The 330525 Velomitor XA Piezo-velocity Sensor is a ruggedized member of Bently Nevada’s Velomitor sensor family, specifically derived from the 330500 Velomitor Sensor. It is designed for machinery condition monitoring applications where a robust, weather-resistant, and highly reliable velocity transducer is required. The “XA” designation stands for eXtended Application, reflecting the sensor’s enhanced construction and suitability for installation in moist environments and other demanding industrial locations without the need for an additional protective housing. The sensor is built around a 316L stainless steel case and a unique weatherproof connector and cable assembly. When properly installed with a mating extension cable, the design meets IP-65 and NEMA 4X dust-rating requirements, making it suitable for outdoor and washdown-prone areas as well as conventional machine rooms.
The 330525 is intended to measure machine housing vibration in order to infer rotor vibration and overall machine dynamic behavior. Most common machine malfunctions, including imbalance, misalignment, and related faults, originate at the rotor and cause changes in rotor vibration. The location selected on the machine housing must accurately conduct rotor vibration to the transducer. Therefore, careful installation is essential. If the transducer is not installed correctly, it may not accurately detect vibration and can transmit invalid data. Bently Nevada provides engineering services to accurately measure machine housings and to install transducers, which helps ensure that the measurement point is suitable and that the sensor is mounted correctly.
The sensor is a piezo-velocity device with a sensitivity of 3.94 mV/mm/s (100 mV/in/s) ±5%. It provides a velocity output suitable for condition monitoring systems, and it is designed to operate over a very wide temperature range from -55°C to +121°C (-67°F to +250°F). Its hermetically sealed case, case-isolated grounding, and 316L stainless steel construction make it appropriate for harsh industrial environments. The 330525 is also available with agency approval options for hazardous area use, including CSA/NRTL/C and SIRA/CENELEC options. The product is supported by interconnect cables, terminal housings, bulk cable, terminal mounting blocks, and splash-resistant boot accessories, allowing a complete and maintainable installation to be configured for many plant environments.
Design and Construction
The 330525 Velomitor XA is a ruggedized version of the 330500 Velomitor Sensor. Its 316L stainless steel case provides corrosion resistance and mechanical durability, while the weatherproof connector and cable assembly permit mounting without a housing. This is a significant advantage in applications where an additional enclosure would increase installation cost, complicate maintenance, or interfere with the measurement path. The sensor cable assembly is suitable for use in moist environments, and the overall design meets IP-65 and NEMA 4X dust ratings when properly installed with a mating extension cable. The case is hermetically sealed, and the sensor can tolerate relative humidity to 100% non-submerged conditions. The connector is a 2-pin Mil-C-26482 hermetically sealed connector with a 316L stainless steel shell. The sensor weighs approximately 156 g (5.5 oz), has a diameter of 28 mm (1.1 in), and a height of 73.1 mm (2.88 in). The mounting interface includes a 1/4-18 NPT thread and a 25.4 mm (100 in thousandths notation in the drawing) hexagonal feature, as shown in the dimensional figure. The maximum mounting torque is 45 N-m (33 ft-lb). The cable bend radius should be no less than 1.5 inches.
The sensor polarity is defined such that Pin A goes positive with respect to Pin B when the sensor case motion is toward the connector. This polarity convention is important for consistent phase and signal interpretation in condition monitoring systems. The case is isolated, which helps avoid ground loops and supports reliable signal transmission in plant wiring. The dynamic output impedance is less than 2400 Ω, and the output bias voltage is -12 ±3.0 VDC over temperature, referenced to Pin A. Power requirements are -22 to -30 VDC with a bias current of 2.5 to 6.0 mA. These characteristics make the sensor compatible with typical Bently Nevada monitoring systems and suitable for long cable runs when the recommended cable is used. The datasheet states that a maximum cable length of 305 metres (1,000 feet) of Bently Nevada part number 02173007 can be used with no degradation of signal.
Measurement Principle and Machine Housing Considerations
The 330525 is a piezo-velocity sensor, meaning it produces an output proportional to velocity over its specified frequency range. Its sensitivity is 3.94 mV/mm/s (100 mV/in/s) ±5%. The frequency response is specified as 4.5 to 2,000 Hz (270 to 120,000 cpm) ±3.0 dB, and 6.0 to 1,000 Hz (360 to 60,000 cpm) ±0.9 dB. This response makes the sensor suitable for general machinery vibration monitoring, including rotating equipment where velocity is a commonly used indicator of overall vibration severity. The velocity range is 1270 mm/s (50 in/s) peak, and amplitude linearity is ±2% to 152 mm/s (6 in/s) peak. Transverse sensitivity is less than 5% of sensitivity, which helps ensure that the measurement is dominated by the intended axis. The mounted resonant frequency is greater than 12 kHz, providing adequate separation from the measurement bandwidth. The broadband noise floor from 4.5 Hz to 2 kHz is 0.004 mm/s (160 μin/s) rms, nominal, and the datasheet also lists broadband noise floor as less than 0.004 mm/s (160 μin/s). Temperature sensitivity is -14% to +7.5% typical over the operating temperature range, which is an important consideration when interpreting measurements over wide ambient temperature excursions.
