Product Overview

The EPRO PR6424/011-121 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the condition and operating behavior of rotating machinery. It belongs to the PR6424 sensor family developed for critical turbomachinery applications, including steam turbines, gas turbines, compressors, pumps, and fans.

The sensor uses the eddy current measurement principle to detect changes in the distance between the probe tip and a conductive target surface. During operation, the probe generates an electromagnetic field. Changes in the distance between the sensor and the rotating shaft influence the electrical characteristics of this field. A compatible signal converter processes these changes and produces a measurement signal proportional to shaft displacement.

The PR6424 series is commonly used in machinery protection and condition-monitoring systems. It provides information about shaft vibration, radial and axial displacement, shaft position, eccentricity, and other operating characteristics. These measurements help maintenance personnel identify abnormal mechanical conditions and evaluate the operating stability of critical rotating equipment.

The PR6424/011-121 has a nominal sensor head diameter of 16 mm and a supplied product weight of approximately 0.2 kg. Its compact probe design allows installation near rotating shafts where non-contact measurement is required.

The sensor is generally used together with a compatible EPRO signal converter and monitoring equipment. The complete measurement system depends on the correct combination of probe, cable, converter, and monitoring module. When selecting a replacement, the complete model number and connection configuration should be checked carefully.

Technical Specifications

Note: These are PR6424 family specifications. The exact cable length, connector arrangement, armor configuration, and temperature limits should be confirmed against the complete PR6424/011-121 ordering code and the supplied unit.

Function and Working Principle

The PR6424/011-121 uses eddy current technology to measure the distance between the probe tip and a conductive target. Unlike contact-based measurement devices, the sensor does not need to touch the rotating shaft.

This non-contact measurement method is especially useful in high-speed rotating machinery, where physical contact would create wear and interfere with normal equipment operation.

1. Eddy Current Measurement Principle

The sensor probe produces a high-frequency electromagnetic field. When a conductive metal target approaches the probe, eddy currents are generated in the target surface.

The strength and characteristics of these currents change according to the distance between the probe and the target. The sensor system uses these changes to determine displacement.

A compatible converter processes the probe signal and provides a measurement output that can be interpreted by machinery monitoring equipment.

2. Shaft Displacement Measurement

The sensor can measure changes in the position of a rotating shaft relative to its installed reference point.

In rotating machinery, shaft displacement may occur because of bearing wear, mechanical imbalance, misalignment, thermal expansion, or changing operating loads.

Continuous displacement measurement helps maintenance teams identify changes in machine behavior before they develop into more serious mechanical problems.

3. Shaft Vibration Monitoring

The PR6424 series can be used for radial and axial shaft dynamic displacement measurements.

Radial measurements help identify shaft movement perpendicular to the shaft centerline. Axial measurements monitor movement along the shaft’s longitudinal direction.

These measurements are important for machinery such as turbines and compressors, where abnormal shaft vibration can indicate changes in bearing condition, rotor balance, alignment, or mechanical integrity.

4. Position and Eccentricity Monitoring

The sensor can also measure shaft position and eccentricity.

Eccentricity refers to the deviation of a rotating component from its expected geometric center. Excessive eccentricity may result in uneven mechanical loading, increased vibration, and reduced equipment reliability.

Monitoring this parameter helps engineers evaluate the condition of rotating assemblies and identify mechanical changes during operation.

5. Signal Conversion and Monitoring

The probe is normally connected to a compatible signal converter, such as an appropriate EPRO CON-series unit.

The converter supplies the sensor with the required operating conditions and processes the measurement signal. Its output can then be connected to machinery monitoring equipment or a suitable industrial control system.

The exact converter model must be selected according to the probe configuration and system requirements.

Role in Industrial Control and Machinery Protection Systems

The PR6424/011-121 is a measurement component within a broader machinery monitoring arrangement. It does not independently perform all protection and control functions. Instead, it provides displacement information to compatible signal-processing and monitoring equipment.

Machinery Monitoring Integration

A typical monitoring arrangement includes:

• EPRO PR6424 eddy current sensor.
• Compatible sensor cable and connection hardware.
• EPRO signal converter.
• Machinery protection or monitoring module.
• Control system or plant monitoring platform.

The sensor measures shaft displacement, while the converter processes the signal. The monitoring equipment evaluates the resulting measurement and can provide operating status, alarms, or protection signals according to the configured system.

PLC and DCS Integration

In industrial facilities, machinery monitoring information may be incorporated into a distributed control system or supervisory platform.

