Product Overview

The Epro PR6424/106-021 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of industrial rotating machinery. It belongs to the PR6424 sensor family developed for applications where accurate measurement of shaft movement, vibration, and position is important for equipment reliability and machinery protection.

Manufactured under the EPRO product range associated with Emerson, the PR6424 series is commonly used in critical rotating equipment such as steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. Instead of making physical contact with the rotating shaft, the sensor uses eddy current technology to measure the distance between its sensing tip and a conductive target.

The PR6424/106-021 is identified as a 16 mm eddy current sensor. Its supplied sensor head diameter is 16 mm, and its listed weight is approximately 0.2 kg. The probe is intended to work as part of a compatible measurement system, which normally includes signal-conditioning electronics and a monitoring or protection device.

Eddy current sensors are particularly useful in machinery monitoring because they can continuously measure shaft movement without mechanical contact at the sensing point. The resulting measurement information can help operators and maintenance engineers identify changes in vibration, shaft position, eccentricity, and other operating conditions.

The PR6424 family offers a nominal sensitivity of 4 V/mm, a static measurement range of ±2.0 mm, and a dynamic measurement range of 0 to 1,000 μm under the published family specifications. Exact cable length, connector arrangement, temperature limits, and other ordering details should be checked against the complete PR6424/106-021 configuration before installation or replacement.

Technical Specifications

Note: The performance figures above are published PR6424 family specifications, not a separately verified complete configuration sheet for the /106-021 suffix. Confirm exact cable, connector, temperature, and installation details before use.

Function and Working Principle

The PR6424/106-021 uses the eddy current principle to measure the distance between the probe tip and a conductive target. This measurement method allows the sensor to monitor rotating shafts without direct mechanical contact.

1. Eddy Current Measurement

An eddy current probe contains a coil inside its sensing head. When the compatible measurement electronics energize the coil, an electromagnetic field forms around the probe tip.

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

The associated signal-conditioning electronics detect this change and convert it into a measurement signal corresponding to the distance between the probe and the target.

2. Shaft Displacement Measurement

The sensor can measure changes in the position of a rotating shaft relative to the probe mounting point.

This information is useful for monitoring shaft movement caused by bearing clearance, thermal expansion, mechanical loading, or other operating conditions. Engineers can use the measurements to assess machine behavior and identify changes that may require inspection.

3. Vibration Monitoring

When a shaft rotates, it may move slightly around its normal operating position. The sensor continuously detects changes in the probe-to-shaft gap.

The resulting dynamic measurement can be used to evaluate shaft vibration. When installed as part of a suitable monitoring system, the sensor provides information that helps identify abnormal vibration patterns and changes in rotating equipment condition.

4. Position and Eccentricity Monitoring

The PR6424 family can also support static position and eccentricity measurements.

Shaft eccentricity refers to the variation in the distance between the shaft surface and a fixed measurement reference as the shaft rotates. Monitoring this behavior can help engineers evaluate alignment, shaft condition, and mechanical stability.

5. Signal Conversion and Monitoring

The sensor probe is normally connected to a compatible EPRO signal converter or measurement channel. The converter processes the probe response and produces an output suitable for monitoring equipment.

The probe itself is not a standalone display or protection device. Correct pairing with the associated electronics is necessary for meaningful measurements.

Role in Industrial Machinery Protection Systems

The PR6424/106-021 can serve as a sensing element within a broader machinery condition monitoring and protection arrangement.

Turbine Shaft Monitoring

Steam, gas, and hydro turbines operate under demanding mechanical and thermal conditions. Shaft displacement and vibration measurements provide important information about the behavior of rotating components.

A correctly installed eddy current sensor can supply measurement data for evaluating shaft movement and identifying abnormal operating trends.

Compressor Condition Monitoring

Industrial compressors often operate continuously in production and process facilities. Changes in shaft vibration or position may indicate developing mechanical problems.

The PR6424 sensor family is designed for applications involving critical rotating machinery, including compressors. Its measurement output can be incorporated into a compatible machinery monitoring system.

Pump Monitoring

Large industrial pumps may experience vibration changes caused by hydraulic conditions, bearing wear, alignment problems, or mechanical imbalance.

Non-contact shaft measurement provides useful information for condition monitoring and maintenance planning.

Integration with Monitoring Equipment

A complete measurement arrangement may include:

• PR6424 eddy current sensor.
• Compatible signal converter.
• Extension cable or approved connection accessories, where required.
• Machinery monitoring channel.
• Alarm and protection system.
• Plant control or supervisory monitoring equipment.

