Product Overview

The EPRO PR6424/106-121 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the operating condition of rotating machinery. It belongs to the PR6424 sensor family developed for machinery protection and condition-monitoring applications. The sensor is used to measure shaft movement and displacement without requiring physical contact with the rotating surface.

In industrial plants, rotating equipment such as steam turbines, gas turbines, compressors, pumps, and large motors must operate within defined mechanical limits. Shaft vibration, axial movement, eccentricity, and changes in shaft position can provide important information about equipment condition. Continuous monitoring helps operators identify abnormal mechanical behavior and plan maintenance before a developing problem causes an unexpected shutdown.

The PR6424/106-121 uses eddy current measurement technology. Its 16 mm sensor head generates an electromagnetic field near a conductive target. Changes in the distance between the sensor and the target influence the sensor’s electrical response. When connected to a compatible signal converter, these changes can be converted into an electrical output representing shaft displacement or vibration.

The PR6424 family is designed for applications requiring accurate non-contact measurements on large rotating shafts. Published family specifications include a sensitivity of 4 V/mm, linearity within ±1.5%, a static measurement range of ±2.0 mm, and a dynamic measurement range of up to 1,000 μm. These characteristics make the series suitable for machinery monitoring systems where both shaft position and dynamic movement are important.

The PR6424/106-121 has a 16 mm sensor head diameter and a supplied weight of approximately 0.2 kg. Its exact cable length, connector arrangement, mounting dimensions, and configuration should be confirmed using the complete model identification and the physical product label.

Technical Specifications

Note: The performance values above describe the PR6424 family. Confirm the exact temperature range, cable length, connector, mounting arrangement, and other variant-specific details for PR6424/106-121 before installation.

Function and Working Principle

The PR6424/106-121 operates through the eddy current principle. It measures the distance between the sensor head and a conductive target, typically a ferromagnetic steel shaft. The measurement is performed without physical contact, making the sensor suitable for continuous monitoring of rotating equipment.

1. Electromagnetic Field Generation

The sensor contains a coil within its sensing head. When connected to a compatible signal converter, the coil generates a high-frequency electromagnetic field around the sensor tip.

When a conductive target approaches the sensor, eddy currents are induced in the target material. These currents influence the electromagnetic characteristics of the sensor coil.

The resulting electrical change provides the basis for determining the distance between the sensor and the target.

2. Non-Contact Displacement Measurement

The sensor measures changes in the gap between its tip and the rotating shaft. As the shaft moves toward or away from the probe, the sensor’s electrical response changes.

This measurement method allows the system to monitor shaft displacement without mechanical contact. It is particularly useful for machinery operating at high speeds, where conventional contact-based measurement methods may be unsuitable.

The PR6424 family provides a static measurement range of approximately ±2.0 mm when operated with the appropriate compatible converter and installation arrangement.

3. Shaft Vibration Monitoring

Shaft vibration is an important indicator of rotating machinery condition. Excessive vibration may be associated with imbalance, misalignment, bearing problems, looseness, or other mechanical abnormalities.

The PR6424 sensor can detect dynamic shaft movement within its specified operating range. When paired with suitable monitoring electronics, the measured signal can be used to evaluate vibration amplitude and changes in machinery behavior.

4. Position and Axial Displacement Monitoring

The sensor can also be applied to measuring shaft position and axial displacement. These measurements are important in turbines and other large rotating machines, where changes in shaft position may affect internal clearances and mechanical operating conditions.

Multiple sensors can be installed at different measurement locations to provide a more complete picture of shaft movement.

5. Signal Conversion

The sensor is part of a measurement system rather than a standalone display device. Its electrical response must be processed by a compatible signal converter or monitoring module.

The converter supplies the required excitation and converts the sensor response into a usable measurement signal. The resulting output can then be connected to a machinery protection system, condition-monitoring platform, or compatible control system.

Correct matching of the sensor, extension cable, converter, and monitoring input is essential for measurement accuracy.

Role in Industrial Machinery Protection Systems

The PR6424/106-121 can serve as a measurement component in machinery protection and condition-monitoring installations. Its main purpose is to provide shaft movement information that helps operators and maintenance personnel understand the mechanical condition of critical rotating equipment.

Turbine Monitoring

Steam and gas turbines operate under demanding mechanical and thermal conditions. Shaft vibration, axial displacement, and changes in shaft position are important parameters for evaluating turbine operation.

Eddy current sensors can be installed near suitable shaft measurement locations to monitor these mechanical variables continuously.

Compressor Condition Monitoring

Industrial compressors are often essential to production processes. Unexpected mechanical problems can affect plant availability and production efficiency.

The PR6424 family can be used in compatible compressor monitoring systems to measure shaft vibration and displacement. The collected information helps maintenance personnel identify abnormal trends and investigate possible mechanical faults.

