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The Epro PR6424/012-121 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of critical rotating machinery. It belongs to the EPRO PR6424 sensor family, which is used in industrial machinery protection and condition-monitoring applications.
The sensor operates on the eddy current measurement principle. It detects changes in the distance between the probe tip and a conductive metal target without requiring physical contact. This makes it suitable for measuring shaft vibration, radial and axial displacement, shaft position, eccentricity, and rotational speed-related signals in compatible monitoring systems.
The PR6424 series is commonly used in steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These machines contain rotating components whose vibration and displacement characteristics can provide important information about operating conditions. Continuous measurement helps operators and maintenance teams identify abnormal mechanical behavior and assess equipment condition.
The PR6424/012-121 has a specified sensor head diameter of 16 mm and a supplied product weight of approximately 0.2 kg. Its compact probe design allows installation near a rotating shaft, provided that the mounting arrangement, measurement gap, target material, and mechanical clearances meet the applicable requirements.
The sensor is part of a measurement system rather than a standalone general-purpose switch. For a complete installation, it must be matched with compatible extension cable arrangements and signal-conditioning equipment. The precise cable and connector configuration should be verified against the complete model number and the actual product label.
| Parameter | Specification |
|---|---|
| Brand | Epro / EPRO |
| Manufacturer | Emerson |
| Model | PR6424/012-121 |
| Product Series | PR6424 |
| Product Type | Eddy Current Displacement Sensor |
| Sensor Technology | Non-contact eddy current measurement |
| Sensor Head Diameter | 16 mm |
| Sensitivity | 4 V/mm |
| Linearity | ≤ ±1.5% |
| Static Measurement Range | ±2.0 mm |
| Dynamic Measurement Range | 0–1,000 μm |
| Nominal Center Air Gap | Approximately 2.7 mm |
| Long-Term Drift | Less than 0.3% |
| Target Material | Ferromagnetic steel |
| Reference Shaft Diameter | ≥80 mm |
| Sensor Sleeve Material | Stainless steel |
| Cable Material | PTFE |
| Weight Provided | 0.2 kg |
| Typical Series Operating Temperature | Refer to the applicable PR6424 variant datasheet |
| Measurement Application | Shaft vibration, displacement, position, eccentricity, and speed-related monitoring |
| Typical Equipment | Turbines, compressors, pumps, and fans |
Note: The technical performance values above describe the PR6424 16 mm sensor family. Exact temperature limits, cable length, connector type, probe construction, and ordering details should be confirmed for the specific PR6424/012-121 variant. The supplied weight of 0.2 kg is retained as the product listing value.
The PR6424/012-121 uses eddy current technology to measure the distance between the probe tip and a conductive target. Unlike contact-based displacement instruments, it does not need to touch the rotating shaft.
An eddy current sensor contains a coil inside its probe tip. When the compatible signal converter energizes this coil with a high-frequency signal, an electromagnetic field is generated around the sensor tip.
When a conductive metal target approaches the probe, electrical currents known as eddy currents are induced in the target surface. These currents affect the electromagnetic field and change the electrical characteristics of the probe coil.
The associated signal-conditioning equipment detects these changes and converts them into an output related to the distance between the probe and the target.
This allows the system to monitor shaft movement without mechanical contact.
In rotating machinery, a shaft may move relative to its normal operating position because of mechanical loading, bearing conditions, thermal expansion, imbalance, or other operating factors.
The PR6424 sensor can measure changes in the shaft-to-probe distance. Depending on probe placement and system configuration, this information can be used to monitor radial or axial shaft displacement.
Static displacement measurements help establish shaft position, while dynamic measurements provide information about movement during operation.
Shaft vibration is an important condition indicator in turbines, compressors, pumps, and other rotating equipment.
As the shaft moves during rotation, the distance between the shaft surface and the stationary sensor changes. The sensor system converts these variations into an electrical signal that can be processed by a compatible monitoring instrument.
The PR6424 series supports dynamic measurement in the 0–1,000 μm range. Its high-frequency measurement capability makes it suitable for applications requiring detailed shaft-motion monitoring.
The sensor can also be used to monitor shaft position and eccentricity.
Eccentricity refers to the deviation between the shaft’s geometric center and its actual rotational behavior. Excessive eccentricity may indicate mechanical conditions that require further inspection.
By monitoring changes in the sensor gap, maintenance personnel can obtain useful information about shaft position and movement.
When installed in an appropriate arrangement, the PR6424 sensor can detect changes associated with rotating targets and provide signals for speed or key-related monitoring.
The actual measurement function depends on the target geometry, sensor placement, signal converter, and monitoring-system configuration.
The PR6424/012-121 is typically used as a sensing component in a larger machinery monitoring system. Its measurements can help operators evaluate rotating equipment and identify changes that may require maintenance attention.
Steam and gas turbines operate at high rotational speeds and require continuous monitoring of important mechanical parameters.
