Product Overview

The EPRO PR6424/014-121 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of rotating machinery. Manufactured under the EPRO product line associated with Emerson, the PR6424 series is widely used in machinery protection and condition-monitoring applications involving turbines, compressors, pumps, generators, and other critical rotating equipment.

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 measurement principle allows the probe to monitor shaft movement while the machine is operating. It can provide information about radial and axial shaft displacement, vibration, position, eccentricity, and rotational reference conditions when used in a suitable measurement system.

The PR6424/014-121 belongs to the 16 mm sensor family. Its sensing head has a nominal diameter of 16 mm, and the listed probe length is approximately 121 mm. The supplied product weight is approximately 0.2 kg.

The PR6424 family offers a nominal static measurement range of ±2.0 mm and a sensitivity of 4 V/mm when configured with the appropriate signal converter and measurement target. These characteristics make it suitable for applications requiring continuous monitoring of shaft position and dynamic movement.

The sensor is normally part of a complete measurement chain that includes the probe, an extension cable where required, and a compatible signal converter. The converter conditions the probe signal and provides an output that can be processed by a machinery protection or monitoring system.

For replacement projects, the complete model number is important. Cable configuration, connector type, probe characteristics, and converter compatibility should all be checked before purchasing a replacement.

Technical Specifications

Note: The measurement and environmental values above describe typical PR6424 family specifications. The exact cable arrangement, connector, mounting dimensions, and approved operating limits should be confirmed against the documentation for the complete PR6424/014-121 configuration.

Function and Working Principle

The PR6424/014-121 operates using the eddy current measurement principle. It generates an electromagnetic field at the sensing tip and detects changes in that field caused by the distance between the probe and a conductive target.

1. Non-Contact Displacement Measurement

The sensor is installed near a conductive shaft or other suitable measurement surface. When the target moves closer to or farther away from the probe, the electrical characteristics of the sensing circuit change.

A compatible signal converter interprets these changes and converts them into a usable measurement signal. The resulting output can represent the relative distance between the probe and the target surface.

Because the probe does not need to touch the rotating shaft, it can continuously monitor movement without introducing mechanical contact or friction at the measurement point.

2. Eddy Current Measurement Principle

An alternating electrical signal energizes the sensor coil and creates an electromagnetic field around the probe tip. When a conductive metal target enters this field, eddy currents are induced in the target.

These currents influence the electromagnetic characteristics of the probe. The resulting change in impedance is related to the distance between the sensor and the target.

The measurement is then processed by a compatible converter to produce an output proportional to the measured gap.

The target material is important because electrical conductivity and magnetic properties affect the sensor’s response. PR6424 systems are calibrated for specified ferromagnetic target materials, with 42CrMo4 steel commonly used as the standard reference material.

3. Shaft Vibration Monitoring

Rotating machinery can experience radial or axial movement caused by imbalance, misalignment, bearing wear, thermal expansion, and other mechanical conditions.

When installed at an appropriate measurement position, the PR6424 probe can detect changes in shaft-to-probe distance. These measurements can be used to assess shaft vibration and identify changes in mechanical behavior.

The sensor’s dynamic measurement capability makes it useful in machinery condition-monitoring systems where continuous vibration information is required.

4. Shaft Position and Axial Displacement

In addition to vibration measurement, the PR6424 family can be used to monitor shaft position. Axial displacement measurements are useful for observing changes in the position of a rotating shaft relative to a fixed reference point.

This information can help operators identify abnormal shaft movement and assess machine operating conditions.

5. Signal Conversion and Monitoring

The probe is not normally used as a standalone monitoring instrument. It forms part of a measurement chain that includes a compatible signal converter.

The converter processes the sensor’s electrical response and generates a standardized measurement output for a machinery protection system, monitoring rack, or diagnostic instrument.

The complete system must be configured and calibrated as a matched combination. Probe type, extension cable, converter model, cable length, and target material all influence measurement accuracy.

Role in Industrial Machinery Protection Systems

The PR6424/014-121 is designed for use in machinery monitoring applications where accurate shaft displacement information is important for equipment protection and maintenance.

Turbine Monitoring

Steam turbines, gas turbines, and hydro turbines contain rotating assemblies that operate under demanding mechanical and thermal conditions. Shaft vibration and displacement measurements help monitoring systems evaluate machine behavior during startup, normal operation, and shutdown.

A suitable PR6424 measurement chain can provide shaft movement information for machinery protection and condition assessment.

Compressor Monitoring

Industrial compressors are often critical to production processes. Changes in shaft vibration or position may indicate mechanical conditions that require investigation.

Non-contact displacement measurements can support the monitoring of compressor rotor behavior and help maintenance personnel identify developing problems.

Pump Monitoring

Large industrial pumps may experience shaft movement caused by bearing conditions, hydraulic forces, alignment problems, or mechanical wear.

