Product Overview

The Epro PR6426/000-030+CON021/916-160 is an extended-range eddy current measurement assembly consisting of a PR6426 32 mm sensor and a CON021/916-160 signal converter. It is used for non-contact displacement measurement in large rotating machinery, particularly where shaft movement requires a wider measuring interval than standard proximity measurement configurations can accommodate.

The assembly combines the sensing capability of the PR6426 with the extended-range signal processing of the CON021/916-160. The probe detects changes in the distance between its sensing face and a metallic target, while the converter processes the sensor response and generates a voltage output proportional to the measured displacement.

The /916-160 converter designation identifies a 16.0 mm extended measuring range for the PR6426 sensor family. Its nominal measuring-chain sensitivity is -1.0 V/mm, with a specified linearity error of ≤ ±2.0%. This differs from the /916-120 version, which has a 12.0 mm measuring range and approximately -1.33 V/mm sensitivity.

The sensor component, PR6426/000-030, uses a 32 mm sensing head, a non-threaded sleeve, and an 80 × 40 mm mounting plate. Its mechanical arrangement is suitable for large turbine and compressor installations where the probe must be secured to a fixed structure and positioned toward a shaft or measuring collar.

This particular sensor version comes with an 8 m non-armored PTFE cable, an adapter plug, and a LEMO connector. The cable length is useful when the measuring point is located inside a machine housing while the converter is installed in a separate instrumentation panel.

The 16 mm measuring range is relevant to applications involving comparatively large shaft position changes. For example, in a large steam turbine, the assembly can monitor axial rotor displacement over a wider interval. In compressor installations, it can be applied to suitable shaft position measurement points where the expected displacement exceeds the range of a standard measuring chain.

The CON021/916-160 is a panel-mounted converter. Its front-mounted LEMO socket accepts the sensor connection, while screw terminals provide the DC supply and measurement output. The extended-range version has a fixed output voltage range of -4 to -20 V rather than the selectable output arrangement available on standard CON021 converters.

The sensor and converter must be treated as one calibrated measuring chain. The sensor identification, converter version, target material, and installation gap all affect the resulting measurement. When replacing an existing assembly, matching only the sensor diameter or converter family is insufficient; the actual extended measuring range must also correspond to the original application.

Technical Specifications

PR6426/000-030 Eddy Current Sensor

CON021/916-160 Eddy Current Signal Converter

Complete Assembly

Product Features

• Complete eddy current measurement assembly combining PR6426 and CON021.
• 32 mm sensing head for large rotating machinery.
• 16.0 mm extended measuring range.
• -1.0 V/mm nominal measuring-chain sensitivity.
• Linearity error of ≤ ±2.0%.
• Fixed -4 to -20 V converter output range.
• Non-threaded sensor sleeve with 80 × 40 mm mounting plate.
• 8 m non-armored PTFE sensor cable.
• LEMO connector and adapter plug.
• Panel-mounted CON021 signal converter.
• Self-locking sensor input connection.
• Screw-terminal DC supply and signal output.
• Frequency response up to 20 kHz (-3 dB).
• Rise time below 15 μs.
• Suitable for extended-range static and dynamic shaft displacement measurement.

Working Principle

The PR6426/000-030 and CON021/916-160 operate together through an electromagnetic eddy current measuring principle. The sensor detects the changing distance between its sensing head and a conductive metallic target, while the converter processes the resulting electrical response into a displacement-related voltage signal.

The sensor contains a measuring coil connected to an oscillator circuit inside the CON021. The oscillator generates a high-frequency signal, producing an alternating magnetic field around the probe tip. When this field reaches a metallic shaft surface, it induces eddy currents in the target.

These currents generate an opposing magnetic field that changes the oscillator amplitude. The amount of damping depends on the distance between the sensing head and the target. A smaller gap produces greater damping, while a larger gap produces less damping.

The converter then demodulates, linearizes, and amplifies the response. Its output terminals provide a voltage signal proportional to the actual distance between the sensor and the measuring target.

The complete measurement path is:

Rotating Shaft → PR6426/000-030 → 8 m Sensor Cable → CON021/916-160 → -4 to -20 V Output → Machinery Monitoring System

The /916-160 configuration extends the measuring interval to 16.0 mm. Its nominal sensitivity is -1.0 V/mm, meaning that a change of 1 mm in the measured distance corresponds to approximately 1 V of output change within the calibrated linear range.

For example, on a large turbine, the probe can be installed at an axial displacement measurement point. As the rotor moves, the distance between the shaft target and sensor changes. The converter processes this movement over the extended measuring interval, allowing the monitoring equipment to track a wider range of shaft position changes.

The fixed -4 to -20 V output arrangement is another characteristic of the extended-range converter. Unlike standard CON021 versions with selectable output ranges, the /916-160 uses a fixed output configuration. The receiving monitoring input must therefore be configured for the correct negative voltage signal.

The sensor and converter are calibrated together. During installation, the physical distance between the sensing head and target is adjusted while monitoring the converter output. This ensures that the actual measurement point falls within the intended 16 mm characteristic curve.

Role in a Machinery Protection and Condition Monitoring Architecture

The PR6426/000-030+CON021/916-160 serves as a complete displacement measurement channel in a rotating machinery protection architecture. The sensor performs the physical measurement, and the converter generates the processed signal required by the monitoring equipment.

