Product Overview

The Epro PR6426/010-040 is a 32 mm eddy current sensor used for non-contact measurement of shaft displacement in rotating machinery. It belongs to the PR6426 family of sensors used in machinery monitoring applications where engineers need to observe shaft position, eccentricity, and movement without placing a mechanical measuring element in contact with the rotating surface.

In a steam turbine, the sensor can be installed near a bearing to measure the shaft’s position relative to the stationary machine structure. In an industrial compressor, displacement measurements help maintenance engineers examine rotor behavior during startup, changes in operating load, and investigations into unexpected vibration. Similar arrangements are used in pumps, gas turbines, and industrial fans when continuous shaft-position monitoring is required.

The PR6426/010-040 functions as the sensing element in a complete measurement channel. Its electromagnetic field interacts with the conductive shaft surface, and changes in the sensor-to-target gap alter the electrical response. Compatible signal-conditioning equipment processes this response into a signal that can be interpreted by the machinery monitoring system.

The complete model number is important when identifying a replacement. Although several PR6426 variants share the same nominal sensor-head diameter, their connection arrangements and other configuration details may differ. The /010-040 designation should therefore be matched against the installed probe and its associated measuring equipment rather than selected by diameter alone.

During installation, particular attention should be paid to the mounting position, initial air gap, target material, cable condition, and signal-converter compatibility. These factors influence the measurement response and help determine whether the sensor can be integrated correctly into an existing machinery monitoring channel.

Technical Specifications

The performance values above describe the standard PR6426 sensor specification. The actual measuring characteristics depend on the applicable sensor configuration, compatible converter, target material, and calibration.

Product Features

• Non-contact displacement measurement: Detects relative movement between the sensing head and a conductive target without mechanical contact with the rotating shaft.
• 32 mm sensor-head configuration: Supports installations built around the PR6426 mounting arrangement, subject to the required clearance and target geometry.
• Static and dynamic measurement capability: The PR6426 family supports measurements of shaft position and movement, including applications involving eccentricity and shaft vibration.
• Defined measuring characteristics: The standard PR6426 configuration specifies a nominal sensitivity of 2 V/mm and a static measuring range of ±4.0 mm.
• Electromagnetic sensing: Changes in the distance between the sensor and target produce corresponding changes in the sensor’s electrical response.
• Industrial sensor construction: A stainless-steel sleeve and PTFE cable form part of the sensor construction, with operating limits determined by the applicable configuration.
• Converter-based integration: Compatible signal-conditioning equipment processes the sensor response for use by machinery monitoring electronics.
• Model-specific identification: The complete /010-040 designation helps distinguish this probe from other PR6426 configurations during maintenance and spare-parts selection.

Working Principle

The PR6426/010-040 operates through electromagnetic coupling between its internal sensing coil and a conductive target. When compatible electronics excite the coil, an alternating electromagnetic field forms around the sensing head. This field induces eddy currents in the target, affecting the electrical characteristics of the coil.

As the shaft moves relative to the stationary sensor, the gap between the sensing head and the target changes. The corresponding change in electromagnetic coupling alters the sensor response. A compatible signal converter processes that response and produces an electrical output associated with the target’s position.

The measurement path is:

Conductive Shaft Target → PR6426/010-040 Sensor → Compatible Signal Converter → Machinery Monitoring System

For the standard PR6426 measuring configuration, the nominal sensitivity is 2 V/mm, with a static measuring range of ±4.0 mm. These values apply to the specified measuring arrangement and should not be assumed to establish every configuration-specific characteristic of the /010-040 variant.

The initial air gap establishes the sensor’s operating point. If the probe is positioned too close to the target, available measurement travel may be restricted in one direction. If the gap is too large, the sensor may operate outside the intended linear region. Correct positioning is therefore necessary before the channel is commissioned.

Target material also affects the measurement response. Ferromagnetic steel, specifically 42CrMo4, is the standard reference material for the PR6426 family. When the actual shaft material differs, its effect on the calibrated measuring chain should be evaluated.

The monitoring system interprets the conditioned signal according to its configured scale and operating limits. Engineers can compare displacement readings with shaft speed, vibration, temperature, and process conditions to investigate changes in machine behavior. The sensor supplies measurement data; determining the cause of an abnormal reading requires assessment of the complete machine and measurement channel.

