Product Overview

The Epro PR6424/105-121 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 industrial machinery protection and condition-monitoring systems.

The sensor operates using the eddy current measurement principle. Instead of physically contacting a rotating shaft, it is installed near a conductive target surface. Changes in the distance between the sensor tip and the target affect the electromagnetic field generated by the probe. A compatible signal converter processes these changes and produces an electrical output representing shaft displacement.

This measurement method is particularly useful for machinery where continuous contact measurement would be impractical or could introduce mechanical wear. It allows monitoring systems to observe shaft vibration, relative displacement, axial position, and other mechanical conditions without placing a moving component against the shaft.

The PR6424 family is designed for demanding rotating-equipment applications, including steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These machines often operate continuously and require reliable monitoring to help identify abnormal vibration or changes in shaft position.

The PR6424 series uses a 16 mm sensor tip and provides a sensitivity of 4 V/mm. Its published standard measurement characteristics include a static range of ±2.0 mm and a dynamic measurement range of 0 to 1,000 μm. The series also specifies a linearity error of no more than ±1.5% under its stated measurement conditions.

The PR6424/105-121 should be identified by its complete ordering code when purchasing or replacing an existing probe. Cable construction, connector arrangement, mounting dimensions, and other configuration details should be checked against the actual product label and applicable documentation.

Technical Specifications

Note: Technical performance values describe the PR6424 family. Exact cable length, connector type, probe configuration, and temperature limits for PR6424/105-121 should be confirmed against the specific unit.

Function and Working Principle

The PR6424/105-121 uses electromagnetic induction to measure the distance between the probe tip and a conductive target. The sensor itself does not need to touch the rotating shaft, making it suitable for continuous monitoring of machinery operating at high speed.

1. Eddy Current Measurement

An alternating electrical signal in the sensor coil produces an electromagnetic field around the probe tip. When a conductive metal target enters this field, eddy currents are generated on the target surface.

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

A compatible signal converter processes this response and translates it into a measurable output corresponding to the target displacement.

2. Shaft Displacement Measurement

When installed near a rotating shaft, the sensor can detect changes in the shaft’s position relative to the probe mounting point.

This information is useful for identifying radial movement, axial displacement, and changes in shaft position during operation. The monitoring system can compare measured values with configured operating limits to identify abnormal conditions.

3. Shaft Vibration Monitoring

Rotating machinery naturally produces some mechanical vibration. However, excessive vibration may indicate imbalance, misalignment, bearing deterioration, looseness, or other mechanical problems.

The PR6424 series supports dynamic displacement measurement. Its output can be used by a compatible machinery protection or condition-monitoring system to evaluate shaft vibration.

Because the sensor measures relative displacement between the shaft and its mounting reference, installation rigidity and mounting stability are important for meaningful measurements.

4. Signal Conversion

The probe is part of a measurement system rather than a standalone general-purpose analog transmitter. It normally works with a compatible EPRO signal converter.

The converter supplies the required excitation and processes the probe response. It then provides an output suitable for connection to machinery monitoring equipment.

The converter must match the probe family and measuring range. An incompatible converter can produce incorrect readings or prevent the measurement system from operating properly.

Role in Industrial Machinery Monitoring Systems

The PR6424/105-121 can be incorporated into a machinery protection system to provide continuous information about rotating equipment.

Turbine Monitoring

Steam, gas, and hydro turbines operate under demanding mechanical and thermal conditions. Shaft displacement and vibration measurements help operators evaluate mechanical behavior and identify changes that may require inspection.

A correctly installed eddy current probe can provide relative shaft movement information for the monitoring system.

Compressor Protection

Industrial compressors are used in refineries, chemical plants, gas-processing facilities, and other process industries. Changes in shaft vibration may indicate developing mechanical problems.

The PR6424 family can be used as part of a suitable compressor monitoring arrangement, provided the probe, converter, and monitoring hardware are correctly matched.

