June 06, 2026

Bently Nevada 18745-03 Proximitor Product Specification

18745-03 is a universal calibrated eddy-current proximitor belonging to Bently Nevada classic 7200 transducer family, manufactured in the United States as the core signal conditioning component of a complete three-piece proximity sensor system consisting of proximity probe, extension cable and proximitor unit. Unlike model 18745-01 dedicated exclusively to 5 mm probes and 18745-04 customized for high-temperature 8 mm probe applications, this unit receives factory dual calibration to support both standard 5 mm and 8 mm diameter proximity probes, making it the most widely used general-purpose spare part for equipment maintenance and field retrofitting across global power, petrochemical and metallurgical industries. Following eddy-current induction principles, it converts physical clearance variation between the probe tip and conductive rotating target into proportional linear negative DC voltage output, feeding processed signals into Bently 3300, 3500 rack monitors, local panel indicators and plant DCS/PLC systems to realize continuous shaft vibration, axial thrust displacement and differential expansion monitoring as well as equipment safety protection complying with API 670 industry specification.

Description

Bently Nevada 18745-03 Proximitor Product Specification

1. General Product Overview

2. Matching Sensor System Configuration

Factory dual calibration enables 18745-03 to flexibly mate with either 330101 series 5 mm probes or 330102 series 8 mm probes paired with corresponding 330130 coaxial extension cables. The total combined cable length of probe plus extension cable is fixed and pre-calibrated during factory production; common standard preset lengths include 5 meters and 9 meters. Random field cutting or arbitrary replacement of unmatched probes or extension cables will alter system total capacitance, resulting in shifted sensitivity and degraded linear measurement accuracy. Interconnection between probe tail and extension cable adopts gold-plated ClickLoc quick-lock connectors with excellent anti-humidity and anti-corrosion performance, maintaining stable signal transmission under damp and mildly corrosive industrial cabinet environments. No internal hardware modification is required on the proximitor when switching between 5 mm and 8 mm probe assemblies at site.

3. Key Electrical Performance Parameters

The proximitor accepts standard negative DC supply ranging from -18 VDC to -24 VDC, with -24 VDC recommended as nominal operating voltage. Its factory-set fixed sensitivity is 200 mV/mil, equivalent to 7.87 V per millimeter of gap change between probe and target surface, consistent with the unified specification of the full 18745 series. Standard effective linear measuring range covers 80 mils, approximately 2 millimeters of valid clearance window, with full-scale linearity error controlled below 1% of full span to guarantee precise measurement of static shaft position offset and dynamic vibration fluctuation. The frequency response spans from DC (0 Hz) up to 10 kHz, allowing simultaneous acquisition of steady-state axial displacement and high-frequency radial shaft vibration, rotor eccentricity and Keyphasor reference pulse signals without waveform distortion.

Output voltage changes linearly from near 0 VDC to -24 VDC across the full calibrated gap range. Test terminals are reserved on the terminal block to facilitate regular on-site calibration and circuit troubleshooting without shutting down running production machinery. Built-in internal protection circuits including transient surge suppression, overvoltage clamping and short-circuit prevention shield onboard electronics against damage caused by field wiring errors and instantaneous power grid fluctuation. Total operating power consumption remains low to avoid excessive heat buildup inside sealed compact control cabinets.

4. Mechanical Structure and Mounting Details

Constructed with flame-retardant high-strength industrial plastic housing, the 18745-03 shares identical outer dimensions with other 18745 variants at 81.3 mm height × 61.2 mm width × 63.5 mm depth and roughly 220 grams net weight. Two installation options are available: standard DIN top-hat rail snap mounting inside control cabinets or direct fixed mounting onto equipment panels via screw fasteners, enabling direct interchangeable replacement for 18745-01 and 18745-04 during spare part swap without cabinet mechanical alteration. A single power status LED is arranged on the front panel to display energization condition; screw-type terminal blocks on the lower side are clearly marked for power input, probe coaxial signal input and analog output wiring to minimize field connection mistakes. The printed circuit board receives full conformal coating to resist dust, moisture and mild corrosive industrial gas inside control room environments, and the enclosure carries an IP20 protection rating suitable only for indoor cabinet installation rather than open-air exposed locations.

5. Environmental Operating Specifications

Continuous rated working ambient temperature extends from -20°C to +70°C for regular indoor cabinet installation; short-term intermittent operation can tolerate ambient temperature ranging from -40°C up to +85°C to adapt occasional harsh field surroundings near warm machinery casings. Storage and transportation temperature covers -40°C to +125°C to accommodate cross-regional spare part shipment and long-term warehouse storage under variable extreme climate conditions. Permitted relative operating humidity is limited between 5% and 95% under non-condensing ambient conditions to prevent internal PCB short-circuit triggered by cabinet dew accumulation and damp air.

6. Industrial Application Range

Thanks to its dual-probe compatible design, 18745-03 serves as universal replacement for both 5 mm and 8 mm proximity measurement loops on steam turbines, gas turbines, centrifugal compressors, large feed pumps, induced draft fans and generators in thermal power plants, petrochemical refineries, natural gas compression stations and metallurgical facilities. It monitors critical parameters including radial shaft vibration, axial thrust position and rotor differential expansion to capture early equipment faults such as shaft rub, bearing wear and rotor misalignment. When measured values exceed user-defined Alert and Danger thresholds, the monitoring system triggers local alarm indication or emergency trip interlock to protect high-value rotating equipment from catastrophic damage. Combined with Keyphasor sensors, it also provides rotational speed and phase reference data for rotor dynamic analysis and predictive maintenance trending.

7. Certification and Warranty Provisions

Original genuine 18745-03 complies with Bently Nevada internal factory quality standards, CE electrical safety certification and API 670 international rotating machinery protection requirements; factory calibration documents can be provided upon customer request for incoming inspection purposes. When installed and wired strictly within specified electrical and environmental operating limits without artificial physical damage, reverse polarity power connection or overvoltage abuse, the unit is covered by a twelve-month limited manufacturer warranty starting from goods delivery date, covering inherent manufacturing defects of internal electronic components and circuit assembly. Hazardous-area certified versions meeting Class I Division 2 standards are available via special pre-order for installation inside classified explosive gas industrial sites.

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