Bently Nevada 330850-90-05 Proximitor Sensor – 3500 Series

Bently Nevada 330850-90-05 Proximitor Sensor — Eddy-Current Signal Conditioner for Rotating Machinery Protection

The Bently Nevada 330850-90-05 is a field-proven eddy-current Proximitor® signal conditioner engineered for continuous, non-contact measurement of shaft radial vibration, axial position, and eccentricity in critical rotating machinery. Deployed across gas turbines, steam turbines, centrifugal compressors, and large pump trains, this unit forms the signal-conditioning backbone of the Bently Nevada 3500 Series Machinery Protection System. Its architecture converts the raw inductance variation from a paired 3300 XL 8 mm probe into a calibrated DC voltage output, delivering a linear scale factor of 200 mV/mil (7.87 V/mm) across a 0–90 mil (0–2.29 mm) measurement range — parameters that are directly consumed by 3500 monitor cards without any intermediate signal processing or recalibration.

Unlike generic eddy-current conditioners, the 330850-90-05 is factory-matched to the 3300 XL probe system. The internal oscillator frequency, demodulation circuit, and temperature-compensation network are co-optimized with the probe’s coil geometry, ensuring that the combined system error remains within ±1% of full-scale across the full operating temperature band of −35 °C to +85 °C. This level of factory integration eliminates the field-calibration burden that accompanies third-party substitutions and preserves the measurement chain integrity required by API 670 Fourth Edition for machinery protection in oil and gas installations.

The unit operates from a single −24 VDC supply rail (−18 to −26 VDC tolerance), drawing less than 25 mA under normal operating conditions. The output is a low-impedance DC voltage referenced to the supply common, making it directly compatible with the differential input stages of all 3500 series monitor cards. The 5-pin MIL-C-5015 style connector provides robust field termination with positive locking, rated for repeated mating cycles in maintenance-intensive environments.

In turbomachinery protection architectures, the 330850-90-05 is typically installed in a probe-extension cable-Proximitor chain, where the Proximitor is mounted outside the bearing housing at a distance determined by the extension cable length. The standard 5 m extension cable configuration (suffix -05) accommodates the majority of industrial installations where the Proximitor must be located away from high-temperature bearing zones. The unit’s sealed housing provides IP67-equivalent ingress protection, allowing installation in areas subject to wash-down, condensation, or hydrocarbon mist.

From a control-loop perspective, the 330850-90-05 occupies the sensor-conditioning layer between the physical measurement point and the protection logic. Its output feeds directly into the 3500/40M or 3500/42M Proximitor monitor cards, which perform alert and danger setpoint comparison, gap voltage monitoring, and OK relay logic. The deterministic response time of the Proximitor output — with a signal bandwidth of DC to 10 kHz — ensures that subsynchronous instabilities, oil whirl, and rub events are captured with sufficient temporal resolution for the monitor’s digital signal processor to execute trip decisions within the 20 ms response window mandated by API 670.

All units supplied by siemensplc.com are sourced through verified distribution channels with full part traceability. Each unit undergoes pre-shipment inspection covering connector integrity, housing condition, and label verification. Certificates of conformance are available upon request. Stock is held in Xiamen, China, enabling rapid dispatch to global destinations via DHL Express, FedEx International Priority, and UPS Worldwide Expedited, with typical transit times of 3–7 business days to major industrial hubs in Europe, the Middle East, Southeast Asia, and the Americas.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The 330850-90-05 implements a three-stage signal chain: oscillator generation, eddy-current demodulation, and output buffering. The internal LC oscillator drives the probe coil at a fixed frequency (nominally 1 MHz for the 3300 XL 8 mm system), establishing a stable electromagnetic field at the probe tip. As the conductive target shaft moves within this field, eddy currents induced in the shaft surface load the oscillator circuit, causing a proportional change in oscillator amplitude. The demodulation stage rectifies and filters this amplitude-modulated carrier, producing a DC voltage linearly proportional to the probe-to-target gap.