The PR6424 sensor can be installed at suitable measurement locations to provide shaft displacement information for a compatible monitoring system.

Generator Monitoring

Generators contain rotating assemblies that require continuous mechanical condition monitoring. Shaft position and vibration measurements can help identify changes in rotor behavior and support planned maintenance.

Machinery Protection Integration

When connected to a compatible monitoring system, the sensor contributes measurement data that can be used for alarm generation, trend analysis, and equipment protection.

The sensor itself does not independently determine the complete health condition of a machine. Its measurements must be interpreted alongside other monitoring channels, operating parameters, and maintenance information.

Industrial Applications

The EPRO PR6424/014-121 is suitable for selected applications involving critical rotating machinery and non-contact shaft measurement.

1. Steam Turbines

Steam turbines operate at high rotational speeds and under changing thermal and mechanical conditions. Continuous shaft displacement monitoring helps operators observe vibration and position changes.

The PR6424 series can be used in suitable turbine monitoring arrangements to measure radial or axial shaft movement.

2. Gas Turbines

Gas turbines are used in power generation and industrial mechanical-drive applications. Their rotating components require reliable condition monitoring to support safe and stable operation.

A properly installed eddy current measurement system can provide information about shaft movement and vibration.

3. Industrial Compressors

Centrifugal and other high-speed compressors may require continuous shaft monitoring. Changes in rotor behavior can be associated with imbalance, bearing problems, alignment changes, or operating-condition variations.

The PR6424 sensor can support these monitoring functions when paired with a compatible converter.

4. Industrial Pumps

Large process pumps are commonly used in chemical plants, refineries, power stations, and water-treatment facilities.

Non-contact shaft measurement can help maintenance teams observe mechanical movement and identify changes that may require further inspection.

5. Electric Generators

Generator monitoring systems use shaft vibration and displacement measurements to evaluate rotating equipment behavior.

The PR6424 probe can form part of a larger monitoring arrangement for generator rotor condition assessment.

6. Fans and Other Rotating Equipment

Large industrial fans and auxiliary rotating equipment may also require vibration monitoring. Where the shaft material, mounting arrangement, and measurement requirements are suitable, an eddy current sensor can provide non-contact displacement information.

Installation and System Integration

Correct installation is essential for reliable measurements. The probe must be positioned and calibrated according to the target material, measurement range, mechanical arrangement, and converter specifications.

1. Confirm the Probe Model

Before installation, verify the complete model number PR6424/014-121. Do not assume that every PR6424 probe has identical cable lengths, connector arrangements, mounting dimensions, or calibration characteristics.

Check the probe label and compare the replacement unit with the original installation documentation.

2. Select the Measurement Position

The probe should be mounted at the measurement location specified by the machinery design. The sensing tip must face a suitable conductive target surface and maintain the required mechanical clearance.

For shaft vibration monitoring, probe placement and orientation should follow the machinery manufacturer’s measurement arrangement.

3. Check Target Material

The PR6424 family is calibrated for specified ferromagnetic materials. The target material affects the sensor response and therefore must be considered during installation and calibration.

Where the target material differs from the standard reference material, the measurement chain may require an appropriate calibration procedure.

4. Set the Initial Air Gap

The distance between the sensor tip and the target surface must be set within the specified operating range.

For the PR6424 family, the nominal center air gap is approximately 2.7 mm under standard conditions. The actual installation setting must follow the matched converter and probe documentation.

An incorrect initial gap can reduce the available measurement range or cause inaccurate readings.

5. Install the Cable Correctly

Route the sensor cable away from high-voltage power cables and sources of electromagnetic interference where possible.

Avoid sharp bends, excessive tension, mechanical damage, and contact with surfaces exceeding the cable’s permitted temperature. The minimum bending radius and cable routing requirements should be taken from the applicable installation documentation.

6. Connect the Signal Converter

Connect the probe to the correct extension cable and signal converter. Verify connector compatibility, cable length, and the required measurement-chain configuration.

The converter must be designed for the relevant PR6424 probe arrangement. Using an incompatible converter or an incorrect cable combination can affect measurement accuracy and signal stability.

7. Calibrate and Verify the Measurement

After installation, confirm the initial gap, converter output, measurement polarity, and signal response. Where possible, compare the output with a known mechanical reference or an approved calibration procedure.

Record the installation gap and relevant configuration information for future maintenance.

Compatible System Components

The PR6424/014-121 is normally used as part of a complete eddy current measurement system. The following components may be involved, depending on the application and system design.

Not every component listed above is automatically compatible with every PR6424 configuration. The exact sensor, extension cable, converter, and monitoring-system combination must be confirmed before installation.