A typical arrangement follows this sequence:

Rotating Shaft → PR6426/000-030 → 8 m LEMO Cable → CON021/916-160 → Monitoring Input → Machinery Protection System

The extended measurement range is useful when the monitoring point must accommodate a wider displacement interval. In large steam turbines, for instance, axial rotor movement can vary during startup, loading, and shutdown. A suitably selected extended-range measuring chain allows these changes to be monitored without exceeding the configured measurement interval.

The converter output is transmitted to a compatible monitoring input, where the measured voltage is interpreted as shaft displacement. The monitoring system can then evaluate trends and compare the measurement against configured alarm and trip limits.

The -4 to -20 V output must be considered during system integration. The receiving protection card or measuring amplifier must support the converter’s negative voltage signal and the required scaling. Incorrect input scaling can result in misleading displacement readings even when the sensor and converter are functioning correctly.

The sensor and converter identification should also be retained as a matched pair. Their calibration relationship is essential to maintaining the specified sensitivity and linearity.

Industrial Applications

Installation and Maintenance

1. Verify the Complete Model: Confirm that the assembly consists of PR6426/000-030 and CON021/916-160. Check the 8 m cable, LEMO termination, adapter plug, and converter type plate.
2. Inspect the Sensor Head: Examine the 32 mm sensing head, stainless-steel sleeve, cable, and mounting plate for mechanical damage before installation.
3. Select the Measuring Position: Determine whether the probe is being used for radial or axial displacement measurement. Position the sensing face toward the appropriate shaft measuring surface.
4. Check the Mounting Environment: Ensure that nearby ferrous structures do not interfere with the electromagnetic field or restrict the intended measuring arrangement.
5. Inspect the Target Material: Confirm that the measuring surface is compatible with the standard 42CrMo4 reference material or that the measuring chain has been calibrated for the actual shaft material.
6. Prepare the Mounting Support: Use a rigid, vibration-free mounting structure. The mounting plate must remain fixed during machine operation to prevent changes in the measurement reference position.
7. Adjust the Measuring Gap: Move the sensor mounting flange or bracket until the CON021 output reaches the required point on the 16 mm characteristic curve. Do not use the standard-range probe adjustment value without checking the extended-range configuration.
8. Secure the Sensor: Fix the mounting plate and secure all screws and nuts against loosening. Ensure that the sensor is mounted vertically relative to the measuring target.
9. Route the 8 m Cable: Keep the non-armored PTFE cable away from rotating components, sharp edges, and excessive tension. Maintain the minimum 25 mm bending radius.
10. Connect the LEMO Interface: Insert the sensor connector into the converter’s self-locking LEMO socket. Check the connector engagement and inspect the contacts for contamination.
11. Verify Power and Output Wiring: Supply the converter with the specified -24 V DC nominal supply. Connect the -4 to -20 V output to a compatible monitoring input and verify the input scaling before commissioning.
12. Test the Complete Measuring Chain: Check the output across the intended displacement interval, verify the measurement direction and sensitivity, and record the final mounting position, sensor identification, converter model, and output settings.

Compatible System Components

Recommended Related Models

Key Advantages

• Complete sensor and converter measurement assembly.
• 32 mm sensing head for large rotating machinery.
• 16.0 mm extended measuring range.
• -1.0 V/mm nominal measuring-chain sensitivity.
• Linearity error of ≤ ±2.0%.
• Fixed -4 to -20 V output configuration.
• 8 m cable for installations requiring additional distance between the probe and converter.
• LEMO sensor connection with adapter plug.
• Panel-mounted converter with screw-terminal power and output connections.
• Suitable for extended-range static and dynamic shaft displacement measurement.
• Integration with compatible machinery monitoring and protection systems.

Technical FAQs

What is the difference between CON021/916-160 and CON021/916-120?

Both converters are intended for extended-range measurement with the PR6426 sensor family, but they support different measuring intervals. The /916-120 provides a 12.0 mm range with a linearity error of ≤ ±1.5%, while the /916-160 provides a 16.0 mm range with a linearity error of ≤ ±2.0%. Their nominal sensitivities are approximately -1.33 V/mm and -1.0 V/mm, respectively.

Why does the CON021/916-160 have a lower sensitivity than the standard CON021?

The /916-160 distributes the converter’s fixed -4 to -20 V output across a wider 16 mm measuring interval. As a result, its nominal sensitivity is -1.0 V/mm. A standard PR6426 configuration has a narrower measuring range and a higher nominal sensitivity. The appropriate version should be selected according to the expected shaft displacement and required measurement resolution.

Can the CON021/916-160 use the same output settings as a standard CON021?

No. The extended-range /916-160 converter has a fixed -4 to -20 V output configuration. Standard CON021 converters can have selectable output ranges, depending on their configuration. The monitoring input must be set to accept the extended-range converter’s fixed negative voltage output.

Why must the PR6426 sensor and CON021 converter remain a matched pair?

The converter is calibrated for a specific sensor and measuring range. Their combined characteristics determine the output sensitivity, linearity, and displacement measurement response. Using an incorrectly matched converter can produce inaccurate shaft position readings, even if the physical sensor connection is compatible. The sensor identification and serial number should therefore be checked against the converter type plate during replacement.