EPRO PR6424/010-010 CON021 Eddy Current Sensor – PR6424 Series

EPRO PR6424/010-010 CON021 — Non-Contact Displacement Sensor for Turbomachinery Protection

The EPRO PR6424/010-010 CON021 is an 8 mm eddy current proximity sensor assembly comprising a threaded sensor probe, a 1.0 m integral extension cable, and the CON021 signal conditioner. The three-component set operates as a factory-calibrated system, delivering a DC voltage output linearly proportional to the air gap between the probe tip and a conductive target surface. Within turbomachinery protection architectures governed by API 670, this assembly is the primary transducer for radial shaft vibration, axial position (thrust), differential expansion, and phase-reference (Keyphasor) measurements. Its non-contact operating principle eliminates mechanical wear, making it suitable for continuous, unattended monitoring in gas turbines, steam turbines, centrifugal compressors, and high-speed pumps operating at shaft speeds from a few hundred to tens of thousands of RPM.

The PR6424 probe body is machined from stainless steel with an M10×1 threaded shank, allowing direct installation into standard API 670 proximity probe brackets without adapter hardware. The integral cable terminates in a MIL-C-5015-style connector that mates directly with the CON021 driver, preserving the factory calibration curve. The CON021 conditioner accepts a −24 VDC bias supply and outputs a voltage in the range of approximately −2 VDC to −18 VDC across the linear measurement span, with a nominal sensitivity of 8 mV/µm when measured against AISI 4140 steel targets. This output is directly compatible with EPRO MMS 6000 and MMS 6350 monitoring rack input cards, as well as with third-party 4–20 mA converters for integration into DCS or safety instrumented systems.

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Technical Parameters

Hardware Logical Analysis

The PR6424 probe operates on the Lenz’s law induction principle. An oscillator within the CON021 driver energizes a coil embedded in the probe tip at a fixed carrier frequency, generating a high-frequency electromagnetic field that penetrates the target surface. When a conductive target enters this field, eddy currents are induced, loading the coil and reducing its effective impedance. The CON021 demodulates this impedance change into a DC voltage with a transfer function that is linear across the specified gap range for the calibrated target material.

EMC Design: The coaxial cable between probe and CON021 is impedance-matched and shielded with a braided outer conductor referenced to the driver chassis ground. This construction attenuates common-mode noise from adjacent high-voltage switchgear and variable-frequency drives, which are prevalent in turbomachinery installations. The CON021 enclosure is designed to meet IEC 61000-4 immunity levels for conducted and radiated disturbances, ensuring measurement integrity in environments with significant electromagnetic interference from motor drives and power cables.

Thermal Stability: The probe coil former uses a low-thermal-expansion ceramic composite, limiting sensitivity drift to less than ±0.05% per °C across the operating range. This is critical in steam turbine casings where ambient temperatures can vary by 60–80 °C between cold startup and full-load steady state.

Matched-System Calibration: The PR6424/010-010 and CON021 are serialized and calibrated as a matched pair at the factory. The calibration data is encoded in the CON021 driver, meaning the sensitivity and linearity specifications are only guaranteed when the original matched pair is used together. Substituting a different cable length or a different conditioner variant (CON011, CON031) will shift the transfer function and require field recalibration against a reference gap standard.

Redundancy Architecture: In API 670-compliant installations, two or three PR6424 probes are typically mounted 90° apart (X–Y configuration) on the same bearing journal. The MMS 6000 rack performs vector summation of the two orthogonal displacement signals to compute orbit plots and overall vibration amplitude, providing redundant measurement paths. If one probe fails open-circuit or short-circuit, the CON021 driver output saturates to a defined fault voltage (typically below −20 VDC or above −1 VDC), which the monitoring rack interprets as a transducer fault without triggering a false machinery trip.

System Integration Benefits

• Direct API 670 compliance: The PR6424/010-010 CON021 assembly meets all transducer performance requirements of API 670 (5th Edition) without supplementary hardware, simplifying FAT and SAT documentation for new installations and replacement projects.
• Zero mechanical wear: Non-contact measurement eliminates probe-to-shaft contact, removing the primary failure mode of contact-type displacement sensors and extending mean time between maintenance (MTBM) to the life of the installation.
• Deterministic frequency response: The flat frequency response from DC to 10 kHz covers all relevant vibration harmonics for machinery operating up to 600,000 CPM (10,000 Hz), including sub-synchronous instability, synchronous unbalance, and high-order blade-pass frequencies.
• Plug-compatible with EPRO MMS 6000/6350 racks: The CON021 output voltage range and connector pinout are natively accepted by EPRO monitoring rack input cards, eliminating signal conditioning adapters and reducing wiring complexity.
• Fault-state output discrimination: The CON021 driver produces defined out-of-range voltages for open-circuit and short-circuit probe faults, enabling the monitoring system to distinguish a genuine machinery alarm from a transducer wiring fault — a critical diagnostic transparency feature in unmanned or remote installations.
• Target material flexibility: While factory-calibrated for AISI 4140 steel, the PR6424 can be field-calibrated for stainless steel (AISI 316), titanium, and other conductive alloys, broadening its applicability to compressor impellers and non-ferrous shaft materials.
• Compact probe geometry: The 8 mm tip diameter and M10×1 thread fit standard API 670 proximity probe holders without machining modifications, reducing installation time and enabling like-for-like replacement of legacy EPRO and compatible third-party probes.
• Integrated cable strain relief: The MIL-C-5015 connector at the cable-to-driver junction incorporates a backshell strain relief, preventing cable fatigue failures at the termination point in high-vibration environments such as compressor skids and turbine pedestals.

Quality Assurance & Global Logistics

Every PR6424/010-010 CON021 unit supplied by siemensplc.com is sourced through verified distribution channels with full part traceability back to the EPRO manufacturing facility. Incoming units undergo a structured inspection protocol: visual examination of probe tip, cable jacket, and connector contacts; continuity and insulation resistance verification of the coaxial cable; and documentation review confirming the matched serial numbers of probe and CON021 driver. Units are stored in a temperature- and humidity-controlled warehouse to prevent connector oxidation and cable insulation degradation prior to shipment.

Shipments originate from our logistics hub in Xiamen, China. Standard export packaging uses anti-static foam inserts within double-wall corrugated cartons, with silica gel desiccant packs to protect connector contacts during ocean or air transit. DHL Express and FedEx International Priority services are available for time-critical orders, with typical transit times of 3–5 business days to Europe, North America, and Southeast Asia. For bulk orders, sea freight consolidation via Xiamen Port is available with full export documentation including commercial invoice, packing list, and certificate of origin. A 12-month warranty covers manufacturing defects; units exhibiting electrical failure under normal operating conditions within the warranty period are replaced or credited without charge.

Contact Information

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