Bently Nevada 330703-000-100-50-12-00 Proximity Probe – 3300 XL Series

Bently Nevada 330703-000-100-50-12-00: 3300 XL 11mm Eddy-Current Proximity Probe for Critical Rotating Machinery

The Bently Nevada 330703-000-100-50-12-00 is a factory-calibrated, 11 mm eddy-current proximity probe belonging to the 3300 XL Series — Bently Nevada’s precision non-contact measurement platform for continuous shaft vibration and axial position monitoring. This specific configuration encodes a 100-inch (2,540 mm) probe cable, a 50-inch (1,270 mm) extension cable, and a 12-pin connector termination, making it a defined, non-interchangeable assembly within the three-component probe system architecture (probe body + extension cable + driver/oscillator).

The probe operates on the eddy-current induction principle: a high-frequency oscillator in the paired driver (e.g., Bently Nevada 330180-X1-05) drives an LC tank circuit through the probe tip coil. As a conductive target — typically AISI 4140 steel shaft — enters the electromagnetic field, induced eddy currents load the tank circuit, reducing oscillation amplitude. This amplitude modulation is demodulated into a DC voltage output with a nominal sensitivity of 7.87 V/mm (200 mV/mil), providing a linear, low-noise analog signal proportional to gap distance across a measurement range of 0.25 mm to 2.54 mm (10 to 100 mil).

Deployed in steam turbines, centrifugal compressors, boiler feed pumps, and gearboxes, the 330703-000-100-50-12-00 is a primary sensing element in API 670-compliant machinery protection systems. Its stainless steel housing, rated to −35 °C to +177 °C at the probe tip, sustains measurement integrity in high-temperature bearing housings and process-adjacent installations without signal drift attributable to thermal expansion of the probe body.

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Technical Parameters

Hardware Logical Analysis

The 3300 XL probe system is architecturally distinct from single-component eddy-current sensors. The three-component matched-set design — probe body, extension cable, and driver/oscillator — distributes the LC resonance circuit across physically separated elements. The probe tip coil forms the inductive element; the extension cable contributes a defined capacitive and resistive load; the driver houses the oscillator and demodulator. This distributed architecture means the system is calibrated as an assembly: substituting any single component without recalibration introduces gain error proportional to the impedance mismatch.

EMC Design: The probe cable is a coaxial assembly with a continuous shield bonded at the driver end only (single-point grounding), preventing ground-loop currents that would appear as low-frequency noise on the output signal. The shield termination at the 12-pin connector is specified to maintain shield continuity through the extension cable junction, sustaining common-mode rejection across the full cable run. In environments with high-frequency switching noise (VFD-driven auxiliaries, arc furnaces), the coaxial geometry provides >40 dB attenuation of radiated interference at frequencies above 1 MHz.

Thermal Stability: The probe tip coil is wound on a ceramic bobbin with a low coefficient of thermal expansion (CTE ≈ 5 ppm/°C), matched to the stainless steel housing. This minimizes thermally induced inductance shift across the −35 °C to +177 °C operating range, keeping sensitivity drift below ±0.5% over the full thermal envelope — a critical requirement in steam turbine bearing housings where ambient temperatures can cycle 80–120 °C during startup and shutdown sequences.

Gap Voltage Linearity: The eddy-current field penetration depth is a function of target conductivity and permeability. For AISI 4140 steel at 1 MHz excitation, skin depth is approximately 0.08 mm, ensuring the field interacts only with the shaft surface layer. This confines the measurement to surface geometry rather than bulk material properties, providing repeatable linearity even in shafts with internal bore variations. For non-ferrous targets (aluminum, titanium), the reduced permeability shifts the linear range and sensitivity — field recalibration with the actual target material is mandatory.

System Integration Benefits

• Deterministic analog output: The DC voltage output (−18 VDC nominal) is directly compatible with Bently Nevada 3300 series monitor input cards without signal conditioning, eliminating A/D conversion latency in the field wiring segment.
• API 670 compliance out of the box: The probe assembly meets API 670 5th Edition requirements for radial vibration and axial position measurement without additional field certification, reducing commissioning documentation burden.
• Matched-set traceability: Each probe, extension cable, and driver is serialized and calibration-matched at the factory. The calibration certificate references all three serial numbers, providing a single traceable document for the complete measurement chain — a requirement in ISO 55001 asset management frameworks.
• Broad monitor compatibility: The 330703-000-100-50-12-00 interfaces directly with 3300/16 Dual Voting, 3300/20 Radial Vibration, 3300/25 Thrust Position, and 3500 series monitor cards, supporting both legacy and current-generation Bently Nevada rack architectures.
• Diagnostic transparency: The −18 VDC bias voltage at nominal gap is continuously readable by the monitor as a gap OK / gap fault indicator. A bias voltage outside the −10 to −22 VDC window triggers a Not OK (NOK) relay output, providing automatic probe-health diagnostics without additional instrumentation.
• Non-contact measurement eliminates wear: Unlike contact-type displacement transducers, the eddy-current probe has no mechanical interface with the rotating shaft. MTBF data from field installations in gas turbine applications exceeds 10 years continuous operation, with probe replacement driven by cable degradation rather than sensing element wear.
• High-frequency bandwidth for transient capture: The DC-to-10,000 Hz frequency response captures sub-synchronous instabilities (oil whirl at 0.43–0.48× running speed), synchronous 1× imbalance, and super-synchronous blade-pass frequencies in a single measurement channel, eliminating the need for parallel high-frequency accelerometers in many applications.
• Hazardous area deployment: ATEX certification permits installation in Zone 1 and Zone 2 classified areas (gas group IIC, temperature class T4) when paired with the appropriate certified driver, supporting refinery and offshore platform installations without additional intrinsic safety barriers in the probe circuit.

Quality Assurance & Global Logistics

Every 330703-000-100-50-12-00 unit supplied through siemensplc.com is sourced from verified industrial distribution channels with full chain-of-custody documentation. Pre-shipment inspection covers visual and dimensional verification against OEM drawings, electrical continuity and insulation resistance testing (≥100 MΩ at 500 VDC), coaxial cable shield integrity check, and packaging seal verification. A Certificate of Conformance (CoC) is available for each unit; calibration documentation referencing the matched driver serial number is available on request for critical applications.

Shipments originate from our warehouse in Xiamen, China. Standard export packaging uses anti-static foam inserts within double-wall corrugated cartons, with desiccant packs for humidity-sensitive cable assemblies. Typical dispatch lead time is 1–3 business days for in-stock units. International freight options include DHL Express (3–5 days to most destinations), FedEx International Priority, and sea freight consolidation for bulk orders. All shipments include tracking numbers and commercial invoices with HS code 9031.80 for customs clearance. Export compliance documentation (EAR99 classification) is provided for US-destination shipments.

Contact Information

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