Product Overview

The Epro PR6424/018-100 16mm Eddy Current Sensor is a non-contact displacement and vibration measurement probe designed for monitoring critical rotating machinery. Manufactured under the EPRO product line associated with Emerson, the PR6424 series is widely used in machinery condition monitoring and protection systems.

The sensor operates using eddy current measurement technology. It detects changes in the distance between the probe tip and a conductive target, such as a rotating steel shaft. These changes are converted into electrical signals by a compatible signal converter, allowing monitoring equipment to evaluate shaft displacement, vibration, axial position, eccentricity, and rotational speed-related signals.

With a nominal sensor head diameter of 16 mm, the PR6424 series is designed for applications involving relatively large rotating shafts. Typical equipment includes steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans.

The PR6424/018-100 belongs to the PR6424 16 mm sensor family. Its family-level specifications include a sensitivity of 4 V/mm, a static measurement range of ±2.0 mm, and a dynamic measurement range of 0 to 1,000 μm. These characteristics make it suitable for machinery monitoring applications where accurate non-contact measurement is important.

The sensor is generally used as part of a complete measurement chain that includes a probe, extension cable, and compatible signal converter or monitoring module. Correct matching and calibration of these components are essential for reliable measurements.

Technical Specifications

Note: These are PR6424 family-level specifications and the user-provided listing values. Exact cable length, connector, probe construction, and other suffix-specific details should be verified against the PR6424/018-100 product label or ordering documentation.

Function and Working Principle

The PR6424/018-100 uses eddy current technology to measure the distance between the sensor probe and a conductive target without direct mechanical contact.

This measurement principle is particularly useful for rotating machinery because it allows shaft movement to be monitored while the equipment is operating.

1. Eddy Current Measurement Principle

The probe contains an electromagnetic sensing coil. When the sensor is supplied with the appropriate high-frequency excitation from a compatible converter, an electromagnetic field develops around its sensing tip.

When a conductive metallic target approaches the probe, eddy currents are induced in the target surface. These currents affect the electromagnetic characteristics of the sensing coil.

The resulting change in electrical impedance is related to the distance between the sensor and the target.

A compatible signal converter processes this response and produces a measurement signal that can be interpreted by a machinery monitoring system.

2. Shaft Displacement Measurement

The sensor can monitor changes in the distance between the probe and a rotating shaft.

This allows engineers to identify changes in shaft position caused by mechanical movement, bearing conditions, thermal expansion, or other operating influences.

The PR6424 series has a static measurement range of approximately ±2.0 mm. This provides a measurement capability for monitoring shaft position within the specified operating range.

3. Shaft Vibration Monitoring

Rotating machinery may experience vibration due to imbalance, misalignment, bearing wear, looseness, or changing operating conditions.

When the sensor is installed near a rotating shaft, it can detect small changes in the shaft-to-probe gap. These measurements can be used to evaluate radial shaft vibration.

The PR6424 family supports dynamic measurement from 0 to 1,000 μm, making it suitable for machinery vibration monitoring when correctly installed and calibrated.

4. Axial Position Monitoring

Axial shaft movement is another important parameter in turbine and compressor protection.

The sensor can be installed in an appropriate position to measure changes in the shaft’s axial location. Monitoring this movement helps engineers identify abnormal displacement that may be associated with thrust-bearing conditions or other mechanical problems.

The measurement arrangement must be designed around the machine’s mechanical geometry and the monitoring system’s requirements.

5. Speed and Key-Related Measurement

With suitable target geometry and signal-processing equipment, an eddy current sensor can also provide information related to rotational speed or reference positions.

This can support machinery monitoring functions such as rotational-speed measurement and keyphasor-related analysis. The specific capability depends on the probe installation, target arrangement, converter, and monitoring equipment.

Role in Industrial Machinery Monitoring Systems

The PR6424/018-100 is typically used as a sensing component within a larger machinery protection and condition-monitoring system.

It does not normally operate as a standalone measurement instrument. Instead, it works with compatible signal-conditioning equipment and monitoring modules.

1. Connection to Signal Converters

The sensor must be paired with a compatible EPRO signal converter or measurement system.

Depending on the system configuration, compatible equipment may include converter models such as CON011, CON021, CON031, or CON041. The correct combination must be confirmed from the manufacturer’s compatibility documentation.

The converter supplies the required excitation and processes the sensor response into a usable output signal.

2. Integration with Machinery Monitoring Modules

The conditioned measurement signal can be connected to a machinery monitoring system.

