Product Overview

The Epro PR6424/017-021 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the operating condition of rotating machinery. Part of the PR6424 sensor family from Epro, now associated with Emerson, it is used to measure shaft vibration, displacement, position, and eccentricity in critical industrial 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 rotating shaft. This makes it suitable for continuous monitoring applications where mechanical contact could cause wear or interfere with measurement accuracy.

The PR6424 family is designed for machinery such as steam turbines, gas turbines, compressors, pumps, fans, and hydro turbines. Its measurements can be used by machinery protection and condition-monitoring systems to identify abnormal shaft movement and support preventive maintenance.

The PR6424/017-021 has a nominal sensor head diameter of 16 mm. Its supplied listing weight is 0.2 kg. The sensor operates as part of a measurement chain that normally includes a compatible extension cable and signal converter. The complete system converts changes in the probe-to-target distance into an electrical signal for monitoring equipment.

For procurement and replacement, it is important to verify the complete model suffix, cable arrangement, connector type, probe length, and converter compatibility. Different PR6424 configurations may share the same sensor diameter while having different mechanical and electrical arrangements.

Technical Specifications

Note: The measurement and environmental values above are PR6424 family specifications. Confirm the exact cable, connector, probe length, and temperature rating of the PR6424/017-021 configuration before installation.

Function and Working Principle

The PR6424/017-021 uses the eddy current principle to measure the distance between the sensor tip and a conductive target. This technology is widely used in rotating machinery monitoring because it supports non-contact measurement of shaft movement.

1. Eddy Current Measurement

The sensor generates an electromagnetic field around its sensing tip. When a conductive metallic target, such as a rotating steel shaft, enters this field, eddy currents are induced in the target.

These currents affect the electrical characteristics of the sensor coil. The resulting change in impedance is related to the distance between the sensor tip and the target surface.

With a compatible signal converter, this change can be converted into an electrical output proportional to the measured gap.

2. Shaft Displacement Measurement

The sensor can measure changes in the position of a shaft relative to its mounting point. This information is useful for identifying abnormal shaft movement, mechanical misalignment, and changes in rotor position.

Static displacement measurements can help evaluate shaft position, while dynamic measurements provide information about shaft movement during operation.

3. Vibration Monitoring

During normal operation, rotating shafts may exhibit small movements caused by imbalance, misalignment, bearing conditions, or other mechanical effects.

The PR6424 sensor detects these movements without touching the shaft. Its dynamic measurement capability allows compatible monitoring equipment to analyze vibration signals and identify changes in machinery behavior.

4. Position and Eccentricity Detection

The sensor can also be used to monitor shaft position and eccentricity. Eccentricity refers to the deviation of a rotating shaft from its intended geometric center.

Changes in eccentricity may indicate mechanical problems or abnormal operating conditions. Continuous measurement provides useful information for maintenance personnel and machinery protection systems.

5. Signal Conversion

The probe is normally connected to a compatible signal converter through the specified cable arrangement. The converter conditions the sensor signal and provides an output suitable for machinery monitoring equipment.

The complete measurement chain must be calibrated and configured for the correct probe, extension cable, target material, and converter combination.

Role in Industrial Control and Machinery Protection Systems

The PR6424/017-021 is primarily a sensing component in machinery monitoring systems. It provides measurement information that can be used by protection devices, condition-monitoring platforms, and industrial control equipment.

1. Turbine Monitoring

Steam and gas turbines contain high-speed rotating components that require continuous monitoring. The sensor can measure shaft vibration and displacement, helping operators identify abnormal rotor movement.

Measurements can be integrated into machinery protection systems to support alarm and shutdown decisions according to the plant’s protection philosophy.

2. Compressor Condition Monitoring

Industrial compressors operate under demanding mechanical and thermal conditions. Shaft vibration and displacement measurements provide information about the condition of rotating assemblies.

The sensor can contribute to a monitoring arrangement that helps maintenance teams detect changes before they develop into more serious equipment problems.

3. Integration with Machinery Monitoring Equipment

The sensor is not a standalone PLC input device in the usual sense. It normally requires a compatible signal converter or monitoring interface before its output is connected to a monitoring or protection system.

The converter selection, cable configuration, and monitoring input must all match the sensor’s electrical characteristics.