The monitoring system can provide measurement values and alarm information to plant operators. This allows equipment condition to be considered alongside process variables such as temperature, pressure, flow, and operating speed.

The exact interface depends on the monitoring module and system architecture. The PR6424 probe itself should not be treated as a direct PLC communication device.

Turbine Protection

Turbines require continuous monitoring because abnormal shaft movement and vibration can affect mechanical reliability.

The PR6424 series can provide displacement measurements used by turbine monitoring systems to evaluate shaft behavior. These measurements may support alarm and trip logic when combined with appropriately configured protection equipment.

Predictive Maintenance

Continuous monitoring data can help maintenance teams identify gradual changes in shaft behavior. By comparing current measurements with historical operating conditions, engineers can investigate possible bearing degradation, alignment changes, imbalance, or other mechanical issues.

The sensor therefore contributes to condition-based maintenance strategies by providing measurement information for machinery diagnostics.

Industrial Applications

The EPRO PR6424/011-121 is intended for applications involving rotating machinery where reliable non-contact shaft measurement is required.

1. Steam Turbines

Steam turbines operate under high mechanical and thermal loads. Their shafts, bearings, and rotor assemblies require continuous condition monitoring.

The PR6424 sensor can measure shaft displacement and vibration-related movement when installed as part of a compatible monitoring system.

These measurements help operators evaluate turbine behavior during startup, normal operation, and changing load conditions.

2. Gas Turbines

Gas turbines are used in power generation and industrial process facilities. Their rotating assemblies operate at high speeds and require accurate machinery monitoring.

Eddy current sensors can provide shaft displacement information for monitoring rotor behavior and supporting machinery protection strategies.

3. Compressors

Industrial compressors are commonly used in chemical processing, oil and gas facilities, refrigeration systems, and other process industries.

Shaft vibration and displacement monitoring can help identify mechanical changes that may affect compressor reliability.

The PR6424 series can be incorporated into a suitable monitoring arrangement to measure these shaft movements.

4. Industrial Pumps

Large industrial pumps operate continuously in many production facilities. Bearing condition, shaft alignment, and rotor stability are important factors in their reliable operation.

Non-contact displacement sensors can provide information about shaft movement and support maintenance activities.

5. Fans and Blowers

Large fans and blowers may experience vibration caused by imbalance, bearing wear, or mechanical misalignment.

When installed in an appropriate monitoring arrangement, the PR6424 sensor can measure shaft displacement and provide data for evaluating rotating equipment behavior.

6. Power Generation Equipment

Power generation facilities rely on turbines, generators, pumps, and auxiliary rotating machinery.

Continuous shaft monitoring can help maintenance teams identify abnormal mechanical conditions and plan inspections before equipment problems lead to unexpected downtime.

Installation and System Integration

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

1. Confirm Mechanical Compatibility

Before installation, verify the sensor head diameter, thread arrangement, probe length, mounting dimensions, and cable configuration.

The supplied sensor head diameter is 16 mm. The probe must be mounted using the correct mechanical arrangement for the specific machine and measurement location.

The target shaft material should also be suitable for the PR6424 measurement system. The manufacturer’s specifications identify ferromagnetic steel as the standard target material.

2. Set the Correct Probe Gap

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

The PR6424 series specifies a nominal center air gap of approximately 2.7 mm. The actual gap should be established according to the applicable sensor and converter documentation.

Incorrect probe positioning can reduce the available measurement range or cause the signal to operate outside its intended linear region.

3. Use a Compatible Signal Converter

The sensor must be paired with a compatible signal converter. The converter should match the sensor series, electrical characteristics, connector configuration, and required output range.

Do not assume that all PR6424 probes can be connected to every converter without checking the system documentation.

4. Cable Routing and Protection

The sensor cable should be routed to minimize mechanical damage and electrical interference.

Avoid excessive bending, sharp edges, high-temperature contact beyond the cable rating, and unnecessary proximity to high-power switching conductors.

The exact cable length and armor configuration for the PR6424/011-121 should be checked against the supplied part and ordering information.

5. Electrical Connection and Grounding

Follow the manufacturer’s wiring instructions when connecting the sensor to its converter.

Check connector condition, cable continuity, grounding arrangements, and signal wiring before commissioning. Poor connections or damaged cable insulation can cause unstable readings or signal loss.

6. Calibration and Commissioning

After installation, verify the sensor gap and check the measurement output across the expected operating range.

Confirm that the monitoring system displays plausible displacement values and that alarm thresholds are configured according to the machinery protection requirements.