Pump and Motor Monitoring

Large industrial pumps and motors may operate continuously for long periods. Monitoring shaft movement can help identify changes in mechanical condition that may require inspection.

A suitable sensor arrangement can provide information about shaft vibration, radial movement, and other relevant mechanical parameters.

Integration with Machinery Monitoring Equipment

The sensor can be integrated into a wider monitoring system through compatible signal-conditioning and monitoring modules. Depending on the installation, the resulting signals may be used by machinery protection equipment, diagnostic software, or plant automation systems.

The exact converter and monitoring hardware must be selected according to the sensor configuration and the measurement requirements.

Industrial Applications

1. Steam Turbines

Steam turbines are widely used in power generation and industrial energy systems. Their rotating shafts must maintain stable operating conditions under changing speed, temperature, and load.

The PR6424 sensor can support non-contact shaft vibration and displacement monitoring when installed with compatible measurement electronics.

2. Gas Turbines

Gas turbines operate at high rotational speeds and under demanding thermal conditions. Continuous machinery monitoring is important for identifying abnormal shaft movement and supporting maintenance planning.

The sensor can be used at suitable measurement points where its temperature and mechanical limits are respected.

3. Hydro Turbines and Generators

Hydroelectric generating equipment contains large rotating assemblies that require reliable mechanical monitoring. Shaft displacement and vibration measurements can help identify changes in alignment, balance, or mechanical behavior.

A properly configured eddy current monitoring system can provide continuous measurement data for these applications.

4. Industrial Compressors

Compressors used in chemical processing, petrochemical plants, gas transportation, and manufacturing facilities may require continuous vibration monitoring.

The PR6424 sensor can be incorporated into suitable compressor monitoring systems to measure shaft movement and provide information for machinery condition assessment.

5. Centrifugal Pumps

Large centrifugal pumps are used in water treatment, power generation, chemical processing, and other industrial applications.

Monitoring shaft vibration and displacement can help identify abnormal mechanical behavior and support preventive maintenance activities.

6. Industrial Fans and Blowers

Large fans and blowers may experience vibration changes caused by imbalance, misalignment, bearing wear, or mechanical looseness.

When installed in an appropriate monitoring arrangement, the sensor can provide shaft movement information for evaluating equipment condition.

Installation and System Integration

Correct installation is essential for achieving reliable measurement performance. The sensor must be positioned properly, connected to compatible electronics, and installed in accordance with the equipment manufacturer’s requirements.

1. Confirm Sensor Compatibility

Before installation, verify the complete sensor model number and the corresponding technical documentation.

Check compatibility with the signal converter, extension cable, connector, and machinery monitoring input. Do not assume that all PR6424 variants have identical cable lengths or connection arrangements.

2. Prepare the Mounting Location

The sensor should be installed at a suitable measurement location near the target shaft. The mounting arrangement must provide mechanical stability and maintain the required clearance between the sensor head and the rotating surface.

The mounting thread and dimensions should be confirmed against the exact sensor drawing. The PR6424 family uses an M18 × 1.5 mounting arrangement in published specifications, but the actual variant documentation should be checked before preparing the installation.

3. Set the Measurement Gap

The distance between the sensor tip and the target shaft is important for measurement accuracy.

Published PR6424 family documentation identifies an approximate nominal center air gap of 2.7 mm. The final installation gap must follow the applicable sensor and converter instructions.

Incorrect gap adjustment can result in inaccurate readings, reduced measurement range, or an output signal outside the intended operating region.

4. Maintain Target Material Compatibility

Eddy current sensors depend on the electrical properties of the target material. The PR6424 family specifications identify ferromagnetic steel, with 42CrMo4 as a standard reference material.

If the shaft material differs from the specified reference, its influence on measurement performance should be evaluated before commissioning.

5. Protect the Cable and Connector

The sensor cable should be routed carefully to avoid sharp bends, excessive tension, mechanical damage, and unnecessary exposure to heat.

Keep the connector clean and secure. Where electrical interference is a concern, follow the manufacturer’s grounding, shielding, and cable-routing recommendations.

6. Connect to the Compatible Signal Converter

The sensor must be connected to compatible signal-conditioning electronics. The converter provides the required operating signal and translates changes in sensor impedance into a usable output.

Verify the exact connection arrangement and cable requirements before energizing the system.

7. Commission and Verify the Measurement

After installation, confirm the initial gap, connection integrity, and output signal. Compare the measured values with the expected operating conditions and check that the monitoring system responds correctly to changes in shaft position.

Record the installation gap, sensor identification, cable configuration, converter model, and commissioning measurements for future maintenance.

Compatible System Components

The PR6424/106-121 is normally used as part of a complete eddy current measurement system. The following components may be required depending on the monitoring architecture.