The exact arrangement depends on the monitoring platform and the installation requirements. Compatibility should be confirmed before replacing a probe or modifying an existing measurement channel.

Industrial Applications

1. Steam Turbines

Steam turbines require continuous monitoring of shaft behavior to support reliable operation. Eddy current sensors can measure radial shaft displacement and dynamic movement, providing information for machinery condition monitoring.

The PR6424 family is designed for critical turbomachinery applications and can be used where the required measurement range and installation conditions are suitable.

2. Gas Turbines

Gas turbines operate at high rotational speeds and elevated temperatures. Monitoring shaft displacement and vibration helps maintenance teams assess mechanical performance and identify unusual operating trends.

The sensor’s temperature limits and mounting arrangement must be checked against the actual turbine installation.

3. Hydro Turbines

Hydro turbine systems contain large rotating assemblies that require monitoring during continuous operation. Shaft position and vibration measurements can help evaluate rotor movement and mechanical stability.

The PR6424 series can be considered for suitable hydro turbine monitoring arrangements.

4. Industrial Compressors

Compressors are widely used in chemical processing, oil and gas facilities, power generation, and manufacturing plants.

Shaft vibration and displacement measurements can provide useful information about the condition of bearings, rotating assemblies, and other mechanical components.

5. Industrial Pumps

Pumps in process plants often operate for extended periods. Monitoring shaft movement can help maintenance personnel identify changes associated with mechanical wear, misalignment, or unstable operation.

6. Industrial Fans

Large industrial fans and ventilation systems may experience vibration caused by imbalance, bearing deterioration, or mechanical changes.

When installed with compatible electronics, the sensor can contribute to a machinery monitoring arrangement that tracks shaft movement over time.

Installation and System Integration

Correct sensor installation is essential for obtaining stable and reliable measurements. The probe, target surface, mounting arrangement, cable, and signal converter must be treated as one measurement system.

1. Verify the Sensor Configuration

Before installation, confirm the complete model number PR6424/106-021 and compare it with the existing sensor or equipment documentation.

Check the probe’s connector, cable length, mounting thread, mechanical dimensions, and compatible converter. Do not assume that every PR6424 probe variant has identical connection details.

2. Check the Target Surface

The PR6424 family is specified for measurement against a suitable ferromagnetic steel target, with 42CrMo4 steel used as the standard reference material in published specifications.

Target material and surface condition can influence measurement performance. Confirm that the actual shaft material and measurement surface are suitable for the selected probe system.

3. Maintain the Correct Probe Gap

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

The actual installation gap should be set according to the relevant sensor and converter instructions. Incorrect probe positioning may reduce measurement accuracy or cause the signal to operate outside its intended linear range.

4. Observe Mounting Requirements

Install the sensor using the mounting arrangement specified for the exact probe variant. Ensure that the probe is securely fixed and correctly aligned with the measurement target.

Avoid excessive mechanical force during tightening. The sensing tip and cable connection should be protected from accidental damage.

5. Route and Protect the Cable

Cable routing is important in rotating machinery installations. Keep sensor cables away from high-current power conductors and sources of electromagnetic interference where required.

Avoid sharp bends, excessive tension, and contact with hot or moving components. Follow the specified minimum bending radius and temperature limitations for the actual cable assembly.

6. Connect Compatible Signal Electronics

The PR6424 sensor must be paired with suitable EPRO signal-conditioning electronics. Verify the probe and converter compatibility, cable arrangement, and connector configuration before energizing the measurement channel.

Incorrect combinations may produce unreliable readings or prevent the system from operating correctly.

7. Verify Measurement Performance

After installation, check the sensor gap, signal stability, measurement output, and channel configuration. Compare the readings with expected operating conditions and the machine’s commissioning records.

Document the installation details and baseline measurements to support future condition monitoring.

Compatible System Components

The PR6424/106-021 is normally used as part of a complete eddy current measurement system. The following components describe typical system roles rather than confirming that every listed component is supplied with this sensor.

Alternative Models and Replacement Considerations

The PR6424 family contains different ordering variants. Although they share the same general 16 mm eddy current measurement principle, individual models may differ in cable length, connector arrangement, mechanical configuration, and other ordering details.

Before selecting an alternative, compare the following:

• Sensor head diameter.
• Complete probe ordering number.
• Measurement range and sensitivity.
• Probe mounting thread and mechanical dimensions.
• Cable length and cable construction.
• Connector and extension cable arrangement.
• Compatible signal converter.
• Target material and shaft diameter.
• Operating temperature and environmental limits.
• Monitoring channel requirements.

