Product Overview

The Epro PR6424/101-021 16 mm Eddy Current Sensor is a non-contact displacement measurement sensor designed for monitoring the condition and operating behavior of rotating machinery. It belongs to the PR6424 sensor family developed for critical machinery applications, including steam turbines, gas turbines, compressors, pumps, and industrial fans.

The sensor uses electromagnetic eddy current technology to measure the distance between its sensing tip and a conductive target, typically a ferromagnetic steel shaft. Changes in the distance between the probe and the shaft produce corresponding changes in the sensor’s electrical characteristics. When connected to a compatible signal converter, these changes can be processed into measurement signals for machinery monitoring and protection systems.

The PR6424 series is designed for applications requiring reliable measurement of radial and axial shaft displacement, vibration, shaft position, eccentricity, and rotational speed-related signals. Its 16 mm sensing head provides a measurement arrangement suitable for larger rotating shafts and critical industrial equipment.

A typical PR6424 measurement chain includes the sensor probe, an appropriate extension cable where required, and a compatible signal converter. The converter conditions the probe signal and provides an output that can be used by a machinery monitoring system.

The PR6424 series has a typical sensitivity of 4 V/mm and a static measuring range of ±2.0 mm. Its dynamic measuring range is specified from 0 to 1,000 μm, with linearity of approximately ±1.5% under the specified measurement conditions.

The PR6424/101-021 should be identified by its complete model number when purchasing or replacing an existing sensor. Cable length, connector arrangement, mounting dimensions, and converter compatibility should be checked against the exact variant documentation rather than assumed from the general PR6424 series specifications.

Technical Specifications

Note: The specifications above combine the supplied product information with general PR6424 family characteristics. Confirm the exact cable, connector, mounting, and temperature specifications for PR6424/101-021 before installation.

Function and Working Principle

The PR6424/101-021 operates using the eddy current measurement principle. It measures the distance between the probe tip and a conductive target without requiring direct mechanical contact.

This measurement method is particularly useful in rotating machinery, where physical contact between the sensor and shaft would create wear and could interfere with machine operation.

1. Electromagnetic Field Generation

The sensor contains an electrical coil near its sensing tip. When the compatible measurement electronics energize the coil, an 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 surface. These currents influence the electrical characteristics of the probe coil.

2. Distance Measurement

The electrical response of the probe changes as the distance between the sensor and target changes.

When the shaft moves closer to the sensor, the probe response changes in one direction. When the shaft moves farther away, the response changes in the opposite direction.

A compatible signal converter processes this response and produces a measurement signal corresponding to the distance between the probe and the target.

3. Shaft Vibration Monitoring

During normal operation, rotating machinery experiences small movements caused by mechanical forces, imbalance, misalignment, bearing conditions, and other operating factors.

The PR6424 can measure these movements without contacting the shaft. The resulting signal can be used to monitor shaft vibration and identify changes in machine behavior.

The dynamic measurement range of the PR6424 family is specified as 0–1,000 μm, subject to the applicable system configuration and measurement conditions.

4. Shaft Position Measurement

The sensor can also be used for static displacement measurement. This is important when monitoring the position of a shaft relative to a fixed reference point.

In suitable installations, the measurement can help detect changes in axial or radial shaft position that may indicate mechanical movement, bearing wear, or changes in operating conditions.

5. Signal Conversion and Monitoring

The sensor probe is part of a measurement chain rather than a standalone machinery monitoring system. A compatible signal converter is required to condition the probe signal.

The converter provides a usable output for a machinery protection system, monitoring rack, or other compatible measurement equipment. Correct probe, cable, and converter matching is essential for accurate measurement.

Role in Industrial Machinery Monitoring Systems

The PR6424/101-021 is intended for use in machinery condition monitoring and protection arrangements. It provides non-contact displacement measurements that can help operators and maintenance personnel understand the behavior of critical rotating equipment.

Turbine Shaft Monitoring

Steam, gas, and hydro turbines operate under demanding mechanical and thermal conditions. Shaft vibration and displacement measurements are important for evaluating machine stability.

A properly installed PR6424 measurement chain can provide information about radial and axial shaft movement. These measurements may be used by a machinery monitoring system to identify abnormal changes during startup, normal operation, and shutdown.

Compressor Condition Monitoring

Industrial compressors are often critical to continuous production. Changes in shaft vibration or position may be associated with mechanical imbalance, bearing problems, misalignment, or other equipment conditions.

The PR6424 can provide non-contact shaft measurements for compatible compressor monitoring systems.

Pump Monitoring

Large industrial pumps may operate continuously in process plants, power stations, and water-treatment facilities. Shaft displacement measurements can help maintenance teams observe changes in mechanical behavior.