4. Predictive Maintenance

Continuous measurement data can be reviewed over time to identify changes in vibration or shaft position. This supports condition-based maintenance by allowing maintenance teams to investigate developing abnormalities rather than relying only on fixed maintenance intervals.

The sensor provides measurement data; diagnosis and maintenance decisions depend on the monitoring system, operating history, and engineering analysis.

Industrial Applications

The Epro PR6424/017-021 is designed for non-contact monitoring of rotating machinery in industrial environments.

1. Steam Turbines

Steam turbines operate at high rotational speeds and require reliable monitoring of shaft movement. Eddy current sensors can measure radial and axial displacement, helping operators monitor rotor behavior.

The PR6424 family is suitable for applications where continuous shaft vibration and position measurements are required.

2. Gas Turbines

Gas turbines are used in power generation and industrial processes. Their rotating assemblies operate under demanding temperature and mechanical conditions.

A properly configured PR6424 measurement chain can provide shaft displacement and vibration information for compatible turbine monitoring systems.

3. Hydro Turbines

Hydroelectric generating equipment contains large rotating assemblies that require condition monitoring. Eddy current probes can help measure shaft movement and detect changes in rotor behavior.

These measurements are useful for evaluating mechanical stability and supporting maintenance planning.

4. Industrial Compressors

Centrifugal and other large industrial compressors require monitoring of rotating shafts and bearings. Shaft displacement measurements can help identify vibration changes and abnormal mechanical movement.

The sensor may be incorporated into a compressor protection system when the probe, converter, and monitoring hardware are compatible.

5. Pumps and Fans

Large industrial pumps and fans may operate continuously in power plants, chemical facilities, and manufacturing installations. Monitoring shaft vibration and position can help maintenance teams identify changes in equipment condition.

The sensor should be selected according to shaft dimensions, mounting conditions, target material, and required measurement range.

Installation and System Integration

Correct installation is essential for measurement accuracy and long-term reliability.

1. Verify the Sensor Configuration

Before installation, confirm the complete PR6424/017-021 model designation. Check the probe’s mechanical dimensions, cable length, connector type, and compatible signal converter.

Do not assume that every PR6424 sensor variant uses the same cable or connection arrangement.

2. Select the Correct Mounting Position

Install the sensor in the position specified by the machinery monitoring design. The sensing tip must face the intended shaft measurement surface and maintain the required operating gap.

The mounting arrangement should be mechanically stable. Loose mounting hardware or excessive vibration at the mounting point can affect measurement quality.

3. Check the Target Material

PR6424 family specifications identify ferromagnetic steel, typically 42CrMo4, as the standard target material.

The target material affects sensor calibration and measurement characteristics. If the actual shaft material differs from the standard, verify whether special calibration or configuration is necessary.

4. Set the Correct Air Gap

The sensor-to-shaft distance must be adjusted according to the manufacturer’s installation procedure and the converter’s calibration requirements.

The PR6424 family specification gives a nominal center air gap of approximately 2.7 mm. This value should not be treated as a substitute for the exact installation instructions for the selected probe and converter.

5. Route the Sensor Cable Correctly

Route the sensor cable away from sources of electrical interference and mechanical damage. Avoid sharp bends, excessive tension, and contact with hot or moving components.

Observe the specified minimum bending radius and cable temperature limits. Use the correct extension cable and connector arrangement for the installed configuration.

6. Connect the Compatible Signal Converter

The sensor should be paired with a compatible converter. Confirm the required electrical characteristics, cable arrangement, and calibration before connecting it to the monitoring equipment.

An incorrect converter or extension cable may produce inaccurate readings or prevent the measurement chain from operating correctly.

7. Commission and Verify Measurements

After installation, verify the sensor gap, cable connections, converter configuration, and output signal. Compare the measured values with the expected operating conditions.

Record the installation details and calibration information so that future maintenance personnel can reproduce the correct setup.

Compatible System Components

A PR6424 measurement arrangement normally includes the probe, extension cable, signal converter, and monitoring equipment.

Not all listed components are included with the sensor. Verify the complete bill of materials when purchasing a replacement or assembling a new measurement system.

Alternative Models and Replacement Considerations

The PR6424 family includes different sensor configurations. Although several variants share a 16 mm sensing diameter, their cable arrangements, mounting dimensions, and electrical characteristics may differ.

