EPRO PR6423/002-010 CON021 Eddy Current Proximity Sensor – PR6423 Series

EPRO PR6423/002-010 CON021 — Eddy Current Proximity Transducer for Turbomachinery Shaft Monitoring

The EPRO PR6423/002-010 CON021 is a factory-matched eddy current proximity transducer system engineered for continuous, non-contact measurement of radial shaft displacement and vibration in critical rotating machinery. Operating on the principle of electromagnetic induction, the sensor generates a high-frequency oscillating magnetic field at its Ø 8 mm tip; when a conductive target enters this field, eddy currents are induced on the target surface, attenuating the oscillator amplitude in direct proportion to the air gap. The CON021 signal conditioner demodulates this amplitude variation into a calibrated DC voltage output of −24 VDC at full scale, delivering a linear, low-noise analog signal suitable for direct input to machinery protection monitors and DCS/PLC analog input cards.

Designed to API 670 (5th Edition) requirements, the PR6423/002-010 is deployed in steam turbines, gas turbines, centrifugal compressors, and large motor-driven pump trains where shaft displacement excursions beyond alarm and trip thresholds must be detected within milliseconds. The 2 m integral cable minimizes signal path resistance and capacitance mismatch between sensor and conditioner, preserving the calibrated sensitivity of 7.87 V/mm (200 mV/mil) across the full linear measurement range.

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Technical Parameters

Hardware Logical Analysis

Oscillator Circuit and Gap-to-Voltage Conversion: The PR6423 sensor tip houses a precision wound coil embedded in a ferrite core, driven by a Colpitts-type LC oscillator within the CON021 conditioner at a carrier frequency of approximately 1 MHz. As the conductive target approaches the coil, eddy current losses increase, reducing the effective Q-factor of the tank circuit. The CON021 demodulator stage converts this Q-factor depression into a monotonically decreasing DC output voltage. The relationship between gap distance and output voltage is linear within the specified 0–2 mm range, with non-linearity held to ±0.5% of full scale under reference conditions (AISI 4140 steel, 25 °C).

EMC Design and Shielding Architecture: The integral coaxial cable between sensor and conditioner uses a double-braid shield terminated at the conditioner chassis ground, suppressing common-mode interference from variable-frequency drives, high-current bus bars, and RF sources common in turbomachinery enclosures. The CON021 input stage incorporates differential amplification with a common-mode rejection ratio (CMRR) exceeding 80 dB at 50/60 Hz, ensuring that ground potential differences between sensor mounting and control cabinet do not corrupt the displacement signal. The sensor body is constructed from 316L stainless steel, providing both corrosion resistance in oil-mist environments and magnetic neutrality that prevents flux leakage from adjacent ferromagnetic structures from biasing the oscillator.

Thermal Stability and Calibration Traceability: EPRO factory-calibrates each PR6423/CON021 pair as a matched set. The calibration record assigns a unique serial number to both sensor and conditioner, with sensitivity and zero-gap voltage documented at 25 °C. Temperature coefficient of sensitivity is specified at ≤ 0.05%/°C across the operating range, meaning a 60 °C ambient excursion introduces less than 3% sensitivity drift — well within API 670 acceptance criteria. This matched-pair approach eliminates the field calibration uncertainty introduced when mixing sensors and conditioners from different production batches.

Mechanical Mounting and Locknut Torque: The M10 × 1 thread allows precise axial positioning of the sensor tip relative to the shaft surface. The recommended installation gap is 1.0 mm (nominal midpoint of the linear range), set using a DC voltmeter reading −12 VDC at the conditioner output. A stainless steel locknut with a torque specification of 5–7 N·m prevents vibration-induced gap drift during operation. The compact Ø 8 mm tip geometry permits installation in bearing housings with limited radial clearance, a common constraint in retrofitting older turbomachinery frames.

System Integration Benefits

• Direct API 670 compliance: The PR6423/002-010 CON021 meets all transducer performance requirements of API 670 (5th Edition), enabling straightforward acceptance by plant inspection authorities without additional qualification testing.
• Matched-pair calibration eliminates field uncertainty: Factory-paired sensor and conditioner serial numbers ensure the published sensitivity curve is valid without on-site recalibration, reducing commissioning time by eliminating the need for a precision gap-setting fixture and calibrated reference oscilloscope.
• Wide frequency bandwidth supports both static and dynamic measurements: The DC-to-10 kHz flat response captures both slow thermal growth (quasi-static eccentricity) and high-frequency sub-synchronous instabilities such as oil whirl (typically 0.3–0.5× running speed), within a single measurement channel.
• Low output impedance drives long cable runs: The <100 Ω output impedance of the CON021 allows signal transmission over field cables up to 300 m without significant attenuation or susceptibility to capacitive loading, supporting installations where the control room is remote from the machinery train.
• Deterministic analog output for real-time protection: The −24 VDC analog output is processed by the protection monitor without protocol conversion latency, enabling hardware trip response times below 1 ms — a requirement for overspeed and high-vibration trip circuits where digital fieldbus latency is unacceptable.
• Compatibility with major machinery protection platforms: The CON021 output is accepted natively by EPRO MMS 6000/6350, Emerson AMS 6500 ATG, and Bently Nevada 3500 series monitors (with appropriate input card selection), protecting the customer’s investment in existing monitoring infrastructure.
• IP67 sensor body withstands oil-mist and washdown environments: The sealed sensor construction prevents lube oil ingress into the coil assembly, maintaining calibration integrity in bearing pedestals where oil mist concentration can exceed 50 mg/m³.
• Diagnostic transparency through gap voltage monitoring: Because the output voltage is a direct, continuous function of air gap, operators can trend the DC bias voltage over time to detect slow shaft centerline migration caused by bearing wear, thermal bow, or foundation settlement — providing a leading indicator of mechanical degradation before vibration amplitude alarms activate.

Quality Assurance & Global Logistics

Every EPRO PR6423/002-010 CON021 unit supplied by siemensplc.com is sourced through verified channels and subjected to a structured pre-shipment inspection protocol before dispatch from our Xiamen, China facility.

Inspection Protocol: Each unit undergoes visual examination for connector integrity, cable jacket condition, and sensor tip surface finish. Functional verification confirms the conditioner output voltage at a reference gap of 1.0 mm falls within ±2% of the nominal −12 VDC specification. Matched-pair serial number correspondence between sensor and conditioner is confirmed against the factory calibration label. Units are repackaged in anti-static foam-lined cartons with desiccant sachets to prevent moisture ingress during ocean or air freight transit.

Warranty: 12 months from confirmed shipment date. Warranty covers manufacturing defects and calibration non-conformance verified by return inspection. Units damaged by installation error, overvoltage, or mechanical impact are excluded.

Logistics from Xiamen, China: Xiamen Gaoqi International Airport (XMN) and Xiamen Port provide direct access to major air freight and sea freight lanes serving Europe, Southeast Asia, the Middle East, and the Americas. Standard air freight transit times: 3–5 business days to Europe and North America; 2–3 business days to Southeast Asia. Express DHL/FedEx/UPS options available for critical plant shutdown scenarios with next-flight-out booking. All shipments include commercial invoice, packing list, and certificate of origin. Export classification: HS 8543.70 (electronic instruments). No export license required for standard industrial destinations.

Customs Documentation: Full set of shipping documents provided including EPRO original packaging labels, batch traceability records, and pre-shipment inspection report — supporting smooth customs clearance in regulated markets including the EU, UK, and GCC countries.

Contact Information

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