Pump Condition Monitoring

Large industrial pumps often operate continuously and may be exposed to changing hydraulic loads. Shaft movement measurements can contribute to the evaluation of pump mechanical condition.

Monitoring data can help maintenance personnel investigate abnormal vibration, bearing problems, or alignment changes.

Integration with Monitoring Equipment

A complete measurement arrangement may include:

• PR6424 eddy current probe.
• Compatible extension cable, where required by the configuration.
• EPRO signal converter.
• Machinery protection or condition-monitoring rack.
• Monitoring software and alarm interfaces.

The exact system components depend on the installed monitoring platform and the probe’s ordering configuration.

Industrial Applications

1. Steam and Gas Turbines

Turbines are critical assets in power generation and industrial processing. Their rotating shafts require continuous monitoring to help detect abnormal movement and vibration.

The PR6424 series is suitable for relevant shaft displacement measurements when installed according to the turbine monitoring design.

2. Hydro Turbines and Generators

Hydro turbines and associated generators operate with large rotating assemblies. Shaft movement measurements can help maintenance teams assess mechanical behavior and identify changes during operation.

The probe can be included in a suitable monitoring arrangement for radial or axial displacement measurement.

3. Industrial Compressors

Centrifugal and other large industrial compressors require reliable mechanical monitoring. Eddy current probes can provide non-contact shaft measurements that contribute to machinery protection.

Correct probe positioning and converter compatibility are important for accurate results.

4. Industrial Pumps

Large process pumps may operate under varying flow, pressure, and load conditions. Shaft vibration and displacement measurements can support maintenance planning and condition assessment.

5. Industrial Fans

Large fans used in power plants, steel production, and process facilities can experience imbalance, misalignment, and bearing-related vibration. Non-contact shaft measurement can contribute to monitoring these conditions.

Installation and System Integration

Proper installation is essential for accurate measurement and stable long-term operation.

1. Verify the Probe Configuration

Before installation, check the complete PR6424/105-121 ordering code and compare it with the existing probe or system documentation.

Confirm the probe’s cable arrangement, connector, mounting thread, and physical dimensions. Do not assume that all PR6424 variants have identical cable lengths or connection arrangements.

2. Select a Suitable Mounting Position

The probe should be mounted securely with its sensing tip facing the intended conductive target surface.

The mounting bracket must remain stable during machinery operation. Loose mounting hardware or vibration of the bracket can introduce measurement errors.

3. Set the Initial Air Gap

The PR6424 family specifies a nominal center air gap of approximately 2.7 mm. The actual installation gap must follow the applicable probe and converter documentation.

The gap should be set using the correct installation procedure rather than estimated visually. Incorrect positioning may reduce the available measurement range or cause the output to operate outside its intended linear region.

4. Check the Target Surface

The target should be made from an appropriate ferromagnetic material. The PR6424 family documentation uses 42CrMo4 steel as a standard reference material.

Surface condition, material properties, shaft diameter, and target geometry can affect measurement accuracy. Confirm that the actual shaft or measurement collar meets the requirements of the installed system.

5. Connect the Signal Converter

Connect the probe to a compatible EPRO converter using the specified cable and connector arrangement.

Keep sensor wiring away from high-current conductors and sources of electrical interference where required. Inspect connectors and cable insulation before commissioning.

6. Verify the Measurement Signal

After installation, check the output across the required measurement range. Confirm the initial gap, signal stability, polarity, and converter configuration.

Where the probe is used for machinery protection, verify alarm and trip settings through the approved commissioning procedure.

Compatible System Components

The PR6424/105-121 normally operates as part of a complete eddy current measurement system.

The components listed are examples of a typical measurement arrangement. They are not necessarily supplied with the sensor.

Alternative Models and Replacement Considerations

The PR6424 family contains different probe configurations. Similar sensor head diameters do not guarantee that two models are direct replacements.

Before replacing the PR6424/105-121, check:

• Complete model number and suffix.
• Sensor head diameter and mounting thread.
• Probe length and cable configuration.
• Connector type and extension cable requirements.
• Measuring range and sensitivity.
• Target material and shaft diameter.
• Operating temperature.
• Signal converter model.
• Monitoring system input and alarm configuration.