Before replacing the sensor, compare:

• Complete model number and suffix.
• Sensor head diameter and mechanical dimensions.
• Thread type and mounting arrangement.
• Cable length and connector type.
• Sensor-to-converter compatibility.
• Static and dynamic measurement ranges.
• Sensitivity and calibration requirements.
• Operating temperature and environmental limits.
• Target material and shaft dimensions.
• Monitoring system input requirements.

A sensor with the same nominal diameter is not necessarily a direct replacement. The complete measurement chain must be checked before installation.

Key Advantages

Non-Contact Measurement

The sensor measures shaft movement without physical contact, avoiding direct mechanical wear between the sensing element and the rotating target.

Suitable for Critical Rotating Machinery

The PR6424 family is designed for machinery such as turbines, compressors, pumps, and fans where shaft vibration and displacement monitoring are important.

Static and Dynamic Measurement

The family supports both shaft position measurement and dynamic vibration measurement, allowing a single measurement technology to serve multiple monitoring functions.

High Measurement Sensitivity

The specified family sensitivity of 4 V/mm supports the detection of small changes in the probe-to-target distance when used with the correct converter.

Industrial Construction

The stainless-steel sleeve and PTFE cable construction are intended for industrial measurement environments within the specified operating limits.

Integration with Machinery Monitoring Systems

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

Technical FAQs

1. What is the Epro PR6424/017-021?

It is a 16 mm eddy current displacement sensor designed for non-contact measurement of shaft vibration, displacement, position, and eccentricity in rotating machinery.

2. What is the sensor head diameter?

The nominal sensor head diameter is 16 mm.

3. What is the measurement principle?

It uses the eddy current principle. Changes in the distance between the sensor tip and a conductive target affect the electrical characteristics of the sensor and are converted into a measurement signal.

4. What is the static measurement range?

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

5. What is the dynamic measurement range?

The documented dynamic range is 0–1,000 μm peak-to-peak.

6. What is the sensitivity of the PR6424 sensor?

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

7. What type of equipment can use this sensor?

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

8. Does the sensor connect directly to a PLC?

It is normally used with a compatible signal converter or machinery monitoring interface. The resulting signal may then be connected to suitable monitoring equipment or integrated into a PLC or DCS architecture.

9. What target material is recommended?

The PR6424 family specification identifies ferromagnetic steel, with 42CrMo4 as the standard reference material. Different target materials may require special consideration during calibration.

10. What is the weight of the PR6424/017-021?

The supplied product listing weight is 0.2 kg. Emerson’s family specification gives approximately 200 g for the sensor with a 1 m cable and without armor.

11. Can another PR6424 model replace the PR6424/017-021?

Not automatically. Confirm the complete model suffix, probe dimensions, cable configuration, connector, converter compatibility, and calibration requirements before selecting an alternative.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/017-021, verify the full model number and confirm that the sensor matches the existing machinery monitoring arrangement. The probe diameter alone is not sufficient for identifying a compatible replacement.

Request clear product photographs and check the sensor body, threaded section, cable insulation, connector, and identification label. Confirm whether the unit is supplied with an integrated cable, extension cable, or additional accessories.

For critical machinery applications, ask for relevant product documentation and confirm the compatibility of the probe with the installed signal converter. The complete measurement chain should be checked before commissioning.

During maintenance, inspect the mounting hardware, cable condition, connector, and sensing tip. Keep the sensor installation secure and ensure that the cable is protected from heat, vibration, abrasion, and electromagnetic interference.

If the sensor is replaced, verify the installation gap and calibration according to the manufacturer’s instructions. Compare the new measurement signal with the expected operating range before returning the machinery to normal service.

Conclusion

The Epro PR6424/017-021 16 mm Eddy Current Sensor is designed for non-contact monitoring of shaft vibration, displacement, position, and eccentricity in critical rotating machinery. With a nominal 16 mm sensing head and a supplied listing weight of 0.2 kg, it is intended for use in industrial measurement arrangements involving compatible signal converters and monitoring equipment.

Its PR6424 family specifications include a static measurement range of ±2.0 mm, a dynamic range of 0–1,000 μm, and sensitivity of 4 V/mm. These capabilities make the sensor relevant to turbine, compressor, pump, and fan monitoring applications.

For replacement and maintenance projects, buyers should verify the complete model suffix, cable configuration, connector, target material, and converter compatibility. Correct installation and calibration are essential for reliable machinery condition monitoring.