Product Overview

The EPRO PR6424/102-121 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the operating condition of rotating machinery. It belongs to the PR6424 sensor family, which is used in machinery protection and condition monitoring applications involving steam turbines, gas turbines, compressors, pumps, and industrial fans.

The sensor operates using the eddy current measurement principle. Instead of physically contacting a rotating shaft, it generates an electromagnetic field and detects changes in that field caused by the position of a conductive target. These changes can be converted into measurement signals representing shaft displacement and movement.

In industrial machinery, shaft vibration and displacement are important indicators of mechanical condition. Excessive vibration, abnormal shaft movement, or changes in axial position may indicate bearing wear, rotor imbalance, misalignment, looseness, or other developing mechanical problems. A suitable monitoring system can use sensor measurements to help operators identify these conditions and take corrective action.

The PR6424 series uses a 16 mm sensor head and is designed for demanding machinery monitoring environments. Its measurement characteristics include a nominal center air gap of approximately 2.7 mm, sensitivity of 4 V/mm, and linearity of up to ±1.5% under specified conditions.

The PR6424/102-121 is intended to be used with compatible signal-conditioning electronics and machinery monitoring equipment. The sensor probe alone does not provide a complete monitoring or protection function. Correct operation depends on the matching converter, extension cable where applicable, mounting arrangement, target material, and system calibration.

The supplied product information identifies the sensor head diameter as 16 mm and the weight as 0.2 kg. These values are consistent with the general PR6424 family specification. Exact cable length, connector configuration, mounting dimensions, and other suffix-specific details should be checked against the product label and applicable ordering documentation before replacement.

Technical Specifications

Note: The technical performance values above are based on published PR6424 family specifications. Confirm the exact /102-121 cable, connector, thread, temperature rating, and mounting details before installation.

Function and Working Principle

The PR6424/102-121 uses electromagnetic induction to measure the distance between the sensor tip and a conductive target. In typical machinery monitoring applications, the target is a rotating shaft made from a suitable ferromagnetic material.

1. Eddy Current Measurement Principle

An alternating electrical signal supplied by compatible driver electronics creates an electromagnetic field around the sensor coil.

When a conductive metal target is positioned near the sensor, eddy currents are induced in the target surface. These currents affect the electromagnetic field and change the electrical characteristics of the sensor circuit.

The signal-conditioning electronics evaluate this change and convert it into an output related to the distance between the probe and the target.

This measurement method allows the sensor to monitor shaft movement without requiring physical contact. It is therefore suitable for rotating equipment where mechanical contact would cause wear or interfere with operation.

2. Shaft Displacement Measurement

The sensor can measure changes in the distance between its tip and the shaft surface. When installed near a rotating shaft, it detects movement relative to the fixed mounting position.

This information can be used to monitor radial shaft displacement and other mechanical movements, depending on the probe orientation and monitoring-system configuration.

The published PR6424 family static measuring range is ±2.0 mm. This range describes the specified measurement capability around the reference position, not an unrestricted installation clearance.

3. Dynamic Vibration Monitoring

A rotating shaft does not always remain in a perfectly fixed position. Its movement may vary during each revolution due to imbalance, misalignment, bearing conditions, or changing operating loads.

The PR6424 sensor detects these dynamic changes. When paired with compatible monitoring electronics, the measurement signal can be used to analyze shaft vibration and identify changes in machine behavior.

The published dynamic measuring range for the standard PR6424 configuration is 0–1,000 μm.

4. Position and Eccentricity Monitoring

The sensor can also support shaft-position and eccentricity measurements. Eccentricity describes the difference between the geometric center of a shaft and its actual rotational behavior.

In turbine and compressor installations, eccentricity information can help operators assess rotor movement during startup, shutdown, and normal operation.

The usefulness of this measurement depends on sensor placement, calibration, shaft surface condition, and the monitoring system’s configuration.

5. Signal Conversion and Monitoring

The probe must be paired with compatible signal-conditioning electronics. The converter supplies the appropriate excitation and processes the sensor response into a usable measurement signal.

A monitoring rack or machinery protection system can then use this signal for display, alarm generation, trend analysis, and protective logic.

The complete system must be configured for the correct sensor family and measurement range. A sensor should not be connected to an arbitrary converter simply because the connector appears similar.

Role in Industrial Machinery Monitoring Systems

The EPRO PR6424/102-121 is designed to function as a measurement component within a larger machinery monitoring arrangement.

Turbine Shaft Monitoring

Steam and gas turbines contain high-speed rotating assemblies that require continuous condition monitoring. Shaft vibration and displacement measurements help operators evaluate rotor behavior under different operating conditions.

A suitable PR6424 installation can provide non-contact shaft measurements for a compatible turbine monitoring system.

Compressor Condition Monitoring

Industrial compressors operate under changing process loads and demanding mechanical conditions. Shaft movement may be influenced by rotor imbalance, bearing wear, coupling problems, or changes in operating conditions.

A non-contact displacement probe can provide measurement information used by maintenance teams to assess compressor condition.