Alternative Models and Replacement Considerations

The PR6424 belongs to the EPRO family of eddy current displacement sensors. Other models may have similar functions but different measurement ranges, probe dimensions, sensitivity, or temperature characteristics.

When selecting a replacement, verify the following:

• Complete probe model number.
• Sensor head diameter and mounting thread.
• Probe length and mechanical installation dimensions.
• Cable type and overall cable length.
• Connector and extension cable arrangement.
• Compatible signal converter.
• Measurement range and sensitivity.
• Target material and calibration requirements.
• Operating temperature and environmental conditions.
• Monitoring-system input requirements.

A probe with the same 16 mm head diameter is not necessarily a direct replacement. Its electrical characteristics and measurement-chain compatibility must also be checked.

Key Advantages

Non-Contact Measurement

The eddy current principle allows the sensor to measure shaft displacement without physical contact with the rotating surface. This supports continuous measurement without introducing contact wear at the sensing point.

Suitable for Critical Rotating Machinery

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

Shaft Vibration and Position Monitoring

The sensor can provide displacement information for monitoring radial vibration, axial movement, and shaft position when installed in a suitable measurement arrangement.

16 mm Sensor Head

The 16 mm sensing head is designed for applications requiring the PR6424 measurement characteristics and corresponding mounting arrangement.

Stable Measurement Performance

The PR6424 family provides a nominal sensitivity of 4 V/mm and linearity of up to ±1.5% under specified conditions. Proper calibration and correct target material are essential for achieving the intended performance.

Integration with Machinery Monitoring Systems

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

Industrial Measurement Application

The sensor is intended for industrial environments where continuous information about rotating equipment behavior supports maintenance planning and operational monitoring.

Technical FAQs

1. What is the EPRO PR6424/014-121?

The EPRO PR6424/014-121 is a 16 mm eddy current displacement sensor used for non-contact measurement of shaft vibration, displacement, and position in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm.

3. What is the weight of the PR6424/014-121?

The supplied product weight is approximately 0.2 kg.

4. What measurement range does the PR6424 series provide?

The standard PR6424 family has a static measurement range of ±2.0 mm. Its typical dynamic measurement range is 0 to 1,000 μm peak-to-peak under the specified measurement conditions.

5. What is the sensitivity of the PR6424 sensor?

The standard PR6424 family sensitivity is 4 V/mm when used with the appropriate signal converter and specified target material.

6. Does the sensor require a signal converter?

Yes. The probe normally operates as part of a complete measurement chain that includes a compatible signal converter. The converter processes the probe response and produces a usable measurement output.

7. What machinery can use the PR6424/014-121?

Typical applications include steam turbines, gas turbines, hydro turbines, industrial compressors, pumps, generators, and other rotating machinery requiring shaft displacement monitoring.

8. Can the PR6424 measure shaft vibration?

Yes. When correctly installed and connected to a compatible converter and monitoring system, the sensor can measure dynamic shaft displacement associated with vibration.

9. What target material is suitable?

The PR6424 family is designed for use with specified ferromagnetic target materials. 42CrMo4 steel is commonly used as the standard calibration reference. Target material should be confirmed during system setup.

10. Can another 16 mm sensor replace the PR6424/014-121?

Not automatically. The replacement must match the required electrical characteristics, cable arrangement, mounting dimensions, measurement range, and signal converter compatibility.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/014-121, verify the complete model number and compare the product with the sensor installed in the existing machinery. Pay particular attention to the 16 mm sensing head, probe length, cable configuration, connector type, and compatible signal converter.

For replacement applications, confirm whether the original installation uses a complete probe-and-cable assembly or a separate extension cable. Differences in cable length or connector configuration can prevent a replacement probe from operating correctly with the existing measurement chain.

For used or surplus sensors, request clear photographs of the product label, sensing tip, threaded body, cable, and connector. Check for visible damage, cable deformation, corrosion, and signs of previous mechanical impact.

During maintenance, inspect the probe mounting arrangement and cable routing. Avoid applying excessive mechanical force to the sensor body or cable. Confirm the measurement gap and signal output after installation, and document the final configuration.

For critical machinery, sensor replacement should be followed by verification of the complete measurement chain. This includes the probe, cable, signal converter, monitoring channel, and alarm settings.

Conclusion

The EPRO PR6424/014-121 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in industrial rotating machinery. Its 16 mm sensing head and PR6424 family measurement characteristics make it suitable for selected turbine, compressor, pump, and generator monitoring applications.

With a typical static measurement range of ±2.0 mm, sensitivity of 4 V/mm, and linearity of up to ±1.5% under specified conditions, the PR6424 family supports continuous machinery monitoring when installed as part of a correctly configured measurement chain.

For industrial maintenance and replacement projects, confirming the complete model number, cable configuration, signal converter compatibility, and target material is essential for reliable operation.