Role in the Machinery Monitoring Architecture

The PR6426/010-040 occupies the sensing stage of a shaft-displacement measurement channel. It detects movement between the rotating target and the stationary sensor mounting point. Compatible electronics then process the sensor response for display, recording, and evaluation by the monitoring system.

In a turbine installation, the measurement channel can be used to observe shaft-position changes near a bearing. In a compressor, the resulting readings can be assessed alongside vibration and operating data to investigate rotor movement under different loads.

The sensor, converter, and receiving input must be treated as a coordinated measuring chain. A replacement probe that fits the mounting arrangement may still require verification of the connection, calibration, and monitoring-channel scaling before it can be placed into service.

Industrial Applications

Installation and Maintenance

1. Verify the complete model designation: Confirm PR6426/010-040 against the installed probe and maintenance records. Do not select a replacement solely because it belongs to the PR6426 family.
2. Check converter compatibility: Verify that the installed signal converter supports the specific sensor configuration. Confirm the connection arrangement, measuring range, and calibration requirements before installation.
3. Inspect the target surface: Examine the shaft measurement area for damage, deposits, or surface conditions that could affect the sensing response. Confirm that the target material is appropriate for the calibrated measuring chain.
4. Prepare the mounting arrangement: Inspect the mounting bracket, fixing points, and supporting surface. The probe must remain stationary relative to the machine structure during operation.
5. Set the initial air gap: Adjust the distance between the sensing head and target according to the applicable installation procedure. Do not estimate the gap from the sensor-head diameter or copy a setting from an unverified variant.
6. Check surrounding metal clearance: Inspect nearby ferrous components that could influence the electromagnetic field. Ensure that the probe’s installation meets the clearance requirements for the actual sensor arrangement.
7. Inspect the sensing head: Check the sleeve and sensing area for impact damage, deformation, or contamination. Ensure that the probe can be secured without applying unnecessary mechanical stress.
8. Examine the cable route: Look for cuts, crushing, abrasion, and excessive bending. Keep the cable away from moving parts and heat sources beyond the applicable operating limits.
9. Verify the electrical connection: Confirm that the cable termination and connector match the receiving electronics. Check connection security before energizing the measuring channel.
10. Test the sensor response: Follow the approved commissioning procedure to verify that changes in target position produce the expected electrical response. Investigate abnormal readings before returning the channel to service.
11. Validate monitoring-channel settings: Check the configured measurement range, engineering units, signal polarity, and alarm limits. Ensure that the settings correspond to the installed sensor and converter combination.
12. Document the final configuration: Record the complete sensor designation, converter identification, initial gap, cable arrangement, and commissioning results. These details help maintenance personnel reproduce the intended setup during future replacement work.

Compatible System Components

The exact converter and connection arrangement must be checked against the installed measuring chain. The shared PR6426 family designation alone does not confirm that all converters, cables, or mounting accessories are directly interchangeable.

Recommended Related Models

Key Advantages

• Non-contact measurement of relative shaft displacement.
• 32 mm sensor-head configuration for compatible PR6426 installations.
• Defined measuring characteristics for the standard PR6426 configuration.
• Stainless-steel sleeve and PTFE cable construction.
• Integration with compatible signal converters and machinery monitoring systems.

Technical FAQs

What should be verified before replacing a PR6426/010-040 with another sensor in the same series?

Check the complete ordering code, cable termination, connector arrangement, mounting requirements, target material, and converter compatibility. A matching head diameter does not establish direct interchangeability.

Can the PR6426/010-040 measure both static shaft position and dynamic movement?

The PR6426 family supports static shaft-displacement measurements as well as dynamic measurements associated with shaft movement. The usable measurement depends on the sensor-converter combination, monitoring input, calibration, and configured signal-processing range.

What can cause an incorrect displacement reading even when the sensor is electrically connected?

An incorrect initial gap, loose mounting, unsuitable target material, cable damage, converter mismatch, or incorrect monitoring-channel scaling can all affect the reading. Confirm the entire measurement chain before concluding that the sensor itself has failed.

Why should the converter configuration be recorded when replacing the sensor?

The converter determines how the sensor response is conditioned for the monitoring system. Recording its model and output configuration helps preserve the intended scaling and makes it easier to verify readings after maintenance.