Product Overview

The Epro PR6424/019-021 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the mechanical condition of rotating machinery. It belongs to the EPRO PR6424 series, developed for applications where accurate measurement of shaft vibration, displacement, position, and eccentricity is important for equipment protection and condition monitoring.

Manufactured under the EPRO product line associated with Emerson, the PR6424 series is commonly used in critical rotating equipment such as steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These machines operate under demanding mechanical and thermal conditions. Continuous monitoring of shaft movement can help operators identify abnormal operating conditions before they develop into serious equipment problems.

The PR6424/019-021 uses eddy current measurement technology. Instead of physically contacting the rotating shaft, the sensor detects changes in the distance between its sensing tip and a conductive target surface. The resulting measurement signal can be processed by a compatible signal converter and machinery protection or monitoring system.

This particular product is identified as a 16 mm sensor head model. The supplied product information specifies a sensor head diameter of 16 mm and a weight of approximately 0.2 kg. The PR6424 series has a typical sensitivity of 4 V/mm and a static measurement range of ±2.0 mm. Its dynamic measurement capability supports vibration measurements up to 1,000 μm, subject to the applicable system configuration.

The sensor is designed for integration into machinery monitoring systems rather than use as a standalone display device. Correct operation depends on the sensor, extension cable where required, signal converter, target material, installation gap, and monitoring equipment being compatible.

For maintenance teams, the PR6424/019-021 can serve as a replacement component in existing EPRO-based machinery monitoring installations. Before ordering, the complete model number and cable configuration should be checked against the installed sensor.

Technical Specifications

Note: The technical values above describe the PR6424 16 mm sensor family. Confirm the exact cable, connector, temperature rating, and installation configuration for PR6424/019-021 using its product label and applicable documentation.

Function and Working Principle

The PR6424/019-021 measures the distance between the sensor tip and a conductive target without physical contact. This makes it suitable for monitoring rotating shafts where conventional contact-based measurement would be impractical.

1. Eddy Current Measurement Principle

An eddy current sensor contains an electrical coil inside its sensing head. When the sensor is supplied with the appropriate excitation signal, the coil generates an electromagnetic field.

When a conductive target, such as a ferromagnetic steel shaft, is positioned near the sensing tip, the electromagnetic field induces eddy currents in the target surface. These currents influence the electrical characteristics of the sensor coil.

As the distance between the sensor and target changes, the strength of this interaction also changes. The associated electrical response can be converted into a measurement signal representing the relative displacement between the probe and the target.

This method allows the sensor to measure shaft movement without requiring direct mechanical contact.

2. Shaft Displacement Measurement

Shaft displacement monitoring is important in rotating machinery because excessive movement can indicate changes in bearing condition, shaft alignment, mechanical clearance, or operating load.

The PR6424 series provides a static measurement range of approximately ±2.0 mm. This range can be used to monitor shaft position relative to the installed sensor.

The actual measurement depends on the probe’s installation position, initial air gap, target material, and calibration of the associated measurement system.

3. Shaft Vibration Measurement

Rotating shafts may move continuously during operation due to mechanical vibration. An eddy current sensor can detect these small changes in shaft position and provide a signal for vibration analysis.

The PR6424 family supports dynamic measurement from 0 to 1,000 μm. This capability is useful in machinery monitoring systems that evaluate shaft vibration trends and identify abnormal mechanical behavior.

Vibration monitoring can help maintenance personnel identify developing problems such as rotor imbalance, misalignment, looseness, or bearing-related changes. However, identifying a specific fault requires analysis of the complete vibration data and operating conditions rather than relying on one sensor reading.

4. Position and Eccentricity Monitoring

The sensor can also be used to measure shaft position and eccentricity. Eccentricity refers to a condition in which a rotating shaft or rotor does not maintain a uniform geometric relationship with its intended rotational center.

Changes in eccentricity may be associated with mechanical deformation, assembly conditions, thermal effects, or rotor-related problems.

Continuous position measurements provide useful information for monitoring equipment behavior during startup, normal operation, and shutdown.

5. Speed and Key Reference Applications

Eddy current sensing systems can also support speed-related and key-reference measurements when correctly configured. A compatible monitoring system can interpret changes in the probe signal associated with the passing target features.

The suitability of a particular probe installation depends on the shaft geometry, target characteristics, measurement arrangement, and signal-processing equipment.

Role in Industrial Machinery Protection Systems

The PR6424/019-021 is typically installed as part of a complete machinery monitoring arrangement. Its measurement signal is processed by compatible electronics before being used for monitoring, alarm generation, or protective control.

Sensor Probe

The sensor probe is installed near the rotating shaft with a specified initial gap. It detects changes in the distance between the sensing tip and the target surface.

The probe’s mounting position and mechanical stability are essential for accurate measurement. Incorrect installation can introduce measurement errors or cause the sensor to produce unreliable readings.

Extension Cable and Connector

Depending on the system configuration, the probe may connect directly to compatible signal-processing equipment or through an extension cable.