Monitoring equipment can evaluate the sensor signal and provide information about shaft vibration, position, and other configured parameters.

In a larger installation, the monitoring system may communicate with a DCS, PLC, or plant supervisory system.

3. Alarm and Protection Functions

Machinery protection systems use measurement signals to identify abnormal operating conditions.

For example, excessive shaft vibration or abnormal axial displacement may indicate a mechanical problem that requires inspection.

When configured with suitable alarm and trip thresholds, the monitoring system can provide warnings or initiate protective actions according to the plant’s operating philosophy.

The sensor itself measures displacement; alarm logic and protective actions are handled by the connected monitoring and control equipment.

4. Condition-Based Maintenance

Continuous measurement data can help maintenance teams evaluate machinery performance over time.

By comparing current measurements with historical trends, engineers may identify gradual changes that are not immediately apparent during routine inspections.

This information can support condition-based maintenance and help maintenance teams plan inspections according to actual equipment conditions.

Industrial Applications

The Epro PR6424 series is designed for critical rotating machinery where non-contact displacement measurement is required.

1. Steam Turbines

Steam turbines operate at high rotational speeds and require continuous monitoring of shaft vibration and position.

The PR6424 sensor can be installed near suitable shaft measurement locations to detect radial displacement and support machinery protection functions.

Typical monitoring applications include:

• Radial shaft vibration.
• Shaft position.
• Axial displacement.
• Shaft eccentricity.
• Rotational reference measurements.

Reliable installation and correct converter calibration are important for accurate measurements.

2. Gas Turbines

Gas turbines are used in power generation and industrial process applications. Their rotating assemblies operate under demanding mechanical and thermal conditions.

The PR6424 sensor can support shaft vibration and displacement monitoring as part of a compatible machinery protection system.

Measurement trends can help engineers identify abnormal mechanical behavior and investigate changes in operating conditions.

3. Hydro Turbines

Hydroelectric generating equipment contains large rotating shafts and bearing systems that require continuous monitoring.

The 16 mm sensor design is suitable for applications involving relatively large shaft diameters. It can be used to monitor shaft movement and vibration when the installation meets the required mechanical and electrical specifications.

4. Industrial Compressors

Centrifugal and other large industrial compressors depend on stable shaft operation.

Excessive vibration, displacement, or changes in shaft position may indicate mechanical problems.

The PR6424 series can provide non-contact measurements that support compressor protection and condition monitoring.

5. Industrial Pumps

Large process pumps and power-generation pumps may require continuous monitoring of shaft vibration and position.

The sensor can be installed at suitable measurement points to provide information about shaft movement and mechanical operating conditions.

6. Industrial Fans

Large industrial fans and ventilation systems may use shaft vibration monitoring to help identify imbalance, bearing deterioration, and other mechanical issues.

The PR6424 can be used where its measurement range and installation requirements are appropriate for the equipment.

Installation and System Integration

Correct sensor installation is essential for accurate measurement and reliable machinery monitoring.

1. Confirm Sensor and Converter Compatibility

Before installation, verify that the PR6424/018-100 is compatible with the intended signal converter.

Check the complete sensor model, cable arrangement, connector type, and converter configuration. A probe with a similar diameter may not have the same electrical characteristics or calibration requirements.

Do not assume that every PR6424 variant can be connected to every converter without checking the manufacturer’s documentation.

2. Select the Correct Measurement Position

The probe should be mounted at a location that provides a stable measurement surface and appropriate clearance from the rotating shaft.

For shaft vibration measurement, the installation position should be selected according to the machinery manufacturer’s recommendations and the monitoring system’s design.

Avoid locations where the probe may be exposed to mechanical impact or excessive interference from nearby ferromagnetic structures.

3. Set the Initial Air Gap

The nominal center air gap for the PR6424 family is approximately 2.7 mm.

The actual installation gap must be established using the appropriate calibration procedure and compatible converter.

Incorrect probe spacing may reduce measurement accuracy or cause the sensor to operate outside its linear measurement range.

4. Check the Target Material

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

Target material differences can influence the measurement response. Engineers should verify the shaft material and calibration requirements before commissioning.

5. Route and Protect the Sensor Cable

The sensor cable should be routed away from high-voltage power conductors and strong electromagnetic interference sources where possible.

Avoid excessive bending, pulling, twisting, or mechanical stress. Follow the applicable cable bending-radius requirements and installation instructions for the exact cable construction.

Cable extensions and connectors must be compatible with the selected measurement chain.

6. Verify Measurement Signals

After installation, check the complete measurement chain, including the probe, cable, converter, and monitoring module.

