Product Overview

The Epro PR6424/018-000 16 mm Eddy Current Sensor is a non-contact displacement and vibration measurement probe designed for condition monitoring and machinery protection applications. Part of the Emerson EPRO PR6424 series, this sensor is used to monitor the dynamic behavior and position of rotating shafts 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 requiring physical contact. This makes it suitable for monitoring rotating machinery where continuous measurement is needed without introducing mechanical wear between the sensor and the shaft.

The PR6424 series is designed for applications involving steam turbines, gas turbines, hydro turbines, compressors, pumps, and fans. It can measure radial and axial shaft displacement, shaft position, eccentricity, and rotational speed-related signals when integrated into a compatible monitoring system.

The PR6424 sensor has a nominal sensing-tip diameter of 16 mm and uses an eddy current measurement principle. Its published series 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 that require accurate shaft displacement and vibration measurements.

The PR6424/018-000 is identified as a specific model within this sensor family. Its supplied product information lists a 16 mm sensor head diameter and a weight of approximately 0.2 kg. Exact cable length, connector arrangement, and cable protection should be checked against the physical product label and ordering documentation because these details can vary between PR6424 configurations.

Technical Specifications

Note: These are PR6424 series specifications. Confirm the exact /018-000 cable, connector, temperature, and installation configuration before selecting or replacing the sensor.

Function and Working Principle

The PR6424/018-000 operates using the eddy current principle. It generates a high-frequency 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 close to a conductive shaft surface without touching it. When the distance between the probe tip and the shaft changes, the electromagnetic interaction also changes.

The sensor system uses this change to determine the relative position of the shaft. This allows the monitoring equipment to detect shaft movement without mechanical contact between the probe and the rotating component.

Non-contact measurement is particularly useful in high-speed machinery, where direct contact would cause wear and could interfere with normal equipment operation.

2. Eddy Current Measurement Principle

An alternating electromagnetic field is generated by the probe coil. When a conductive target enters this field, eddy currents are induced in the target surface.

These currents affect the impedance of the probe coil. The resulting electrical change is related to the distance between the probe and the target.

A compatible signal converter processes the sensor response and produces a usable measurement signal. The resulting signal can then be supplied to a machinery protection or condition-monitoring system.

3. Shaft Vibration Monitoring

As a rotating shaft vibrates, its distance from the stationary sensor changes. The probe detects this movement and provides a signal that represents shaft displacement.

When installed in suitable pairs and configured correctly, eddy current probes can support measurements of radial shaft vibration and other dynamic shaft movements.

This information helps maintenance engineers identify abnormal vibration patterns, changes in machine behavior, and potential mechanical problems.

4. Shaft Position and Eccentricity Measurement

The PR6424 series can also be used for static shaft-position measurements. These measurements are useful for evaluating shaft position relative to the machine housing or bearing structure.

Eccentricity monitoring can help identify shaft movement or geometric conditions that may affect machinery operation. The measurement range and installation geometry must be considered when interpreting these signals.

5. Speed and Keyphasor-Related Measurement

A suitable probe arrangement can detect shaft-related features and generate signals used for rotational speed or phase-reference measurements.

These signals may be used by a machinery monitoring system to calculate rotational speed, synchronize vibration measurements, and analyze machine behavior.

The actual speed or phase-reference function depends on the target geometry, probe installation, and compatible monitoring equipment.

Role in Industrial Machinery Protection Systems

The PR6424/018-000 is designed to function as a sensing element within a broader machinery monitoring system. It does not normally operate as a standalone PLC input device without appropriate signal conditioning.

1. Integration with Signal Converters

An eddy current probe requires a compatible converter or signal-conditioning unit to process its electrical response.

The converter provides the required excitation and converts the probe response into a signal suitable for machinery monitoring equipment.

The sensor, extension cable where applicable, and converter must be compatible as a measurement chain. Mixing components from different configurations without checking electrical and calibration requirements may lead to inaccurate measurements.

2. Integration with Machinery Protection Systems

A machinery protection system receives measurement signals from installed probes and evaluates operating conditions.

Depending on the monitoring architecture, the system can process shaft vibration, axial position, eccentricity, and rotational speed information.

When measured values exceed configured limits, the protection system may generate alarms or initiate protective actions through the plant control architecture.

3. Integration with DCS and PLC Systems

A distributed control system or PLC may receive status information from the machinery monitoring system. Operators can then view machine condition information alongside process variables such as temperature, pressure, flow, and motor status.

