Product Overview

The Epro PR6426/010-100 is a 32 mm eddy current sensor used for non-contact measurement of shaft displacement, position, eccentricity, and movement in large rotating machinery. It belongs to the PR6426 sensor family and is commonly applied in turbine, compressor, pump, and other critical machinery monitoring installations.

Unlike contact-based displacement measurement devices, the PR6426 detects changes in the distance between the probe and a conductive metallic target without physically touching the rotating surface. This makes it suitable for continuous monitoring of shafts operating inside journal bearings, where the rotor moves relative to the bearing housing and conventional vibration sensors mounted on the casing may not capture the actual shaft movement.

The PR6426/010-100 has a 32 mm sensing head and a mounting plate measuring 80 × 40 mm. Its mounting arrangement is intended for installations where the probe is positioned close to a large shaft or dedicated measuring collar. The sensor requires sufficient clearance around the sensing head to avoid interference from nearby ferrous structures.

The PR6426/010-100 is particularly relevant to large rotating equipment in which shaft displacement needs to be measured directly. On a steam turbine, for example, probes can be positioned near the rotor to monitor axial movement and radial shaft vibration. In a centrifugal compressor, the same measurement principle can be used to detect changes in shaft position during startup, normal operation, and load transitions.

The sensor operates with compatible signal converters such as the CON011 and CON021, as well as suitable transmitter systems with integrated conversion electronics. The converter excites the sensing coil and processes the resulting signal, allowing the measurement to be transmitted to a machinery monitoring system.

For the standard PR6426 measuring configuration, the sensor has a static range of ±4.0 mm and a nominal sensitivity of 2 V/mm. Its nominal center measuring gap is approximately 5.5 mm when used with the standard measuring range. These characteristics make it suitable for monitoring relatively large shaft movements while retaining a defined linear measurement region.

The /010-100 designation identifies a particular mechanical and cable configuration within the PR6426 family. It should not be treated as interchangeable with other PR6426 variants solely because they share the same 32 mm sensing head. Cable protection, connection arrangement, and mounting details should be checked when selecting a replacement.

Technical Specifications

Product Features

• 32 mm Sensing Head: Suitable for large-shaft displacement measurement in turbines, compressors, and other heavy rotating equipment.
• Non-Contact Measurement: Detects shaft movement through electromagnetic interaction without mechanical contact with the target.
• Defined Linear Measuring Range: Supports a standard static measurement range of ±4.0 mm.
• Nominal Sensitivity of 2 V/mm: Converts small changes in probe-to-target distance into measurable electrical variations.
• Armored Cable Configuration: Provides additional mechanical protection for cable installations exposed to potential physical damage.
• Mounting Plate Construction: Uses an 80 × 40 mm mounting arrangement rather than a conventional threaded sensor sleeve.
• High-Temperature Capability: The sensor supports demanding machinery environments, with a specified short-term temperature excursion of up to 200°C.
• Converter Compatibility: Works with compatible CON011 and CON021 signal conversion equipment.
• Machinery Monitoring Applications: Supports shaft displacement, eccentricity, and movement measurement in rotating equipment.

Working Principle

The PR6426/010-100 operates through the eddy current principle. Its sensing coil generates an alternating electromagnetic field near the probe face. When the sensor is positioned close to a conductive metallic shaft, the field induces eddy currents in the target material.

These currents produce an opposing electromagnetic field that changes the electrical characteristics of the sensor circuit. The magnitude of this interaction depends on the distance between the probe and the shaft.

As the rotor moves, the air gap changes. The resulting variation in the sensor signal is processed by a compatible converter, which produces an electrical output corresponding to the measured displacement.

The measurement sequence is:

Rotating Shaft → PR6426/010-100 → Signal Cable → CON011 / CON021 → Monitoring Input → Machinery Protection System

For a standard PR6426 measuring chain, the nominal sensitivity is 2 V/mm, with a static measuring range of ±4.0 mm. The nominal center air gap is approximately 5.5 mm.

Consider a steam turbine operating under changing thermal and mechanical loads. As the rotor moves axially or radially, the distance between the probe and the measuring surface changes. The PR6426 detects this movement and sends the corresponding signal to the converter.

The converter processes the signal into a voltage output that can be evaluated by the connected monitoring equipment. This allows operators to observe shaft position changes and distinguish normal operating movement from displacement conditions that may require investigation.

The measuring response depends on the target material. The standard calibration reference is 42CrMo4 steel, also known as SAE 4140. If the actual shaft material differs, the measurement chain may require material-specific adjustment.

The sensor and converter should therefore be considered as one measurement system rather than two independently selected components.