The sensor can be installed near a suitable shaft target when the mechanical arrangement and measurement requirements support its use.

Integration with Machinery Protection Systems

The PR6424 probe works with a compatible signal converter and monitoring equipment. The resulting measurement signals can be used by machinery protection systems to display operating values, establish alarm conditions, and support equipment shutdown logic where required.

The sensor itself does not independently provide all monitoring, alarm, or shutdown functions. These depend on the connected converter, monitoring hardware, configuration, and plant control strategy.

Industrial Applications

The PR6424 16 mm Eddy Current Sensor is designed for machinery applications where non-contact measurement of shaft displacement and vibration is required.

1. Steam Turbines

Steam turbines contain rotating assemblies that must operate within defined mechanical limits. Monitoring shaft vibration and displacement helps operators evaluate rotor behavior and identify unusual changes.

The PR6424 can be used in a compatible turbine monitoring arrangement to measure shaft movement without physical contact.

2. Gas Turbines

Gas turbines operate at high rotational speeds and under demanding temperature and load conditions. Continuous monitoring of shaft behavior is important for equipment protection and maintenance planning.

The PR6424 series is designed for critical turbomachinery applications, including gas turbine installations. Its suitability depends on the exact probe configuration, mounting arrangement, and environmental requirements.

3. Industrial Compressors

Centrifugal and other large compressors are used in chemical processing, oil and gas facilities, power generation, and manufacturing.

Shaft vibration and displacement measurements can help identify changes in compressor operating conditions. The PR6424 can provide measurement signals for compatible machinery monitoring equipment.

4. Industrial Pumps

Large pumps are widely used in water treatment, petrochemical processing, power plants, and industrial utilities.

Where shaft displacement monitoring is required, the PR6424 can be installed as part of a suitable non-contact measurement system.

5. Industrial Fans and Blowers

Large fans and blowers may experience changes in vibration due to imbalance, bearing wear, mechanical looseness, or operating conditions.

A properly configured eddy current measurement system can help monitor shaft movement and support condition-based maintenance.

6. Power Generation Equipment

Power generation facilities rely on rotating equipment that must remain mechanically stable during continuous operation.

The PR6424 can be used in appropriate monitoring systems for turbines, compressors, pumps, and other rotating machinery.

Installation and System Integration

Correct installation is essential for reliable measurement. The probe must be mounted securely, positioned correctly, and connected to compatible signal-conditioning equipment.

1. Confirm the Complete Model Number

Before installation, verify that the sensor is the required PR6424/101-021 variant.

Different PR6424 suffixes may identify different mechanical lengths, cable arrangements, connector configurations, or system compatibility details. A sensor from the same series should not automatically be treated as a direct replacement.

2. Select a Suitable Mounting Position

The sensor should be mounted at the measurement location specified by the machinery design.

For shaft vibration monitoring, the probe is normally positioned near the shaft surface with a suitable measurement gap. The mounting bracket or threaded installation arrangement must remain stable during machine operation.

The PR6424 family commonly uses a 16 mm sensing head and M18 × 1.5 mounting thread, but the exact mounting details should be confirmed for the ordered variant.

3. Set the Initial Air Gap

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

The PR6424 family specifies a nominal center air gap of approximately 2.7 mm. The actual installation gap should be established according to the applicable sensor and converter instructions.

An incorrect initial gap can cause the measurement signal to operate outside the intended linear range.

4. Verify Target Material

Eddy current sensors are sensitive to the electrical and magnetic properties of the target material.

The PR6424 specifications use ferromagnetic steel, with 42CrMo4 as the standard reference material. If the monitored shaft uses a different material or surface treatment, verify the measurement system’s calibration requirements.

5. Connect the Extension Cable and Converter

The sensor must be connected to a compatible extension cable and signal converter when required by the measurement arrangement.

Cable length, connector type, and electrical compatibility must be checked. Mixing components from different measurement systems can affect sensitivity, linearity, and measurement accuracy.

6. Protect Cable Routing

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

Observe the specified minimum bending radius and avoid pulling, crushing, or sharply bending the cable. Secure the cable so that machine vibration does not place unnecessary stress on the sensor connection.

7. Verify the Measurement Signal

After installation, check the probe and converter combination before placing the machine into normal service.

Confirm the initial gap, output signal, measurement direction, and expected operating range. Where possible, compare the measurement response with an appropriate reference or commissioning procedure.

Compatible System Components

The PR6424/101-021 is typically used as part of a complete eddy current measurement system.

A compatible converter and cable are important parts of the measurement chain. The presence of a PR6424 sensor alone does not guarantee compatibility with every machinery monitoring rack.

Alternative Models and Replacement Considerations

The PR6424 belongs to the EPRO family of eddy current sensors. Other models may be considered for different shaft sizes, measurement ranges, temperature requirements, or installation conditions.