The sensor itself should be treated as part of the measurement chain. Its compatibility with the converter and monitoring hardware must be established before planning DCS or PLC integration.

4. Continuous Condition Monitoring

Continuous shaft monitoring provides information about equipment behavior during operation. Maintenance personnel can compare current measurements with historical operating data to identify changes that may indicate developing mechanical problems.

This approach supports condition-based maintenance and can help maintenance teams investigate abnormal machine behavior before it develops into a major equipment failure.

Industrial Applications

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

1. Steam Turbines

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

Eddy current probes can measure relative shaft displacement and provide information for machinery protection systems. Monitoring these values helps operators identify abnormal shaft movement and evaluate changes in turbine operating conditions.

2. Gas Turbines

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

The PR6424 sensor family can be used in suitable turbine monitoring arrangements to measure shaft displacement, vibration, and position.

Correct probe placement and temperature compatibility are important when selecting sensors for these applications.

3. Hydro Turbines

Hydro turbines may experience shaft movement associated with hydraulic forces, bearing conditions, and operating load changes.

Non-contact displacement sensors can provide information about shaft vibration and relative position. This information supports equipment condition assessment and maintenance planning.

4. Industrial Compressors

Large compressors are widely used in petrochemical plants, refineries, gas-processing facilities, and manufacturing operations.

Shaft vibration and position monitoring can help maintenance teams evaluate bearing performance, rotor behavior, and changes in mechanical condition.

The PR6424 series is intended for suitable compressor applications where its measurement range and installation requirements match the equipment design.

5. Industrial Pumps

Critical pumps may operate continuously in water treatment, chemical processing, power generation, and oil and gas facilities.

Monitoring shaft displacement and vibration can help identify mechanical changes associated with bearing wear, rotor imbalance, misalignment, or other abnormal operating conditions.

6. Industrial Fans

Large fans used in power plants and process industries can experience vibration due to imbalance, mechanical looseness, or bearing problems.

A suitable monitoring arrangement can use displacement measurements to support machinery condition assessment and maintenance decisions.

Installation and System Integration

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

1. Confirm the Sensor Configuration

Before installation, verify the complete model number, sensor cable arrangement, connector type, and compatible converter.

The PR6424 family contains different configurations. The suffix /018-000 should be checked against the actual product documentation to confirm its specific cable and connection details.

Do not assume that all PR6424 probes have identical cable lengths or connector arrangements.

2. Select the Correct Mounting Position

The probe should be installed at the location specified by the machinery manufacturer or monitoring-system design.

The sensor tip must face the intended conductive target surface. The mounting position should provide adequate clearance and prevent accidental contact with the rotating shaft.

For shaft vibration measurement, probe orientation and mounting rigidity are important. Loose mounting hardware can introduce measurement errors or unstable signals.

3. Set the Initial Air Gap

The PR6424 series has a nominal center air gap of approximately 2.7 mm in the documented standard configuration.

The actual installation gap must follow the applicable converter and sensor instructions. Correct gap adjustment is necessary to keep the measurement within the intended linear operating range.

An incorrect gap can reduce measurement accuracy or cause the sensor output to operate outside its specified range.

4. Check the Target Material

The published PR6424 specifications use ferromagnetic steel, with 42CrMo4 as the standard target material.

The electrical characteristics of the target surface affect sensor calibration. If the shaft material differs from the standard material, the measurement chain may require specific calibration or engineering review.

5. Route the Sensor Cable Correctly

The cable should be routed away from high-voltage power conductors, variable frequency drive output cables, and other strong electromagnetic interference sources where practical.

Avoid excessive bending, crushing, pulling, or twisting. Maintain the minimum bending radius specified for the actual cable configuration.

Cable protection and routing should be suitable for the machinery environment, including temperature, vibration, oil exposure, and mechanical movement.

6. Connect the Compatible Signal Converter

Connect the sensor to the specified converter using the correct cable and connector arrangement.

Verify the converter model, power requirements, calibration, and output configuration. The complete measurement chain should be checked before connecting its output to a machinery protection system.

7. Commission and Verify Measurements

After installation, verify the sensor gap, cable continuity, converter operation, and output signal.

Compare the measured values with expected machine conditions and confirm that the monitoring system is configured with appropriate alarm and trip limits.

Record the installation position, calibration details, and measurement settings for future maintenance.

