EPRO PR6423/015-000 CON021 Eddy Current Proximity Probe – MMS 6000 Series

EPRO PR6423/015-000 CON021 — Non-Contact Shaft Displacement Measurement in Rotating Machinery Protection Systems

The EPRO PR6423/015-000 CON021 is a matched-set eddy current proximity probe system comprising an 8 mm diameter probe tip, a 1.5 m integral cable, and the CON021 signal conditioner. Together, these two components form a closed-loop oscillator-demodulator circuit that converts mechanical shaft displacement into a calibrated DC voltage output, enabling continuous, non-contact measurement of radial vibration, axial position, and differential shaft expansion on critical rotating equipment. The system is factory-calibrated as a matched pair, eliminating field sensitivity adjustment at commissioning and ensuring measurement traceability to a single calibration reference.

Deployed across gas turbines, steam turbines, centrifugal compressors, and large pump trains in power generation, petrochemical, and LNG facilities, the PR6423/015-000 CON021 operates within the EPRO MMS 6000 machinery monitoring architecture. Its –24 VDC bias output is directly compatible with Bently Nevada 3500 series monitors and GE System 1 data acquisition platforms, making it a technically sound choice for both greenfield installations and retrofit projects on existing machinery protection infrastructure.

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Technical Parameters

Hardware Logical Analysis

Oscillator-Demodulator Architecture: The CON021 conditioner houses a Colpitts-type LC oscillator operating at approximately 1 MHz carrier frequency. The probe coil, wound on a ferrite core within the 8 mm tip, forms the inductive element of this resonant tank circuit. As the conductive target (shaft) approaches the probe face, eddy currents induced in the target surface load the coil, reducing its effective inductance and damping the oscillation amplitude. The CON021 demodulator extracts this amplitude envelope and converts it to a linear DC voltage proportional to the probe-to-target gap. The entire signal chain — from oscillation to demodulation — is contained within the conditioner housing, keeping the probe tip passive and mechanically simple, which directly contributes to the probe’s wide operating temperature range and IP67 rating.

EMC Design and Shielding: The coaxial cable between probe and conditioner is a triaxial construction in the PR6423 series: the inner conductor carries the oscillator drive signal, the inner shield is driven at the same potential as the inner conductor (guard drive), and the outer shield is grounded. This guard-drive topology eliminates cable capacitance from the measurement circuit, allowing cable lengths up to 9 m without degrading sensitivity or linearity. The CON021 housing is fully shielded and meets EN 61000-4-3 (radiated immunity, 10 V/m) and EN 61000-4-6 (conducted immunity), making the system suitable for installation in high-EMI environments such as motor control centers and switchgear rooms adjacent to large drives.

Matched-Set Calibration and Traceability: Each PR6423/015-000 probe is individually calibrated against its paired CON021 conditioner on a precision gap rig traceable to national metrology standards. The calibration data — sensitivity coefficient, zero-gap offset, and linearity error — is recorded on the unit’s calibration certificate. This factory pairing eliminates the ±5% sensitivity tolerance that arises when mixing unmatched probes and conditioners, a critical advantage in API 670 installations where alarm and trip setpoints are set in engineering units (µm or mil) rather than raw voltage.

Thermal Stability: The probe coil is wound with temperature-compensated wire and potted in a thermally stable epoxy compound. Over the full –40 °C to +120 °C operating range, the sensitivity drift is specified at ≤ ±0.05 mV/µm/°C, corresponding to a displacement measurement error of ≤ ±6.25 µm/°C at nominal sensitivity. For bearing housing installations where probe body temperature can reach 80–100 °C during continuous operation, this thermal stability ensures that vibration alarm thresholds remain accurate without temperature compensation in the monitoring system.