A sensor with the same 16 mm head diameter may still be unsuitable if its electrical or mechanical configuration differs from the original unit.

Key Advantages

Non-Contact Measurement

The sensor measures shaft movement without physical contact at the sensing point. This makes it suitable for continuous monitoring of rotating machinery.

Suitable for Critical Machinery

The PR6424 family is designed for applications involving turbines, compressors, pumps, and fans, where reliable shaft measurement is important.

Static and Dynamic Measurement

The sensor family supports both static displacement and dynamic vibration measurement within its specified operating range.

Compact 16 mm Sensing Head

The 16 mm sensor head supports installation in suitable machinery measurement locations where a larger probe may not be appropriate.

High Measurement Sensitivity

The published family sensitivity of 4 V/mm supports the conversion of small changes in probe-to-target distance into a measurable electrical response.

Industrial Construction

The stainless-steel sleeve and PTFE cable materials specified for the PR6424 family support use in demanding industrial measurement environments, subject to the exact model’s operating limits.

Integration with Machinery Monitoring Systems

When paired with compatible signal-conditioning and monitoring equipment, the sensor can provide data for machinery condition assessment and protection.

Technical FAQs

1. What is the Epro PR6424/106-021?

The PR6424/106-021 is identified as an EPRO PR6424-series 16 mm eddy current sensor. It is designed for non-contact measurement applications involving shaft displacement, vibration, and position.

2. What is the sensor head diameter?

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

3. How does the PR6424/106-021 measure shaft displacement?

It uses eddy current technology. An electromagnetic field is generated at the probe tip, and changes in the conductive target’s distance affect the probe’s electrical response. Compatible electronics convert this response into a measurement signal.

4. What is the typical sensitivity of the PR6424 family?

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

5. What is its measurement range?

The published family specification gives a static measurement range of ±2.0 mm and a dynamic measurement range of 0 to 1,000 μm. Confirm the applicable specification for the exact probe and converter combination.

6. Does this sensor require a signal converter?

Yes. The probe normally operates with compatible EPRO signal-conditioning electronics. The converter processes the probe response and supplies a measurement signal to the monitoring system.

7. Where is the PR6424 series commonly used?

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

8. What target material is recommended?

The published PR6424 family specification identifies ferromagnetic steel as the target material, with 42CrMo4 used as the standard reference material. Actual target compatibility should be checked during system design.

9. What is the weight of the PR6424/106-021?

The supplied product listing weight is approximately 0.2 kg. The published PR6424 family specification also gives a reference weight of approximately 200 grams for the sensor with a 1-meter cable and without armor. Actual weight may vary with cable and accessory configuration.

10. Can the PR6424/106-021 replace another PR6424 sensor?

Not automatically. The complete ordering number should be compared, including cable length, connector, mounting details, and converter compatibility. Matching the 16 mm sensor head diameter alone is insufficient to confirm replacement suitability.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/106-021, verify the complete model number and inspect the physical configuration carefully. Confirm the sensor head diameter, cable length, connector arrangement, mounting details, and any included accessories.

For replacement projects, compare the existing probe with the proposed unit and check compatibility with the installed signal converter and machinery monitoring channel. A probe with similar dimensions may still have a different electrical or mechanical configuration.

For critical rotating machinery, installation and maintenance should follow the equipment manufacturer’s procedures. Inspect the sensing tip, cable insulation, connector, and mounting hardware for damage. Check cable routing and make sure the probe remains securely positioned.

After installation, record the measurement gap and baseline readings. Monitoring changes over time can help maintenance teams identify unusual shaft movement and investigate potential mechanical issues before they develop into more serious equipment problems.

For long-term reliability, maintain accurate records of sensor model numbers, cable configurations, converter settings, and replacement dates. This information can simplify future maintenance and reduce the risk of installing an incompatible sensor.

Conclusion

The Epro PR6424/106-021 16 mm Eddy Current Sensor is a non-contact measurement probe intended for monitoring shaft displacement, vibration, and position in industrial rotating machinery. Its 16 mm sensing head and approximately 0.2 kg supplied weight make it a compact component for suitable machinery monitoring installations.

The PR6424 family offers a published 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 capabilities support condition monitoring applications involving turbines, compressors, pumps, and fans.

For successful installation or replacement, engineers should verify the complete probe configuration, compatible signal converter, cable arrangement, target material, and installation gap. Correct system matching is essential for reliable measurement and effective machinery monitoring.