Role in a Machinery Protection and Condition Monitoring Architecture

The PR6426/010-100 serves as the sensing element in a rotating machinery displacement monitoring channel. It measures the physical movement of the shaft and supplies the corresponding signal to compatible conversion and monitoring equipment.

A typical measurement arrangement follows this sequence:

Machine Shaft → PR6426/010-100 → Signal Converter → Monitoring Transmitter → Machinery Protection System

In a turbine protection installation, multiple PR6426 sensors can be positioned around the shaft to monitor different measurement points. Radial probes detect shaft movement relative to the bearing housing, while appropriately positioned axial probes measure rotor displacement along the shaft axis.

The converted signals are transmitted to the monitoring system, where displacement trends can be evaluated against configured alarm and trip thresholds.

The PR6426 itself is a measurement transducer, not a standalone protection relay. Alarm processing, shutdown logic, and machinery interlocks are handled by the connected monitoring and protection equipment.

Industrial Applications

Installation and Maintenance

1. Verify the Sensor Configuration: Check the complete PR6426/010-100 model designation, sensor identification, cable protection, and connection arrangement before installation.
2. Inspect the Sensing Head: Examine the 32 mm sensor head and stainless-steel sleeve for impact damage, contamination, or deformation.
3. Check the Mounting Structure: Ensure that the 80 × 40 mm mounting plate can be secured to a rigid, vibration-free support.
4. Select the Measuring Position: Determine whether the sensor will monitor radial shaft movement or axial displacement. Position the probe toward the appropriate measuring surface.
5. Confirm the Target Material: Verify that the shaft material matches the standard 42CrMo4 reference material or that the measuring chain has been adjusted for the actual material.
6. Inspect the Shaft Surface: Check the measuring track for corrosion, scratches, deposits, and surface irregularities that could introduce measurement errors.
7. Maintain Sufficient Clearance: For the PR6426, provide at least 80 mm of free space around the sensing head as required by the specified installation arrangement.
8. Adjust the Measuring Gap: Set the probe position using the complete sensor and converter measuring chain. For the standard ±4.0 mm configuration, the nominal center air gap is approximately 5.5 mm.
9. Secure the Mounting Plate: Tighten the mounting hardware and use the specified anti-rotation provisions to prevent the assembly from shifting during machine operation.
10. Route the Armored Cable: Protect the cable from rotating parts, excessive bending, mechanical tension, and unsuitable temperature conditions. Keep the cable and connector clear of moving machine components.
11. Connect the Signal Converter: Connect the sensor to a compatible CON011 or CON021 arrangement. Check the connector condition and verify the converter configuration before energizing the measuring chain.
12. Perform Measurement Verification: Check the converter output across the intended measuring range. Confirm the initial gap, signal direction, sensitivity, and monitoring-system indication before placing the measurement channel into service.

Compatible System Components

Recommended Related Models

Key Advantages

• 32 mm sensing head for large-shaft measurement.
• Non-contact detection of radial and axial displacement.
• Standard static measuring range of ±4.0 mm.
• Nominal sensitivity of 2 V/mm.
• Linearity error of ≤ ±1.5%.
• Armored cable configuration for additional mechanical protection.
• Stainless-steel sensor construction.
• Compatible with CON011 and CON021 conversion equipment.
• Suitable for turbine, compressor, pump, and fan monitoring installations.

Technical FAQs

What is the difference between PR6426/010-100 and PR6426/000-100?

Both belong to the PR6426 32 mm sensor family, but their ordering configurations differ. The /010-100 version specifies an armored cable configuration, whereas the /000-100 version uses a non-armored cable configuration. The selection depends on the mechanical protection required along the cable route.

Can the PR6426/010-100 operate without a CON011 or CON021 converter?

The sensor requires compatible excitation and signal-processing electronics to form a complete measurement chain. CON011 and CON021 are suitable converter families for compatible PR6426 configurations. The sensor should not be treated as a standalone voltage-output transmitter.

What measuring range should be used when configuring the PR6426/010-100?

For the standard PR6426 configuration, the static measuring range is ±4.0 mm, with a nominal sensitivity of 2 V/mm. Extended measuring ranges require the corresponding converter configuration and calibration. The sensor’s measuring range should therefore be selected according to the actual converter and monitoring application.

Why is sufficient clearance around the 32 mm sensor head necessary?

The PR6426 uses an electromagnetic sensing field, so nearby ferrous structures can influence its measurement characteristics. The installation arrangement requires at least 80 mm of free space around the sensor head. Insufficient clearance can reduce the usable measuring range and increase linearity error.