Cable type, total electrical length, connector design, shielding, and electrical compatibility must be verified. A replacement probe should not be assumed compatible merely because it belongs to the same PR6424 family.

Signal Converter

The signal converter provides the electrical interface between the probe assembly and the monitoring system. It processes the sensor response and produces a signal suitable for measurement and analysis.

A compatible converter is essential because the sensor and converter must operate as a matched measurement system. Incorrect combinations can result in inaccurate readings or unstable signals.

Machinery Monitoring System

The processed signal can be supplied to a machinery monitoring system for continuous display, trend recording, alarm management, and protective functions.

In critical rotating equipment, these measurements may form part of a broader machinery protection strategy. The monitoring system evaluates the sensor signal together with other operating parameters to determine whether the equipment is operating within acceptable limits.

Industrial Applications

The PR6424 16 mm Eddy Current Sensor is designed for demanding rotating machinery applications. Its non-contact measurement principle makes it particularly useful where shaft movement must be monitored continuously.

1. Steam Turbines

Steam turbines operate at high rotational speeds and under changing thermal and mechanical loads. Shaft vibration and displacement measurements are important for monitoring rotor behavior and identifying abnormal operating conditions.

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

Monitoring data may help maintenance teams evaluate vibration trends, rotor stability, and changes in shaft position during operation.

2. Gas Turbines

Gas turbines are used in power generation and industrial mechanical-drive applications. Their rotating assemblies operate under demanding temperature, speed, and vibration conditions.

Non-contact shaft monitoring provides information about rotor movement without introducing mechanical contact with the rotating component.

The sensor can be incorporated into an appropriate monitoring arrangement for evaluating shaft displacement and vibration.

3. Hydro Turbines

Hydroelectric generating equipment contains large rotating assemblies that require long-term condition monitoring. Shaft movement measurements can provide useful information about mechanical stability and operating behavior.

In suitable hydro turbine installations, eddy current sensors can monitor shaft position and vibration as part of the overall machinery monitoring system.

4. Industrial Compressors

Centrifugal compressors and other rotating compressor types may experience changes in vibration and shaft position due to operating conditions, mechanical wear, or installation problems.

The PR6424 sensor can support non-contact shaft measurement in compatible compressor monitoring systems.

Continuous measurements can help maintenance teams observe changes over time and plan inspections based on equipment condition.

5. Industrial Pumps

Large industrial pumps are often used in chemical processing, water treatment, power plants, and other process industries.

Shaft vibration and displacement measurements can help identify changes in mechanical behavior. A properly installed eddy current sensor can provide information for monitoring the rotating assembly.

6. Industrial Fans

Large fans and blower systems may experience vibration changes caused by imbalance, misalignment, bearing problems, or mechanical looseness.

The PR6424 series can be used in suitable monitoring configurations to measure shaft movement and support condition-based maintenance.

Installation and System Integration

Correct installation is essential for obtaining reliable measurement results from an eddy current sensor.

1. Verify the Complete Model Number

Before installation, confirm that the replacement sensor is the exact PR6424/019-021 model required by the equipment.

The PR6424 series includes different probe configurations, cable arrangements, and connection options. Similar-looking sensors may not have identical electrical or mechanical characteristics.

Check the complete model designation, cable length, connector type, and any associated accessories.

2. Prepare the Mounting Location

The sensor should be installed in a stable mounting arrangement that maintains the required position relative to the shaft.

The mounting surface should be clean and mechanically secure. Excessive movement of the sensor holder can introduce unwanted measurement variations.

For the PR6424 series, the typical mounting thread is M18 × 1.5. Confirm the mechanical details of the exact probe before preparing or modifying the mounting point.

3. Set the Initial Air Gap

The initial distance between the sensor tip and the target surface is an important installation parameter.

The PR6424 family has a nominal center air gap of approximately 2.7 mm. The actual gap must be established according to the applicable calibration procedure and the associated signal converter.

An incorrect gap can reduce measurement accuracy or cause the sensor to operate outside its linear measurement region.

4. Check the Target Surface

The sensor is designed for measurement against a suitable conductive target. The PR6424 specification identifies ferromagnetic steel, with 42CrMo4 as the standard reference material.

Target material and surface characteristics can influence sensor performance. Engineers should confirm that the installed shaft material is appropriate for the measurement system.

The recommended shaft diameter for the PR6424 series is at least 80 mm.

5. Route and Protect the Cable

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

Avoid sharp bends, crushing, or excessive tension. Follow the cable’s minimum bending radius and installation instructions for the exact cable configuration.

Where the installation uses an armored cable, verify the required mechanical protection and grounding arrangement.

6. Connect the Compatible Signal Converter

Connect the probe to the specified compatible signal converter using the correct cable and connector arrangement.

Do not assume that all PR6424 probes can be connected to every converter without checking the system configuration. Probe type, cable characteristics, and converter compatibility must be confirmed.