Pump Monitoring

Large industrial pumps are often installed in continuous-process facilities. Abnormal shaft movement may indicate mechanical problems that require inspection.

The PR6424 family can be used in compatible pump monitoring arrangements to measure shaft displacement and vibration.

Integration with Machinery Protection Systems

The sensor can provide measurement signals to compatible signal converters and machinery monitoring modules. Depending on the monitoring architecture, these signals may be used for:

• Continuous shaft displacement measurement.
• Vibration trend analysis.
• Operating-condition monitoring.
• Alarm and trip logic.
• Maintenance diagnostics.
• Machinery performance evaluation.

The sensor itself does not independently generate all alarms or perform machinery shutdown functions. Those functions depend on the connected monitoring and protection equipment.

Industrial Applications

1. Steam Turbines

Steam turbines operate at high rotational speeds and are commonly used in power generation and industrial process facilities.

Shaft vibration and displacement measurements are important for evaluating rotor condition. A compatible PR6424 sensor installation can provide non-contact measurements for monitoring turbine shaft movement.

2. Gas Turbines

Gas turbines operate under high temperatures, substantial mechanical loads, and demanding operating cycles.

Machinery monitoring systems use shaft displacement and vibration information to evaluate rotating assembly behavior. Sensor selection and installation must account for the specific operating environment and the exact probe temperature rating.

3. Industrial Compressors

Centrifugal and other high-speed compressors require reliable monitoring of rotating components. Changes in shaft vibration may indicate developing mechanical issues.

The PR6424 family is suitable for compatible compressor monitoring arrangements where the measurement range and installation geometry meet the application requirements.

4. Industrial Pumps

Pumps used in power generation, chemical processing, petrochemical facilities, and water treatment plants may operate continuously for long periods.

Non-contact shaft measurement can help maintenance teams monitor mechanical movement without introducing physical contact with the rotating shaft.

5. Industrial Fans and Blowers

Large fans and blowers are used in ventilation, combustion air supply, cooling, and process exhaust systems.

A suitable displacement sensor can support monitoring of rotating shafts and help identify changes in mechanical behavior.

6. Power Generation Facilities

Power plants rely on rotating machinery that must operate within defined mechanical limits. Turbines, generators, pumps, and auxiliary equipment may be included in centralized condition monitoring systems.

The PR6424 family can be used as part of an appropriately designed monitoring arrangement where the probe and signal-conditioning equipment are compatible.

Installation and System Integration

Correct installation is essential for reliable measurement. Sensor position, target material, mounting rigidity, electrical compatibility, and cable routing all influence performance.

1. Verify the Exact Sensor Configuration

Before installation, check the complete model number, including the /102-121 suffix. Confirm the cable arrangement, connector, thread, mounting dimensions, and applicable temperature rating.

Different PR6424 ordering variants may have different cable lengths, connector arrangements, and mechanical configurations. A replacement should not be selected based only on the 16 mm probe diameter.

2. Confirm Compatibility with Signal Conditioning Electronics

The PR6424 sensor requires compatible driver or signal-converter electronics.

The signal conditioner must match the sensor type and measurement range. Check the approved system configuration before connecting the probe.

Incorrect matching may result in inaccurate readings, unstable output, or an unusable measurement signal.

3. Maintain the Correct Installation Gap

The published PR6424 family specification gives a nominal center air gap of approximately 2.7 mm.

The actual installation gap must follow the manufacturer’s setup procedure and the requirements of the matching signal conditioner. It should not be estimated from the sensor’s physical appearance.

An incorrect gap can reduce measurement accuracy or move the probe outside its linear operating range.

4. Check the Shaft Target Material

The PR6424 family is designed for measurement against a suitable ferromagnetic target. The published standard reference material is 42CrMo4 steel.

The shaft surface and material should be checked before installation. Material differences, surface conditions, and target geometry can affect the measurement response.

5. Secure the Sensor Mounting

The probe should be installed using a rigid mounting arrangement that prevents unwanted movement.

Loose mounting can introduce measurement errors because the sensor may move relative to the machine structure. The mounting location should also provide suitable access for inspection and maintenance.

6. Protect the Cable and Connector

The cable should be routed away from hot surfaces, moving components, sharp edges, and sources of mechanical damage.

Observe the minimum bending radius and connector handling requirements for the exact cable configuration. Avoid pulling directly on the cable when connecting or disconnecting the sensor.

7. Perform System Calibration

After installation, follow the signal conditioner manufacturer’s calibration procedure. Confirm the initial gap, output response, polarity, and measurement scaling.

Where the sensor forms part of a machinery protection system, verify alarm and trip settings through the approved commissioning procedure.

8. Verify the Measurement Signal

Before returning the machine to service, check that the monitoring system receives a stable signal and that the measured values are consistent with the expected mechanical condition.

Record the installation gap, sensor position, calibration information, and relevant system parameters for future maintenance.

Compatible System Components

The PR6424/102-121 is part of a measurement chain rather than a standalone machinery protection system. The following components may be used in a compatible installation.

