Emerson epro PR6426/000-031 Eddy Current Displacement Sensor

Product Overview

The Emerson epro PR6426/000-031 is an extra-extended range (XER) non-contact displacement sensor. Featuring a large 20mm tip diameter, it is specifically designed to monitor large-scale mechanical shifts that exceed the capabilities of standard sensors. Its primary application is measuring differential expansion—the relative thermal growth between a turbine rotor and its stationary casing—in the world's largest power generation and industrial sets.

Part Number Breakdown

• PR6426: Series for 20mm tip diameter (Extra-Extended Range).
• 000: Indicates a 1.0-meter integrated cable without external stainless steel armoring.
• 031: Specifies the mechanical mounting, typically an M20x1.5 threaded body with a specific stud length optimized for large bearing pedestals.

Technical Specifications

• Sensor Tip Diameter: 20 mm.
• Linear Measuring Range: 8.0 mm (typically from 2.0 mm to 10.0 mm gap).
• Measurement Principle: Non-contact eddy current.
• Frequency Response: 0 Hz (DC) to 10 kHz.
• Target Material: Ferromagnetic steel (Standard: AISI 4140).
• Environmental Rating: IP68; hermetically sealed against oil, steam, and high pressure.
• Operating Temperature: -35°C to +180°C.

Engineering Advantages

The PR6426/000-031 provides an massive 8mm linear window, allowing it to track the significant axial movement of turbine rotors during intense heating and cooling cycles. While smaller 8mm sensors would "bottom out" or go out of range, the 20mm tip maintains high linearity and sub-micron resolution across the entire span. Its non-contact design ensures that even during extreme expansion events, there is no mechanical wear or risk of damage to the rotor surface. The large-format M20 housing provides the mechanical rigidity necessary to prevent sensor vibration in high-flow environments.

FAQs

• What makes the PR6426 different from the PR6424?The PR6426 has a 20mm tip and an 8mm range, whereas the PR6424 has a 12mm tip and a 4mm range. Use the PR6426 for the most extreme axial expansion requirements.
• Can I use this sensor for radial vibration?While technically possible, 20mm sensors are rarely used for radial vibration because the large tip requires a very large target area (shaft diameter). They are almost exclusively used for axial position and expansion.
• Does this sensor require a specific driver?Yes. You must use an epro driver (such as the CON 041) specifically calibrated for 20mm sensors and the total system cable length (e.g., 5m or 10m).
• What is the "side clearance" requirement?Because of the 20mm tip's large electromagnetic field, you must maintain at least 40mm of clear space around the sensor tip (laterally) to prevent interference from surrounding metal, which would distort the reading.