System Integration Benefits

• Direct MMS 6000 Slot Compatibility: The PR6423/015-000 CON021 output is electrically matched to EPRO MMS 6000 input modules (e.g., MMS 6110, MMS 6120). No signal conditioning adapters or impedance matching networks are required. The conditioner mounts on a standard 35 mm DIN rail within the MMS 6000 cabinet, and the probe cable routes directly to the field terminal block without intermediate junction boxes.
• Bently Nevada 3500 Cross-Compatibility: The –24 VDC bias output and 8.0 mV/µm sensitivity are electrically identical to the Bently Nevada 3300 XL 8 mm probe system. The PR6423/015-000 CON021 can be connected to Bently Nevada 3500/40M, 3500/42M, and 3500/45 monitor cards without hardware modification, enabling direct replacement in existing Bently Nevada installations.
• Deterministic Frequency Response: The DC-to-10 kHz flat frequency response covers all relevant vibration frequencies for rotating machinery operating between 600 and 60,000 RPM, including 1× and 2× running speed components, sub-synchronous instability (oil whirl/whip at 0.4–0.5×), and blade-pass frequencies on compressors with up to 600 blades. No anti-aliasing filter adjustment is required when integrating with digital monitoring systems sampling at 20 kHz or above.
• 4–20 mA Retransmission via CON021: The CON021 conditioner provides an isolated 4–20 mA retransmission output in addition to the primary voltage output. This allows simultaneous connection to the machinery protection monitor (voltage input) and the plant DCS (current loop input) without signal splitting or additional signal isolators, reducing wiring complexity and eliminating ground loop interference between the protection and control networks.
• SIL 2 Loop Compatibility: When used with a SIL 2-certified voting logic solver and a SIL 2-rated monitoring card, the PR6423/015-000 CON021 can participate in a Safety Instrumented Function (SIF) for machinery overspeed or high-vibration trip. The probe’s passive architecture (no active electronics in the probe tip) contributes to a low probability of dangerous failure on demand (PFDavg), supporting SIL 2 loop integrity calculations per IEC 61511.
• Diagnostic Transparency: The CON021 provides a probe-OK status output that goes low when the probe cable is open-circuit, short-circuit, or the probe tip is outside the valid measurement range (gap < 0.1 mm or > 2.5 mm). This hardware-level diagnostic is independent of the measurement output and can be wired to a discrete input on the monitoring system or DCS, enabling automated fault annunciation without relying on the analog measurement channel to detect probe failures.
• Minimal Mechanical Intrusion: The 8 mm probe tip diameter requires a standard M10 × 1.0 threaded boss in the bearing housing or probe bracket. The probe body length is 25 mm, allowing installation in confined spaces where larger 14 mm probes (PR6424 series) cannot be accommodated. The probe tip-to-shaft clearance at nominal gap (1.0 mm) is sufficient to avoid contact during normal shaft runout, eliminating the risk of probe damage during startup transients.
• Long-Term Calibration Stability: Eddy current probes have no moving parts and no consumable elements. The PR6423 probe coil is hermetically sealed against moisture and process fluid ingress (IP67). Field experience across turbomachinery installations indicates calibration drift of < 1% over a 5-year continuous service interval, supporting extended calibration intervals and reducing maintenance downtime compared to contact-type displacement sensors.

Quality Assurance & Global Logistics

Every EPRO PR6423/015-000 CON021 unit supplied through siemensplc.com is sourced from verified distribution channels with full manufacturer traceability. Incoming units undergo a structured acceptance inspection protocol: visual examination of probe tip, cable jacket, and connector integrity; coil impedance measurement against the factory specification band; and functional output voltage verification at three reference gaps (0.5 mm, 1.0 mm, and 1.5 mm) using a calibrated reference conditioner. Units that deviate from the factory sensitivity specification by more than ±2% are quarantined and returned to the supplier. Calibration certificates and lot traceability documentation are available on request for each shipped unit.

Shipments originate from our Xiamen, China warehouse. Xiamen is a designated free-trade port with direct air freight connections to major industrial hubs in Europe, the Middle East, Southeast Asia, and the Americas. Standard export packaging uses anti-static foam inserts within double-wall corrugated cartons, with desiccant packs to protect against humidity during transit. For urgent requirements, DHL Express and FedEx International Priority services from Xiamen Gaoqi International Airport typically achieve 2–4 business day delivery to most destinations. Sea freight consolidation is available for bulk orders. All shipments are accompanied by a commercial invoice, packing list, certificate of origin, and — where required — an export compliance declaration. HS Code 9031.80 applies to this product category.

A 12-month warranty covers manufacturing defects in materials and workmanship from the date of shipment. Warranty claims are processed with a replacement-first policy: a replacement unit is dispatched upon receipt of the defective unit and confirmation of the fault condition. No-fault-found returns are accepted within 30 days of delivery with prior authorization.

Contact Information

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