Confirm that the output responds correctly to changes in probe-to-target distance and that the configured measurement range matches the application.

Record the installation gap and calibration information for future maintenance.

Compatible System Components

A complete PR6424 measurement system typically includes a probe, suitable cable arrangement, signal converter, and machinery monitoring equipment.

The components listed are examples of equipment used in PR6424 measurement systems. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 series includes different probe configurations and cable arrangements. Replacement selection should be based on the complete model number rather than the 16 mm diameter alone.

Before replacing the PR6424/018-100, compare:

• Sensor head diameter.
• Probe body length.
• Thread size and mounting arrangement.
• Cable length and construction.
• Connector type.
• Measurement range.
• Sensitivity and linearity.
• Target material and calibration.
• Operating temperature.
• Signal converter compatibility.

A replacement probe with the same 16 mm diameter may still be unsuitable if its cable, calibration, or electrical characteristics differ.

Key Advantages

Non-Contact Measurement

The sensor measures shaft movement without physical contact, avoiding the mechanical wear associated with contact-based measurement methods.

High Measurement Sensitivity

The PR6424 family provides a nominal sensitivity of 4 V/mm, supporting measurement of relatively small changes in the probe-to-target distance.

Static and Dynamic Measurement

The sensor supports both static position measurement and dynamic displacement measurement, making it useful for different machinery monitoring functions.

Suitable for Large Rotating Machinery

The 16 mm probe design is intended for applications involving relatively large shafts, including turbines and industrial compressors.

Industrial Temperature Capability

The family-level operating temperature range of -35°C to +180°C supports installation in demanding machinery environments when all installation limits are respected.

Integration with Machinery Protection Systems

When paired with a compatible converter and monitoring module, the sensor can provide measurement signals for machinery condition monitoring and protection.

Support for Predictive Maintenance

Continuous shaft measurement data can help maintenance teams identify abnormal trends and plan inspections before mechanical conditions become more serious.

Technical FAQs

1. What is the Epro PR6424/018-100?

It 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 specified sensor head diameter is 16 mm.

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

The family-level static measurement range is approximately ±2.0 mm, while the dynamic measurement range is 0 to 1,000 μm.

4. What is the sensitivity of the PR6424 sensor?

The nominal sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil, with a specified linearity of up to ±1.5%.

5. What is the typical operating temperature?

The PR6424 family has a published operating temperature range of approximately -35°C to +180°C. Confirm the exact limits for the installed probe and cable configuration.

6. What equipment can the sensor monitor?

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

7. Does the PR6424/018-100 operate independently?

No. It normally requires a compatible signal converter and monitoring equipment to provide usable measurement signals.

8. What target material is used for calibration?

The standard reference target material is ferromagnetic steel, commonly specified as 42CrMo4. Different target materials may affect measurement performance.

9. What is the weight of the sensor?

The supplied product listing weight is 0.2 kg. Emerson’s family specification also gives an approximate weight of 200 grams for the sensor with a 1 m cable and without armor. Actual weight can vary with cable and connector configuration.

10. Can another PR6424 model replace the PR6424/018-100?

Not automatically. The complete model number, probe length, mounting thread, cable arrangement, connector, and converter compatibility should be checked before substitution.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/018-100, verify the complete model number on the product label. Confirm the sensor head diameter, cable configuration, connector type, probe length, and physical condition.

For used or surplus sensors, request clear photographs of the probe, cable, connector, and identification label. Check for damaged insulation, bent mounting components, corrosion, or signs of mechanical impact.

For critical machinery applications, request suitable electrical testing or calibration information where available. Confirm compatibility with the existing signal converter before ordering a replacement.

During maintenance, inspect the sensor mounting arrangement and cable condition. Ensure that the probe remains securely installed and that the measurement gap is within the specified operating range.

Maintain records of probe replacement, calibration, installation position, and measurement settings. These records can help engineers identify changes in measurement performance and simplify future troubleshooting.

Conclusion

The Epro PR6424/018-100 16mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in critical rotating machinery. With a 16 mm sensor head and PR6424 family characteristics including 4 V/mm sensitivity, a ±2.0 mm static measurement range, and a 0 to 1,000 μm dynamic measurement range, it can support machinery condition monitoring in turbines, compressors, pumps, and industrial fans.

For reliable operation, the sensor must be matched with a compatible signal converter, cable arrangement, and monitoring system. When purchasing or replacing the PR6424/018-100, checking the complete model suffix and connection configuration is essential for maintaining measurement accuracy and system compatibility.