The sensor can be installed near suitable shaft locations to measure displacement and vibration. When connected to compatible signal-conditioning and monitoring equipment, these measurements can support machinery protection and condition assessment.
Industrial compressors are used in chemical processing, oil and gas production, power generation, and other industrial applications.
Shaft vibration and displacement measurements can help identify changes in rotating behavior. The PR6424 series provides non-contact sensing suitable for appropriately designed compressor monitoring installations.
Large industrial pumps may operate continuously and are often critical to production processes. Monitoring shaft movement can help maintenance teams evaluate mechanical operating conditions.
The sensor can provide measurement signals for use in a compatible monitoring system, helping operators identify abnormal trends that may require inspection.
The PR6424 probe should be connected to compatible signal-conditioning equipment. The converter processes the probe’s measurement signal and provides an output suitable for the monitoring system.
A typical measurement arrangement includes:
| System Component | Function |
|---|---|
| PR6424/012-121 sensor | Detects shaft-to-probe distance changes |
| Extension cable | Connects the sensor to compatible signal-conditioning equipment |
| Signal converter | Conditions the sensor signal and produces a usable output |
| Machinery monitoring unit | Receives and evaluates measurement signals |
| Control or protection system | Uses monitoring information for alarms, protection, or operational decisions |
The exact compatible converter and cable must be confirmed for the probe’s electrical configuration. Components from different sensor variants should not be assumed interchangeable.
Steam turbines are widely used in power generation and industrial energy systems. Their rotating shafts require monitoring to detect vibration and displacement changes.
The PR6424 16 mm sensor family can be used in suitable turbine monitoring installations to measure shaft movement and provide data for machinery condition assessment.
Gas turbines operate under demanding thermal and mechanical conditions. Shaft displacement and vibration monitoring can help identify changes in rotor behavior.
The sensor’s operating limits and installation location must be checked carefully against the actual turbine environment and the specific probe variant.
Hydroelectric generating equipment contains large rotating assemblies that require reliable mechanical monitoring.
Non-contact displacement measurement can support the monitoring of shaft movement and operating stability in suitable hydro turbine applications.
Compressors used in refineries, petrochemical plants, and industrial gas systems may operate continuously under changing process loads.
The PR6424 sensor can provide shaft displacement and vibration measurement signals for compatible compressor monitoring systems.
Large pumps used in water treatment, chemical processing, and energy facilities may require continuous monitoring of rotating components.
The sensor can support measurement of shaft movement when the target material, mounting geometry, and measurement range are suitable.
Large fans used in industrial ventilation and process systems can experience vibration caused by mechanical imbalance, bearing conditions, or changes in operating loads.
A suitable eddy current measurement installation can provide shaft-motion information for machinery monitoring.
Correct installation is essential for reliable measurement. Probe position, target material, mounting rigidity, cable routing, and converter compatibility all influence measurement performance.
The PR6424 series is designed for use with ferromagnetic steel targets. The target material should match the calibration characteristics of the measurement system.
Different materials can produce different measurement responses. If the shaft material differs from the specified reference material, the system’s measurement accuracy may be affected.
The probe should be installed at the measurement location specified by the machinery-monitoring design.
The mounting arrangement must provide sufficient clearance between the sensor and the rotating shaft. The probe should not contact the shaft during normal operation or under expected mechanical movement.
The sensor should be securely fixed to prevent mounting vibration from influencing the measurement.
The PR6424 series has a nominal center air gap of approximately 2.7 mm.
The initial gap must be established according to the applicable sensor and converter instructions. An incorrect gap can reduce the usable measurement range or cause the output to operate outside its intended linear region.
Do not use the nominal air gap as a substitute for the model-specific installation procedure.
The probe must be paired with a compatible signal converter and cable arrangement.
Before installation, verify the exact probe model, cable configuration, connector type, converter model, and required electrical characteristics. Do not assume that every PR6424 probe variant can be connected to every converter.
The sensor cable should be routed away from high-power conductors, strong electromagnetic interference sources, hot surfaces, and moving mechanical components.
Maintain the minimum bending radius specified for the cable. Avoid excessive pulling force, sharp bends, or damage to the cable insulation.
Where the installation requires additional mechanical protection, select suitable accessories that are compatible with the sensor configuration.
After installation, inspect the mounting arrangement and cable connections. Confirm that the converter is configured for the correct sensor type.
Check the initial gap and verify that the output changes appropriately as the distance between the probe and target changes.
The measurement system should be tested under controlled conditions before being used for machinery protection or operational decisions.