Record the installation position, converter configuration, calibration information, and initial operating measurements for future maintenance reference.

Compatible System Components

The PR6424/011-121 is normally used as part of a complete machinery monitoring system.

The components listed above are examples of equipment used in a complete monitoring arrangement. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 series includes different probe configurations. Models may share the same nominal sensor diameter while differing in cable length, armor, probe construction, and connection details.

Before replacing a PR6424/011-121, compare:

• Complete model and ordering code.
• Sensor head diameter and probe length.
• Mounting thread and mechanical arrangement.
• Cable length and cable armor.
• Connector type.
• Sensitivity and linearity.
• Measuring range and nominal air gap.
• Compatible signal converter.
• Monitoring module input requirements.
• Environmental and temperature limits.

A sensor with the same 16 mm head diameter is not necessarily a direct replacement. The complete probe and converter combination must be checked.

Key Advantages

Non-Contact Measurement

The eddy current measurement principle allows the probe to monitor shaft movement without physical contact. This avoids the mechanical wear associated with contact-based measurement methods.

Suitable for Critical Rotating Machinery

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

Shaft Displacement Monitoring

The sensor can provide information about radial and axial shaft displacement, supporting machinery condition assessment.

High Measurement Sensitivity

The series specification lists a sensitivity of 4 V/mm, allowing small changes in the distance between the probe and target to be represented in the measurement signal.

Compact Sensor Design

The 16 mm sensor head supports installation in machinery locations where available mounting space is limited.

Integration with Monitoring Systems

When paired with compatible converters and monitoring modules, the sensor can contribute to continuous machinery monitoring and protection arrangements.

Support for Condition-Based Maintenance

Measurement data can help engineers identify changes in shaft behavior and investigate possible mechanical problems before they lead to equipment failure.

Technical FAQs

1. What is the EPRO PR6424/011-121?

The PR6424/011-121 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and related movement in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm.

3. What is the measuring principle?

It uses eddy current technology. The probe generates an electromagnetic field, and changes in the distance between the probe and a conductive target influence the signal.

4. What is the sensitivity of the PR6424 series?

The published PR6424 series sensitivity is 4 V/mm.

5. What is the measuring range?

The series specification lists a static measuring range of ±2.0 mm and a dynamic measuring range of 0 to 1,000 μm.

6. What material should the sensor target be?

The standard target material identified in the series specification is ferromagnetic steel, with 42CrMo4 used as a reference material.

7. Does the sensor work independently?

No. It is normally used with a compatible signal converter and monitoring equipment. The converter supplies the required operating conditions and processes the sensor signal.

8. Which machines can use this sensor?

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

9. What is the product weight?

The supplied product weight is approximately 0.2 kg. The Emerson PR6424 series specification also lists approximately 200 grams for the sensor with a 1-meter cable and without armor.

10. Can another PR6424 model replace the PR6424/011-121?

Not automatically. Check the complete suffix, probe dimensions, cable length, connector, converter compatibility, and installation requirements before selecting a replacement.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/011-121, verify the complete model number and inspect the sensor’s physical condition. The probe tip, stainless steel sleeve, cable insulation, connector, and mounting thread should be checked for damage.

Cable configuration is particularly important. Different PR6424 variants may have different cable lengths, armor arrangements, and connector details. These characteristics can affect installation and compatibility with the existing monitoring system.

For replacement projects, compare the sensor with the original equipment documentation and confirm that the existing converter supports the selected probe. A mismatch between the probe and converter may result in inaccurate measurements or an unusable signal.

During routine maintenance, inspect the probe mounting, cable routing, connector condition, and signal stability. Check the sensor gap if the machine has been dismantled or the probe mounting position has changed.

Keep records of the initial measurement values and subsequent operating trends. Consistent monitoring helps maintenance teams identify changes in shaft behavior and investigate potential mechanical issues.

Conclusion

The EPRO PR6424/011-121 16 mm Eddy Current Sensor is designed for non-contact shaft displacement monitoring in critical rotating machinery. Based on the PR6424 series specifications, it provides a sensitivity of 4 V/mm, a static measuring range of ±2.0 mm, and a nominal center air gap of approximately 2.7 mm.

With its compact 16 mm probe design, the sensor can be incorporated into machinery monitoring systems for turbines, compressors, pumps, and fans. Correct probe installation, compatible signal conversion, and careful cable configuration are essential for obtaining reliable measurement results.

For industrial maintenance and replacement applications, verifying the complete model code and compatibility with the existing monitoring system is important before ordering.