance.

1. Confirm the Complete Model Number

Before installation, verify that the probe is the PR6424/103-121 configuration.

Do not assume that all PR6424 probes have identical cable lengths, connectors, mounting arrangements, or mechanical dimensions. The complete ordering code should be checked against the equipment documentation.

2. Prepare the Mounting Position

The sensor should be installed in a suitable mounting location that provides a stable mechanical reference.

The probe must be positioned so that its sensing tip faces the intended target surface. The mounting arrangement should prevent unnecessary movement caused by vibration or mechanical looseness.

For threaded installations, confirm the correct thread and mounting hardware from the exact variant documentation.

3. Set the Measurement Gap

The PR6424 series has a nominal center air gap of approximately 2.7 mm under its specified reference conditions.

This is a measurement-system parameter, not a universal installation distance for every configuration. The correct gap must be established using the applicable calibration instructions and the matching converter.

An incorrect gap may place the measurement outside the intended linear range and affect the quality of the output signal.

4. Check the Shaft Material

The PR6424 series is specified for ferromagnetic steel targets, with 42CrMo4 used as the standard reference material.

Different target materials can change the electrical response of the measurement system. If the actual shaft material differs from the reference material, verify whether the sensor and converter require a different calibration arrangement.

5. Connect the Compatible Signal Converter

The sensor must be connected to a compatible converter designed for the PR6424 series.

The converter supplies the sensor excitation and processes the probe response into a usable measurement signal. Confirm the exact converter model, cable arrangement, and connector compatibility before making the connection.

Do not substitute a converter based only on physical connector similarity.

6. Route and Protect the Cable

The cable should be routed away from sources of excessive heat, mechanical damage, and electrical interference.

Avoid sharp bends, excessive pulling force, and unsupported cable sections. The exact cable length and connector configuration should be confirmed from the complete product specification.

7. Calibrate and Verify the Measurement

After installation, establish the correct measurement gap and verify the output using the approved calibration procedure.

Check the measurement response over the required operating range and confirm that the monitoring system displays the expected displacement values.

Where the sensor is used in a machinery protection system, verify alarm and trip settings through the approved commissioning process.

Compatible System Components

The PR6424/103-121 is part of a measurement chain rather than an independent monitoring system. The following components may be required depending on the installation design.

The components listed above are examples of a typical measurement arrangement. They are not necessarily included with the PR6424/103-121 sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to a broader family of eddy current sensors. Related models may share the same general measurement principle, but they should not automatically be treated as direct replacements.

Before replacing a PR6424/103-121, verify:

• Complete sensor model and ordering suffix.
• Sensor head diameter.
• Probe mounting thread and mechanical length.
• Cable length and connector type.
• Matching signal converter.
• Target material and shaft diameter.
• Static and dynamic measuring ranges.
• Sensitivity and linearity.
• Temperature and environmental limits.
• Calibration and monitoring-system settings.

A replacement sensor may physically fit but still produce an incorrect measurement if its electrical characteristics or calibration differ from the original unit.

Key Advantages

Non-Contact Measurement

The eddy current principle allows shaft displacement to be measured without direct contact. This reduces mechanical wear at the sensing interface and supports continuous monitoring.

High Sensitivity

The PR6424 series provides a typical sensitivity of 4 V/mm, allowing small changes in probe-to-target distance to be represented in the measurement output.

Shaft Vibration Monitoring

The sensor can be used in suitable monitoring arrangements to measure radial shaft vibration and other displacement-related parameters.

Compact 16 mm Probe Design

The 16 mm sensor head supports installation in suitable machinery mounting locations where space is limited.

Industrial Machinery Applications

The PR6424 family is designed for critical rotating machinery, including turbines, compressors, pumps, and fans.

Stable Measurement Characteristics

Published PR6424 series specifications include linearity of up to ±1.5% and long-term drift below 0.3% under specified conditions.

Integration with Machinery Monitoring Systems

When paired with a compatible converter, the sensor can provide measurement signals for machinery condition-monitoring and protection equipment.

Technical FAQs

1. What is the Epro PR6424/103-121?

The Epro PR6424/103-121 is a 16 mm eddy current sensor used for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm, as indicated by the product description.

3. What is the measurement principle?

It uses electromagnetic induction. The probe generates an alternating electromagnetic field, and changes in the distance to a conductive target affect the sensor response.

4. What is the typical sensitivity of the PR6424 series?

The published typical sensitivity is 4 V/mm when used with the specified reference target material and compatible converter.

5. What is the static measuring range?

The PR6424 series has a published static measuring range of ±2.0 mm.

6. What is the dynamic measuring range?

The published dynamic measurement range is 0 to 1,000 μm. The actual usable range depends on the complete measurement-chain configuration and application requirements.

7. What material should be used as the measurement target?

The PR6424 series is specified for ferromagnetic steel targets, with 42CrMo4 used as the standard reference material.

8. Does the sensor require a signal converter?

Yes. It must be connected to a compatible signal converter that provides sensor excitation and processes the measurement response.

9. What equipment can use this sensor?

Typical applications include steam turbines, gas turbines, compressors, pumps, fans, and other rotating machinery that requires shaft displacement or vibration monitoring.

10. What should be checked before replacing the PR6424/103-121?

Check the complete model number, sensor diameter, mounting arrangement, cable length, connector type, converter compatibility, target material, calibration, and monitoring-system settings. These details are essential for maintaining accurate measurements.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/103-121, verify the complete model number and compare it with the identification label on the existing probe. The PR6424 family contains different configurations, and cable length, connector type, mounting dimensions, and other details may vary.

For replacement projects, confirm that the sensor is compatible with the installed signal converter. A probe with a similar diameter may not provide the same electrical response or calibration characteristics.

Before accepting a replacement unit, inspect the sensor head, sleeve, cable, connector, and identification label. Check for mechanical damage, bent or contaminated connection points, cable cuts, and signs of improper handling.

During maintenance, inspect the mounting arrangement and ensure that the probe remains securely positioned. Verify the measurement gap and compare the output with the monitoring system’s expected values. Any changes to the sensor, converter, cable, or shaft target may require recalibration.

For critical rotating machinery, sensor replacement and commissioning should follow the equipment manufacturer’s procedures and the site’s machinery protection requirements. Accurate records of probe location, model number, calibration, and channel settings can simplify future maintenance.

Conclusion

The Epro PR6424/103-121 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in industrial rotating machinery. Its PR6424 series characteristics include typical sensitivity of 4 V/mm, linearity of up to ±1.5%, a static measurement range of ±2.0 mm, and a nominal center air gap of approximately 2.7 mm.

With a 16 mm sensor head and a supplied weight of approximately 0.2 kg, the probe can be incorporated into suitable machinery monitoring installations when paired with a compatible signal converter and monitoring system.

For maintenance and replacement applications, confirming the complete model suffix, cable and connector configuration, target material, mounting dimensions, and calibration requirements is essential to maintaining reliable measurement performance.