The PR6424/012-121 is normally integrated into a complete eddy current measurement arrangement.
| Component | Function | Compatibility Considerations |
|---|---|---|
| PR6424 16 mm sensor | Measures shaft displacement without contact | Match the exact probe variant and calibration |
| Compatible extension cable | Connects the probe to the converter | Verify cable length, connector, and electrical characteristics |
| EPRO signal converter | Converts probe response into a usable measurement signal | Select a converter compatible with the probe configuration |
| Machinery monitoring system | Processes vibration and displacement signals | Confirm input range and signal requirements |
| Protection relay or monitoring unit | Provides alarms and protection functions | Configure according to machinery protection requirements |
| Probe mounting bracket | Holds the sensor in the correct position | Ensure rigidity and suitable adjustment |
| Rotating shaft target | Provides the conductive measurement surface | Confirm ferromagnetic material and suitable surface condition |
The table describes typical system elements. It does not indicate that these components are included with the PR6424/012-121 sensor.
The PR6424 family contains multiple probe configurations. Although they share a 16 mm sensor-head diameter, their cable arrangements, probe lengths, connectors, and other ordering characteristics may differ.
| Alternative Model or Component | Application Consideration |
|---|---|
| EPRO PR6424 series variants | Potential alternatives when measurement range and mechanical configuration match |
| PR6423 series sensors | Smaller sensor-head family for applications designed around an 8 mm probe |
| PR6425 series sensors | Another eddy current sensor family with different application and temperature characteristics |
| Compatible EPRO extension cable | Required when the installation uses a separate cable between probe and converter |
| Compatible EPRO signal converter | Required to condition the sensor signal for the monitoring system |
Before selecting a replacement, compare:
A probe with the same 16 mm diameter is not necessarily a direct replacement. The full ordering code and system compatibility must be checked.
The sensor measures shaft movement without physical contact, avoiding the mechanical wear associated with contact-based measurement methods.
The PR6424 family is designed for applications involving turbines, compressors, pumps, and fans where shaft displacement and vibration monitoring are important.
The series specification of 4 V/mm supports the measurement of small changes in probe-to-target distance when used with the correct converter.
The sensor family supports both static displacement measurement and dynamic shaft-motion measurement, allowing multiple types of mechanical behavior to be monitored.
The 16 mm probe head provides a compact sensing arrangement for suitable installations where the required measurement clearance is available.
The series uses a stainless steel sensor sleeve and PTFE cable construction, supporting use in appropriately specified industrial environments.
When paired with compatible signal-conditioning equipment, the sensor can provide measurement signals for machinery monitoring and protection applications.
The Epro PR6424/012-121 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and vibration in rotating machinery.
The sensor head diameter is 16 mm.
It uses the eddy current principle. An electromagnetic field generated by the probe interacts with a conductive target, and changes in the probe’s electrical characteristics are converted into a distance-related signal.
The published series sensitivity is 4 V/mm, with linearity of up to ±1.5% under the specified measurement conditions.
The PR6424 series has a static measurement range of ±2.0 mm.
The published dynamic measurement range is 0–1,000 μm.
Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans.
A compatible signal-conditioning converter is required for the complete measurement system. The converter processes the probe signal and provides an output for the monitoring equipment.
The PR6424 series is specified for ferromagnetic steel targets, with 42CrMo4 identified as the standard reference material.
The supplied product listing weight is 0.2 kg. PR6424 series documentation also gives approximately 200 grams for the sensor with a 1 m cable and without armor. The actual shipped weight may vary with the cable and packaging configuration.
When purchasing the Epro PR6424/012-121, verify the complete model number printed on the sensor label. This is particularly important because different PR6424 variants may have different probe lengths, cable configurations, connectors, and installation characteristics.
For replacement projects, compare the new sensor with the installed probe and confirm compatibility with the existing signal converter and extension cable. A sensor that shares the same 16 mm head diameter may still have a different electrical or mechanical configuration.
For used or refurbished equipment, inspect the sensor sleeve, probe tip, cable insulation, connector, and mounting thread. Request clear product photographs and any available test information. Confirm whether the quoted weight refers to the sensor alone or includes its cable and packaging.
During maintenance, check that the probe remains securely mounted and that the cable is free from damage. Inspect the sensor-to-shaft clearance and verify that the measurement signal remains stable under the expected operating conditions.
For critical machinery protection systems, sensor replacement and calibration should follow the equipment manufacturer’s procedures and the site’s machinery protection requirements. Do not change probe types or converter settings without verifying the measurement-system compatibility.
The Epro PR6424/012-121 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement and vibration in critical rotating machinery. Its measurement principle allows it to monitor shaft movement without physical contact, making it suitable for properly configured turbine, compressor, pump, and fan monitoring systems.
The PR6424 family provides a sensitivity of 4 V/mm, a static measurement range of ±2.0 mm, and a dynamic measurement range of 0–1,000 μm. With a 16 mm sensor head and a supplied listing weight of 0.2 kg, the PR6424/012-121 can be considered for industrial machinery monitoring and maintenance applications where its exact probe and cable configuration matches the existing system.
Before purchasing or replacing the sensor, verify the complete model number, cable and connector arrangement, converter compatibility, target material, and installation requirements. These checks help ensure reliable measurement and correct integration into the machinery monitoring system.