A replacement should match the complete measurement system, not simply the probe’s diameter.

Key Advantages

Non-Contact Measurement

The probe measures shaft displacement without physical contact, avoiding mechanical contact between the sensing element and the rotating target.

Continuous Machinery Monitoring

The sensor can provide displacement information for monitoring systems that operate continuously alongside critical rotating equipment.

Suitable for Critical Rotating Machinery

The PR6424 family is designed for applications involving turbines, compressors, pumps, and fans where shaft movement is an important condition-monitoring parameter.

Stable Measurement Characteristics

The series specifies a sensitivity of 4 V/mm and a linearity error of no more than ±1.5% under its stated measurement conditions.

Dynamic and Static Measurement

The sensor family supports both static shaft-position measurements and dynamic displacement measurements used for vibration monitoring.

Integration with EPRO Monitoring Systems

When paired with a compatible converter and monitoring equipment, the probe can form part of an industrial machinery protection arrangement.

Technical FAQs

1. What is the Epro PR6424/105-121?

It is a 16 mm eddy current sensor from the EPRO PR6424 family. It is designed for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the sensor head diameter?

The supplied product specification identifies a 16 mm sensor head diameter.

3. What is the measurement principle?

The probe uses electromagnetic induction. Changes in the distance between the sensor tip and a conductive target affect the eddy current response, which is processed by a compatible signal converter.

4. What is the sensitivity of the PR6424 series?

The published PR6424 family specification gives a sensitivity of 4 V/mm.

5. What is its static measuring range?

The standard PR6424 family specification gives a static measurement range of ±2.0 mm.

6. Can it measure shaft vibration?

Yes. The PR6424 family supports dynamic displacement measurement and can be used for shaft vibration monitoring when connected to a compatible converter and monitoring system.

7. Which signal converter can be used?

The CON021 is documented as compatible with PR6424 sensors. Other converter configurations should be checked against the exact probe ordering code and system documentation.

8. What material should the target shaft be made from?

The PR6424 family documentation identifies ferromagnetic steel as the target material and uses 42CrMo4 steel as a standard reference.

9. Where is this sensor commonly used?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, fans, and other critical rotating machinery.

10. What should be checked before replacing this sensor?

Verify the complete model number, sensor dimensions, cable and connector configuration, measuring range, converter compatibility, target material, and installation gap. These details are important for maintaining measurement accuracy and system compatibility.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/105-121, verify the complete model number on the sensor label. The PR6424 family includes multiple configurations, and differences in cable length, connector arrangement, and mounting details may affect replacement compatibility.

For spare-parts procurement, request clear product photographs and confirm whether the item is supplied as a probe only or with additional cables and accessories. Check the physical condition of the sensor tip, cable insulation, connector, and mounting threads.

During maintenance, inspect the probe mounting position and cable routing. Check for loose connections, damaged insulation, contamination, and changes in the initial air gap. A stable mounting arrangement is important for reliable shaft displacement measurements.

If the sensor produces an abnormal signal, investigate the probe gap, target surface, cable connection, converter compatibility, grounding, and monitoring channel configuration before concluding that the probe itself has failed.

For critical machinery, replacement and commissioning should follow the approved machinery protection procedures. Verify the measurement output and alarm response before returning the equipment to normal operation.

Conclusion

The Epro PR6424/105-121 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in industrial rotating machinery. As part of the PR6424 family, it supports monitoring applications involving turbines, compressors, pumps, fans, and other critical equipment.

Its series-level specifications include a 4 V/mm sensitivity, ±2.0 mm static measurement range, and 0–1,000 μm dynamic measurement range. When paired with a compatible signal converter and monitoring system, it can provide useful shaft movement information for machinery protection and condition monitoring.

For replacement and procurement, the complete model suffix and cable configuration should always be verified to ensure compatibility with the existing measurement system.