The temperature-compensation network — implemented as a passive resistor-capacitor ladder tuned to the probe coil’s thermal coefficient — corrects for the inductance drift of the probe across the −35 °C to +85 °C operating band. This compensation is factory-trimmed per probe-Proximitor pair, which is why mixing probe and Proximitor from different matched sets degrades system accuracy. The output buffer stage presents a low source impedance (<100 Ω), enabling cable runs of up to 300 m to the monitor rack without significant signal attenuation or susceptibility to capacitive loading.

EMC performance is achieved through a combination of internal shielding of the oscillator circuit, a ferrite bead filter on the supply input, and the coaxial construction of the extension cable. The result is a unit that maintains measurement integrity in environments with variable-frequency drive (VFD) switching noise, high-voltage bus bars, and RF transmitters — conditions common in petrochemical and power generation control rooms.

System Integration Benefits

• Direct 3500 Monitor Compatibility: The 200 mV/mil scale factor and −24 VDC bias are natively recognized by all 3500 series Proximitor monitor cards, eliminating any input scaling configuration and reducing commissioning time.
• Deterministic Signal Latency: The analog output path introduces no digital processing delay. The DC-to-10 kHz bandwidth ensures that the monitor’s DSP receives vibration data with sub-millisecond latency, supporting the 20 ms trip response requirement of API 670.
• Gap Voltage Diagnostics: The 3500 monitor continuously evaluates the Proximitor output voltage at rest to confirm the probe is within its linear range. An out-of-range gap voltage triggers an OK relay state change, providing automatic fault detection without additional instrumentation.
• Non-Contact Measurement Architecture: Eliminates mechanical wear at the measurement point. The probe tip maintains a fixed air gap to the rotating shaft, producing zero friction and zero influence on shaft dynamics — critical for high-speed machinery above 10,000 RPM.
• Multi-Parameter Measurement from a Single Channel: A single 330850-90-05 channel can simultaneously provide radial vibration (AC component), average shaft position (DC component), and slow-roll runout data to the monitor, reducing channel count and wiring complexity.
• API 670 Compliance for Regulatory Acceptance: Installations using original Bently Nevada components with factory calibration documentation satisfy the instrumentation traceability requirements of API 670, simplifying insurance, audit, and regulatory approval processes.
• Broad Monitor Platform Compatibility: While optimized for the 3500 series, the −24 VDC / 200 mV/mil output is also accepted by the 3300 series legacy racks and by third-party monitors that conform to the same input specification, protecting the investment across platform upgrades.
• Sealed Housing for Harsh Environments: The IP67-equivalent housing allows installation in bearing pedestals, turbine enclosures, and compressor skids where condensation, lubricating oil mist, and process gas ingress are routine operating conditions.
• Reduced Spare-Parts Complexity: A single Proximitor model covers the majority of 3300 XL 8 mm probe installations, allowing maintenance teams to standardize their critical-spare inventory around one part number rather than managing multiple conditioner variants.
• Traceable Factory Calibration: Each unit ships with a factory calibration record tied to its serial number, providing the measurement chain documentation required for machinery protection system validation and insurance audits.

Quality Assurance & Global Logistics

Every 330850-90-05 unit dispatched from siemensplc.com is an original Bently Nevada (Baker Hughes) component sourced through verified supply channels. Units are stored in a climate-controlled warehouse in Xiamen, China, in anti-static, moisture-barrier packaging to preserve connector integrity and housing condition during storage. Pre-shipment inspection covers visual examination of the housing and connector, label and serial number verification, and connector pin-out continuity check. Certificates of conformance (CoC) and, where available, original factory test reports are provided with each shipment.

Xiamen’s position as a major international logistics hub — served by Xiamen Gaoqi International Airport and Xiamen Port — enables same-day or next-day handover to DHL Express, FedEx International Priority, and UPS Worldwide Expedited. Typical transit times are 3–5 business days to Europe and the Middle East, 4–7 business days to North America, and 2–4 business days to Southeast Asia. For urgent plant shutdowns or unplanned outages, expedited shipment with same-day dispatch is available for in-stock units ordered before 14:00 CST. All shipments include a commercial invoice, packing list, and CoC. Export classification and customs documentation are prepared in compliance with Chinese export regulations and destination-country import requirements.

A 12-month warranty covers manufacturing defects from the date of shipment. Warranty claims are processed with a target response time of 48 hours, and replacement units are dispatched from Xiamen stock where available.

Contact Information

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