The listed components describe a typical measurement arrangement. They are not necessarily supplied with the PR6424/106-121 sensor.

Alternative Models and Replacement Considerations

The PR6424 family includes multiple 16 mm sensor variants. Although they share a common measurement principle and some family-level performance characteristics, their complete configurations may differ.

Before replacing the PR6424/106-121, compare:

• Sensor head diameter.
• Complete model and suffix.
• Mounting thread and mechanical dimensions.
• Cable length and cable construction.
• Connector and extension cable arrangement.
• Sensitivity and linearity.
• Static and dynamic measurement ranges.
• Operating temperature limits.
• Compatible signal converter.
• Target material and required installation gap.

A sensor with the same 16 mm head diameter is not necessarily a direct replacement. The entire measurement chain must be checked to maintain reliable operation.

Key Advantages

Non-Contact Measurement

The eddy current principle allows the sensor to measure shaft displacement without physical contact. This makes it suitable for continuously rotating machinery.

Shaft Vibration Monitoring

The sensor can provide dynamic shaft movement information for compatible machinery monitoring systems, supporting vibration assessment and equipment condition analysis.

Position Measurement Capability

In addition to dynamic vibration measurement, the PR6424 family supports static displacement measurements within its specified range.

High Measurement Sensitivity

The published PR6424 family sensitivity of 4 V/mm supports the measurement of relatively small changes in shaft-to-probe distance.

Industrial Machinery Applications

The sensor family is designed for applications involving turbines, compressors, pumps, fans, and other large rotating machines.

Compact 16 mm Sensor Head

The 16 mm sensing head provides a practical installation format for suitable machinery measurement locations.

Integration with Monitoring Systems

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

Technical FAQs

1. What is the EPRO PR6424/106-121?

The EPRO PR6424/106-121 is a 16 mm eddy current sensor designed 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 designation and supplied product information.

3. What is the measurement principle?

It uses electromagnetic eddy current technology. The sensor generates an electromagnetic field, and changes in the distance to a conductive target influence the sensor’s electrical response.

4. What is the sensitivity of the PR6424 series?

Published PR6424 family specifications identify a sensitivity of 4 V/mm, with linearity within ±1.5%. Confirm the exact measurement-chain requirements for the installed variant.

5. What is the static measurement range?

The published PR6424 family static measurement range is approximately ±2.0 mm.

6. What is the dynamic measurement range?

The published family specification gives a dynamic measurement range of 0–1,000 μm. The actual operating range depends on the sensor installation and compatible signal converter.

7. Which machines can use this sensor?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, fans, and other rotating machinery with suitable shaft measurement locations.

8. Does the sensor require a signal converter?

Yes. The sensor is normally connected to compatible signal-conditioning electronics that supply the required excitation and convert the sensor response into a usable measurement signal.

9. What is the weight of the PR6424/106-121?

The supplied product weight is approximately 0.2 kg. Confirm whether the stated weight includes the cable, connector, protective accessories, or packaging.

10. Can another PR6424 model replace the PR6424/106-121?

Not automatically. Although PR6424 models share family-level characteristics, their cable lengths, connectors, mounting details, and other configuration features may differ. Verify the complete model number and converter compatibility before replacement.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/106-121, verify the complete model number printed on the product identification label. The PR6424 family includes several variants, and the suffix can be important when matching the sensor to an existing monitoring system.

Request clear photographs of the sensor head, mounting section, cable, connector, and identification label. Confirm the cable length and connector arrangement, particularly when the sensor is intended to replace an existing probe in a machinery protection system.

For used or surplus sensors, inspect the sensing tip, threaded sleeve, cable insulation, connector contacts, and identification markings. Check for signs of impact, corrosion, cable deformation, or previous repairs.

During maintenance, inspect the sensor mounting and cable routing for mechanical damage. Confirm that the sensor gap remains within the required range and that the signal converter produces a stable measurement output.

Keep records of the sensor model, installation location, converter configuration, initial gap, and commissioning measurements. These records can help maintenance personnel identify changes in measurement behavior and simplify future replacement work.

Conclusion

The EPRO PR6424/106-121 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement and vibration in industrial rotating machinery. Its compact sensing head and eddy current operating principle make it suitable for compatible turbine, compressor, pump, fan, and generator monitoring applications.

Published PR6424 family specifications include 4 V/mm sensitivity, ±1.5% linearity, a ±2.0 mm static measurement range, and a dynamic measurement range of 0–1,000 μm. For reliable operation, the sensor must be matched with the correct signal converter, cable, connector, and installation gap.

When sourcing or replacing this sensor, verify the complete PR6424/106-121 configuration rather than relying on the 16 mm diameter alone. Correct identification and installation help maintain measurement consistency and support reliable machinery condition monitoring.