Compatible System Components

The PR6424/018-000 is normally used with compatible signal-conditioning and machinery-monitoring equipment.

The sensor, extension cable, converter, and monitoring system should be treated as one measurement chain. Confirm the complete configuration before purchasing individual replacement components.

Alternative Models and Replacement Considerations

The PR6424 belongs to the EPRO PR642x family of eddy current sensors. Other models may have different probe diameters, measuring ranges, sensitivities, and application limits.

Before replacing the PR6424/018-000, compare:

• Complete model and suffix.
• Sensor head diameter.
• Thread and mounting arrangement.
• Cable length and connector type.
• Cable armor and temperature rating.
• Sensitivity and measurement range.
• Compatible converter.
• Target material and calibration.
• Environmental and certification requirements.

A sensor from the same product family is not automatically a direct replacement. Differences in cable configuration, converter compatibility, or calibration can affect the complete measurement system.

Key Advantages

Non-Contact Measurement

The eddy current principle measures shaft movement without physical contact, reducing mechanical wear between the probe and the rotating target.

Suitable for Critical Rotating Machinery

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

Shaft Vibration and Position Monitoring

The sensor can support both static shaft-position measurements and dynamic displacement measurements when used in a compatible system.

High Measurement Sensitivity

The documented series sensitivity of 4 V/mm supports accurate displacement measurement within the specified linear operating range.

Compact 16 mm Sensor Head

The 16 mm sensing head is suitable for machinery installations designed around this probe size.

Industrial Operating Capability

The documented PR6424 configuration supports demanding machinery environments, subject to its specified temperature, pressure, vibration, and cable limits.

Integration with Machinery Monitoring Systems

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

Technical FAQs

1. What is the Epro PR6424/018-000?

The Epro PR6424/018-000 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement, vibration, and position in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm.

3. What is the measurement principle?

It uses the eddy current principle. Changes in the distance between the probe and a conductive target affect the probe’s electromagnetic response, allowing the system to determine shaft displacement.

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

The documented standard series specifications include a static measurement range of ±2.0 mm and a dynamic measurement range of 0 to 1,000 μm.

5. What is the sensitivity of the sensor?

The published PR6424 series sensitivity is 4 V/mm, with linearity of up to ±1.5% under the specified standard conditions.

6. What is the nominal air gap?

The documented nominal center air gap is approximately 2.7 mm. The final installation gap must follow the applicable sensor and converter instructions.

7. Which machines can use this sensor?

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

8. Does the sensor connect directly to a PLC?

The sensor normally requires a compatible signal converter or conditioning unit. The conditioned output can then be connected to an appropriate machinery monitoring system or control-system interface.

9. What is the weight of the PR6424/018-000?

The supplied product information lists a weight of approximately 0.2 kg. Emerson’s PR6424 series specification sheet gives approximately 200 grams for the sensor with a 1-meter cable without armor. The exact weight depends on the cable and protection configuration.

10. Can another PR6424 model replace the /018-000?

Not automatically. The complete suffix, cable length, connector, mounting arrangement, and converter compatibility should be checked before replacement.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/018-000, verify the complete model number and compare it with the identification marking on the existing sensor. Check the sensor head diameter, mounting thread, cable arrangement, connector, and any protective armor.

For used or refurbished units, request clear photographs of the probe tip, mounting body, cable, connector, and model label. Inspect the cable for cuts, crushing, heat damage, or signs of previous repairs.

For critical machinery, confirm that the replacement sensor is compatible with the existing signal converter. A probe with a similar diameter may still have different electrical or mechanical characteristics.

During maintenance, inspect the mounting position, cable routing, connector condition, and sensor gap. Avoid bending or pulling the cable beyond its specified limits. If the measurement becomes unstable, check the probe gap, cable connections, converter compatibility, grounding, and target surface condition.

Keep records of sensor installation locations, converter settings, calibration information, and machinery monitoring limits. These records help maintenance personnel identify configuration changes and improve troubleshooting efficiency.

Conclusion

The Epro PR6424/018-000 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement, vibration, and position in critical rotating machinery. Its compact sensing head and the PR6424 series’ documented 4 V/mm sensitivity and ±2.0 mm static measurement range make it suitable for compatible machinery protection and condition-monitoring systems.

For reliable operation, the sensor must be matched with the correct cable, signal converter, target material, and monitoring equipment. Confirming the complete /018-000 configuration before installation or replacement is essential for maintaining measurement accuracy and system compatibility.