Before replacing the PR6424/101-021, compare the following:

• Complete probe model number and suffix.
• Sensor head diameter.
• Mounting thread and mechanical length.
• Cable length and cable construction.
• Connector arrangement.
• Compatible signal converter.
• Sensitivity and linearity.
• Static and dynamic measuring ranges.
• Nominal air gap.
• Target shaft material.
• Operating temperature and environmental requirements.

A sensor with the same nominal diameter may still have different electrical or mechanical characteristics. Replacement selection should therefore be based on the complete measurement-chain requirements.

Key Advantages

Non-Contact Measurement

The eddy current principle measures shaft displacement without physical contact. This avoids direct mechanical wear between the probe and the rotating target.

Suitable for Critical Rotating Machinery

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

16 mm Sensing Head

The 16 mm sensor head is intended for measurement arrangements involving larger rotating shafts and appropriate mounting clearances.

High Measurement Sensitivity

The series provides a typical sensitivity of 4 V/mm, supporting measurement of small changes in the distance between the probe and target.

Static and Dynamic Measurement

The PR6424 can be used for static shaft position and dynamic displacement measurements within its specified operating ranges.

Industrial Environmental Design

The series uses a stainless steel sleeve and PTFE cable construction. Exact environmental limits depend on the sensor variant and installation configuration.

Integration with Machinery Monitoring Equipment

When paired with compatible extension cables and signal converters, the probe can provide measurement signals for industrial monitoring and protection systems.

Technical FAQs

1. What is the Epro PR6424/101-021?

The Epro PR6424/101-021 is a 16 mm eddy current sensor used for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the main function of this sensor?

Its main function is to measure the distance between the sensor tip and a conductive target, typically a rotating steel shaft. The measurement can be used to monitor shaft vibration, radial and axial displacement, position, and eccentricity.

3. What is the sensor head diameter?

The sensor head diameter is 16 mm, as specified in the supplied product description.

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

The typical sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil, under the specified measurement conditions.

5. What is the static measurement range?

The PR6424 family has a static measurement range of ±2.0 mm.

6. What is the dynamic measurement range?

The typical dynamic measurement range is 0–1,000 μm. The actual usable range depends on the complete measurement system and installation conditions.

7. What type of material can the sensor measure?

The PR6424 is specified for conductive ferromagnetic targets. Its standard reference material is 42CrMo4 steel. Different target materials may require specific calibration or verification.

8. Does the sensor work without a signal converter?

The PR6424 probe is normally used with a compatible signal converter. The converter processes the probe’s electrical response and provides a usable measurement output for monitoring equipment.

9. What is the weight of the PR6424/101-021?

The supplied product weight is 0.2 kg. The PR6424 specifications list approximately 200 grams for the sensor with a 1-meter cable without armor. The exact weight may vary with cable length and construction.

10. Can the PR6424/101-021 replace another PR6424 model?

Not automatically. Different suffixes may indicate variations in cable length, mounting configuration, connector arrangement, or converter compatibility. Always compare the complete model numbers and technical specifications before replacement.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/101-021, verify the complete part number and compare it with the sensor installed on the machine. Confirm the sensor head diameter, cable arrangement, connector type, mounting details, and compatible converter.

For critical turbine and compressor applications, probe compatibility should be assessed as part of the complete measurement chain. A replacement sensor should match the converter and extension cable requirements to maintain the intended measurement sensitivity and accuracy.

For spare-parts procurement, request clear photographs of the sensor label, probe head, cable, and connector. Confirm whether the product is supplied with an extension cable or other accessories, as these may be separate items.

During maintenance, inspect the sensor mounting, cable insulation, connector condition, and mechanical clearance around the probe. Check that the sensor has not been struck or displaced and that the cable has not been exposed to excessive bending or mechanical stress.

After replacement, verify the initial air gap and confirm that the signal converter produces the expected measurement output. Record the installed sensor model and relevant calibration information for future maintenance.

Conclusion

The Epro PR6424/101-021 16 mm Eddy Current Sensor is designed for non-contact monitoring of shaft displacement and vibration in critical rotating machinery. As part of the PR6424 family, it provides a typical sensitivity of 4 V/mm, a static measuring range of ±2.0 mm, and a dynamic range of 0–1,000 μm.

Its measurement capabilities make it suitable for properly configured monitoring systems used with turbines, compressors, pumps, fans, and other rotating equipment. For reliable operation, the sensor must be matched with the correct extension cable, signal converter, target material, and installation arrangement.

When sourcing or replacing this model, checking the complete PR6424/101-021 configuration is essential to ensure that the probe fits the existing machinery monitoring system.