EPRO PR6426/010-110 + CON021/916-240 Eddy Current Proximity Sensor – PR6426 Series

EPRO PR6426/010-110 + CON021/916-240: Non-Contact Displacement Measurement Chain for API 670 Machinery Protection

The PR6426/010-110 eddy current proximity transducer, paired with the CON021/916-240 signal conditioning converter, constitutes a complete, factory-matched displacement measurement chain designed for continuous operation in critical rotating machinery environments. EPRO — now operating under Emerson Automation Solutions — engineered this series to satisfy the stringent signal integrity, bandwidth, and environmental requirements imposed by API 670 fourth-edition machinery protection standards. The system is deployed globally in steam turbines, gas turbines, centrifugal compressors, expanders, and large motor-driven pump trains where shaft radial displacement, axial position, and differential expansion must be monitored with sub-micron resolution and deterministic response latency.

Unlike general-purpose inductive sensors, the PR6426 series operates on a dedicated high-frequency oscillator circuit embedded within the probe body. The oscillator drives a flat coil wound at the probe tip, generating a focused electromagnetic field that penetrates the conductive target surface. As the air gap between probe face and target changes, eddy currents induced in the target alter the coil impedance. This impedance variation is transmitted via a low-loss coaxial cable to the CON021/916-240 converter, which demodulates the signal and outputs a DC voltage linearly proportional to gap distance. The matched calibration between the PR6426/010-110 probe and the CON021/916-240 converter is performed at the factory against a certified AISI 4140 steel reference target, ensuring the sensitivity coefficient of 8 V/mm is traceable and repeatable across the full linear range of 0.25 mm to 2.25 mm.

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Technical Parameters

Hardware Logical Analysis

The PR6426/010-110 probe integrates a Colpitts-type LC oscillator operating in the 1–2 MHz frequency band. The oscillator coil is wound on a ferrite core and encapsulated in a thermally stable epoxy compound, which maintains dimensional integrity across the full –40 °C to +120 °C operating envelope. This encapsulation also provides the mechanical basis for IP67 sealing without introducing dielectric losses that would degrade oscillator Q-factor.

The coaxial cable connecting the probe to the CON021/916-240 converter is specified with a defined capacitance per meter. EPRO’s matched-pair calibration accounts for the exact cable length (1.0 m for the /010-110 suffix), meaning the oscillator loading is precisely characterized. Substituting a cable of different length or capacitance without recalibration will introduce a systematic offset error — a critical consideration for field replacement procedures.

Within the CON021/916-240 converter, the received RF signal from the probe is processed through a synchronous demodulator stage. The demodulator output passes through a low-pass filter with a –3 dB corner frequency set to 10 kHz, which defines the system’s dynamic bandwidth. This bandwidth is sufficient to capture shaft vibration harmonics up to the 10th order at 60,000 RPM, covering virtually all turbomachinery operating speeds encountered in industrial practice. The DC output stage provides a low-impedance voltage output compatible with the analog input cards of Bently Nevada 3300/3500 series monitors, EPRO MMS6000 modules, and standard DCS/PLC analog input channels (typically 10 kΩ input impedance or higher).

EMC performance is achieved through a combination of coaxial cable shielding (drain wire grounded at the converter end only, per EPRO installation guidelines), the converter’s internal RF filtering on the supply rail, and the inherently differential nature of the gap-proportional output signal. The –24 VDC supply scheme, common across EPRO and Bently Nevada ecosystems, provides a defined common-mode reference that simplifies grounding architecture in multi-channel protection panels.

System Integration Benefits

• Direct API 670 compliance: The PR6426 + CON021 system meets API 670 fourth-edition requirements for proximity transducer systems, enabling direct use in certified machinery protection panels without additional signal conditioning or interface modules.
• Deterministic analog output latency: The DC voltage output from the CON021 has no digital processing delay. Signal propagation from mechanical gap change to converter output is governed only by the 10 kHz low-pass filter group delay (~50 µs), ensuring protection relay trip response times are not degraded by sensor-side latency.
• Matched-pair traceability: Factory calibration of the probe-converter pair against a certified reference target provides a documented sensitivity coefficient. This traceability supports ISO 17025-aligned calibration management programs and simplifies audit compliance for machinery protection systems.
• Wide target material compatibility: While calibrated for AISI 4140, EPRO publishes correction factors for common shaft materials including 17-4PH stainless, Inconel 718, and titanium alloys. This allows the same sensor model to be deployed across mixed-material rotor trains with documented accuracy.
• IP67 probe sealing: The probe assembly withstands continuous immersion in oil mist, coolant, and process condensate environments typical of compressor seal areas and turbine bearing pedestals, eliminating the need for additional protective housings in most installations.
• Broad temperature qualification: The –40 °C to +120 °C probe rating covers both cryogenic service (LNG compressors) and high-temperature applications (steam turbine bearing housings), reducing the need for application-specific sensor variants.
• Low-impedance output drive capability: The CON021 output stage can drive cable runs of up to 300 m to remote monitoring panels without signal degradation, supporting distributed machinery protection architectures in large plant layouts.
• Plug-compatible with existing EPRO/Bently Nevada infrastructure: The –24 VDC supply and voltage output format are electrically identical to Bently Nevada 3300 XL 8 mm proximity transducer systems, allowing the PR6426 + CON021 to serve as a direct replacement in existing panel wiring without rewiring or rescaling.

Quality Assurance & Global Logistics

Every PR6426/010-110 + CON021/916-240 unit dispatched from our Xiamen, China facility is sourced through verified supply channels with full documentation traceability. Pre-shipment inspection covers visual examination of probe tip geometry, connector integrity, cable armor continuity, and functional verification of the converter output against a calibrated gap standard. Serial numbers are cross-referenced against EPRO/Emerson production records where available, and a Certificate of Conformance is issued with each shipment.

Export documentation — commercial invoice, packing list, and certificate of origin — is prepared in compliance with Chinese customs regulations and the import requirements of the destination country. Shipment is via DHL Express, FedEx International Priority, or UPS Worldwide Expedited as standard, with sea freight consolidation available for multi-unit orders. Transit times to major industrial hubs: Europe 3–5 business days, North America 4–6 business days, Southeast Asia 2–3 business days. All shipments are fully insured and tracked from dispatch to delivery confirmation.

The 12-month warranty covers manufacturing defects and functional failure under normal operating conditions as defined in the EPRO installation manual. Warranty claims are processed with a replacement-first policy to minimize plant downtime.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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