7. Calibrate and Verify the Measurement

After installation, establish the required initial gap and perform the applicable calibration or verification procedure.

Check the measurement output under stationary conditions before evaluating vibration during normal machine operation.

Compare the sensor reading with the monitoring system’s expected values and verify that the signal remains stable during operation.

Compatible System Components

The PR6424/019-021 is normally used with other components in a machinery monitoring system.

These components represent a typical system architecture. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 series contains different model suffixes and mechanical configurations. A replacement should be selected by comparing the complete part number and system requirements.

Before selecting an alternative, compare:

• Sensor head diameter.
• Complete probe model number.
• Measurement range and sensitivity.
• Sensor mounting thread and mechanical length.
• Cable type and total cable length.
• Connector and extension cable arrangement.
• Operating temperature rating.
• Target material and shaft diameter.
• Signal converter compatibility.
• Monitoring system configuration.

A sensor from the same product family is not necessarily a direct replacement. Even small differences in cable length, connector configuration, or probe characteristics can affect system compatibility.

Key Advantages

Non-Contact Measurement

The sensor measures shaft movement without physically contacting the rotating surface. This makes it suitable for continuous monitoring of high-speed machinery.

High Measurement Sensitivity

The PR6424 family provides a typical sensitivity of 4 V/mm, supporting the measurement of small changes in shaft position.

Static and Dynamic Monitoring

The sensor supports both static displacement measurement and dynamic vibration measurement within the specified operating range.

Industrial Machinery Applications

The PR6424 series is designed for use in turbines, compressors, pumps, fans, and other critical rotating equipment.

Stainless Steel Sensor Sleeve

The stainless steel sleeve provides a robust mechanical structure for industrial sensor installation.

PTFE Cable Construction

The series uses PTFE cable material, supporting applications where the specified cable temperature and environmental limits are appropriate.

Integration with Machinery Monitoring Systems

The sensor can be incorporated into compatible signal-conversion and machinery protection systems for continuous measurement and condition monitoring.

Technical FAQs

1. What is the Epro PR6424/019-021?

The Epro PR6424/019-021 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 supplied product specification identifies a sensor head diameter of 16 mm.

3. What is the measurement principle?

It uses eddy current technology. An electromagnetic field interacts with the conductive shaft surface, and changes in the distance between the sensor and target affect the sensor’s electrical response.

4. What is the measurement range of the PR6424 series?

The published PR6424 family specification gives a static range of approximately ±2.0 mm and a dynamic range of 0 to 1,000 μm.

5. What is the sensitivity?

The typical sensitivity is 4 V/mm, with a specified linearity of no more than ±1.5%.

6. What material should the sensor target be?

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

7. Where is the PR6424/019-021 commonly used?

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

8. What is the weight of the sensor?

The supplied product weight is approximately 0.2 kg. The manufacturer’s series specification also gives approximately 200 grams for the sensor with a 1-meter cable and without armor.

9. Does the sensor connect directly to a PLC?

It is generally used with compatible signal-conversion and machinery monitoring equipment. Direct connection to a PLC should not be assumed. The required signal conditioning and interface depend on the installed system.

10. Can another PR6424 model replace the PR6424/019-021?

Not automatically. Confirm the probe dimensions, suffix, cable length, connector, measurement characteristics, and converter compatibility before substitution.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/019-021, verify the complete part number printed on the sensor identification label. The PR6424 family includes several variants, and their cable lengths, connector arrangements, and mechanical configurations may differ.

For replacement projects, compare the existing sensor with the proposed unit before ordering. Check the sensor head diameter, mounting thread, cable configuration, connector type, and compatibility with the installed signal converter.

For used or surplus equipment, request clear photographs of the probe, identification label, cable, and connector. Confirm the physical condition of the sensing tip and cable insulation. Where possible, request test information or evidence that the sensor has been checked with a compatible measurement system.

During routine maintenance, inspect the mounting arrangement for looseness, check the cable for mechanical damage, and verify that the sensor gap remains within the required range. Monitor measurement trends and investigate unexpected changes rather than relying only on individual readings.

Correct installation and compatibility verification are essential for maintaining reliable shaft displacement and vibration measurements in critical rotating machinery.

Conclusion

The Epro PR6424/019-021 16 mm Eddy Current Sensor is an industrial non-contact measurement probe intended for shaft displacement, vibration, position, and eccentricity monitoring in rotating machinery.

Its PR6424 series characteristics include 4 V/mm sensitivity, a static measurement range of ±2.0 mm, and dynamic measurement capability up to 1,000 μm. With a 16 mm sensor head and an approximate supplied weight of 0.2 kg, it can be used in compatible machinery monitoring installations across power generation and industrial process applications.

For maintenance and procurement, the most important considerations are exact model identification, cable and connector compatibility, correct mounting gap, target material, and signal converter matching. These checks help ensure that a replacement sensor can operate reliably within the existing machinery protection system.