The listed components are examples of equipment used in compatible monitoring architectures. They are not necessarily supplied with the sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to a wider EPRO eddy current sensor family. Other models may share the same general measurement principle but can differ in probe diameter, measurement range, mechanical construction, cable arrangement, and installation requirements.

When replacing a PR6424/102-121, compare the following:

• Complete sensor model and suffix.
• Probe head diameter and mechanical dimensions.
• Thread and mounting arrangement.
• Cable length and cable construction.
• Connector type and pin arrangement.
• Operating temperature rating.
• Matching signal converter.
• Measurement range and sensitivity.
• Target material and shaft geometry.
• Monitoring system input configuration.

A sensor with the same 16 mm head diameter is not necessarily a direct replacement. The complete electrical and mechanical configuration must be checked.

Key Advantages

Non-Contact Measurement

The eddy current principle allows shaft displacement to be measured without physical contact between the sensor and the rotating target. This avoids the mechanical wear associated with contact-based measurement.

Suitable for Critical Rotating Machinery

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

High Measurement Sensitivity

The published family sensitivity is 4 V/mm, supporting the detection of relatively small changes in the distance between the probe and the target.

Defined Linear Measuring Range

The standard family specification provides a static measuring range of ±2.0 mm and a dynamic range of 0–1,000 μm.

Industrial Construction

The PR6424 family uses a stainless steel probe sleeve and PTFE cable material, supporting use in demanding industrial monitoring installations within the specified environmental limits.

Integration with Machinery Monitoring Systems

When paired with compatible signal-conditioning electronics, the sensor can supply measurement information for machinery diagnostics, trend analysis, and protection functions.

Low Sensor Weight

The supplied weight of 0.2 kg is consistent with the published approximate weight of a PR6424 sensor with a 1-meter cable and without armor.

Technical FAQs

1. What is the EPRO PR6424/102-121?

The EPRO PR6424/102-121 is a 16 mm eddy current displacement sensor designed for non-contact measurement of shaft movement in rotating machinery.

2. What is the main function of this sensor?

Its primary function is to measure the distance between the sensor tip and a conductive target. In machinery monitoring systems, this measurement can be used to evaluate shaft displacement, vibration, position, and eccentricity.

3. What is the sensor head diameter?

The sensor head diameter is 16 mm, consistent with the PR6424 family designation.

4. What is the sensitivity of the PR6424 sensor?

The published PR6424 family sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil.

5. What is the static measuring range?

The standard PR6424 family specification gives a static measuring range of ±2.0 mm around the reference position.

6. What is the nominal center air gap?

The nominal center air gap is approximately 2.7 mm. The actual installation setting must be established using the manufacturer’s calibration and installation procedure.

7. Which materials can the sensor measure?

The PR6424 family is designed for use with suitable ferromagnetic targets. The published standard reference material is 42CrMo4 steel.

8. Does the PR6424/102-121 work independently?

No. The sensor requires compatible signal-conditioning electronics to excite the probe and convert its response into a usable measurement signal. A complete monitoring system is needed for alarm, diagnostic, and protection functions.

9. What is the weight of the sensor?

The supplied weight is 0.2 kg. The published PR6424 family specification gives an approximate weight of 200 grams for the sensor with a 1-meter cable and without armor.

10. Can another PR6424 model replace the /102-121?

Not automatically. Although models may share the same family and probe diameter, cable length, connector, mounting arrangement, and other ordering details can differ. Verify the complete model configuration and compatibility with the existing signal converter before replacement.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/102-121, verify the complete model number on the product label. Confirm that the probe, cable, connector, and mounting configuration match the requirements of the existing machinery monitoring system.

For replacement projects, check the matching signal converter and extension cable as well as the sensor itself. A probe with the correct diameter may still be unsuitable if its electrical characteristics or cable configuration differ from the installed unit.

For used or surplus equipment, request clear photographs of the sensor body, cable, connector, and identification label. Inspect the probe tip for visible damage, deformation, contamination, or signs of mechanical impact.

During maintenance, inspect cable routing and mounting stability. Avoid unnecessary movement of the cable and connector, and check for signs of abrasion, heat exposure, or loose mounting hardware.

After replacement, follow the approved calibration procedure. Confirm the installation gap, signal response, and monitoring-system scaling before returning the machine to normal operation.

For critical rotating machinery, sensor replacement and monitoring-system adjustments should be performed by qualified personnel following the plant’s machinery protection and maintenance procedures.

Conclusion

The EPRO PR6424/102-121 16 mm Eddy Current Sensor is designed for non-contact shaft displacement measurement in industrial rotating machinery. Based on the published PR6424 family specifications, it offers 4 V/mm sensitivity, linearity of up to ±1.5%, a static measuring range of ±2.0 mm, and a nominal center air gap of approximately 2.7 mm.

Its applications include turbines, compressors, pumps, fans, and other rotating equipment where shaft movement and vibration measurements are important for condition monitoring.

For maintenance and replacement work, the complete /102-121 ordering configuration must be verified, especially its cable, connector, mounting details, and compatibility with the signal-conditioning electronics. Correct installation and calibration are essential for reliable machinery monitoring.