Because the sensor is mounted on the machine housing, the user must consider how well the housing conducts rotor vibration to the transducer. Most common machine malfunctions originate at the rotor and cause a change in rotor vibration. The location selected on the housing must accurately conduct rotor vibration to the transducer. Installation should be carefully planned so that the sensor is mounted on a rigid, representative location with good mechanical contact. The datasheet warns that if the transducer is not installed carefully, it may not accurately detect vibrations and can transmit invalid data. Bently Nevada offers engineering services to accurately measure machine housings and to install transducers. This is particularly important for critical machinery, where a poor mounting location can lead to missed faults or false alarms. The sensor is typically mounted directly to the machine, and the mounting torque should not exceed 45 N-m (33 ft-lb). The cable should be routed with a minimum bend radius of 1.5 inches and should be supported to avoid strain on the connector.
Signal Interface and Cabling
The 330525 uses a 2-pin Mil-C-26482 hermetically sealed connector. The signal interface is a dynamic velocity output with a bias voltage of -12 ±3.0 VDC over temperature, referenced to Pin A. The dynamic output impedance is less than 2400 Ω. Power is supplied as -22 to -30 VDC with a bias current of 2.5 to 6.0 mA. The sensor case is isolated, which is important for avoiding ground loops and for maintaining signal integrity in industrial installations. The polarity convention is that Pin A goes positive with respect to Pin B when the sensor case motion is toward the connector. This should be observed when wiring the sensor to a monitor or data acquisition system.
Bently Nevada provides several cabling and termination options for the 330525. The 106765-AA Interconnect Cable is available in lengths from 1 meter (3.3 feet) to 25 meters (82 feet), ordered in increments of 3 meters. The 106769-AA Terminal Housing provides local connection of the Velomitor XA Sensor signal wires to the monitor field wiring. Each terminal housing can accommodate up to two Velomitor XA Sensor Cables. The terminal housing has conduit fitting options: 00 for no fittings supplied, 01 for one 3/4 NPT fitting, and 02 for two 3/4 NPT fittings. The 02173007 bulk cable is a two-conductor twisted, shielded 22 AWG cable without connectors or terminal lugs, ordered by length in feet. The datasheet states that up to 305 metres (1,000 feet) of 02173007 cable can be used with no degradation of signal. The 103537-01 Terminal Mounting Block provides simple field wiring connection and can be mounted inside any standard Proximitor Sensor housing; one terminal mounting block is needed for each Velomitor XA Sensor connection. The 03839144 splash-resistant boot cover is made from fluorosilicone elastomer and is blue; the 03839142 bottom clamp secures the boot to the Velomitor XA Sensor case, and the 03839143 top clamp secures the boot to the interconnect cable assembly. The cable assembly drawing shows stainless steel armor over the cable, 0.382 mm² (22 AWG) conductors, clear shrink tubing, “A” (white), “B” (black), and “SHLD” (green) identification, and an overall length tolerance of ±200 (7.8) in the drawing units.
Environmental and Hazardous Area Capability
The 330525 is designed for severe industrial environments. Its operating temperature range is -55°C to +121°C (-67°F to +250°F). It can survive shock levels of 5000 g peak, maximum. Relative humidity can be up to 100% non-submerged, and the case is hermetically sealed. The magnetic field susceptibility is less than 51 μm/s/gauss (based on 50 gauss, 50–60 Hz). The sensor is case-isolated, which supports flexible grounding arrangements. The weatherproof connector and cable assembly, together with the IP-65 and NEMA 4X rating when properly installed with a mating extension cable, allow the sensor to be used in moist environments without an additional housing. The datasheet warns that operating the unit outside the specified limits may result in false readings or loss of machine monitoring. Before installing and using the product, the user should read the 330500, 330525, and 330530 Velomitor Sensors User Guide (document 100076).
The 330525 is available with hazardous area approvals. For CSA/NRTL/C, the 330525 is listed as Ex ia IIC T4 and AEx ia IIC T4 for Class I, Division 1, Groups A, B, C, and D; Class II, Groups E, F, and G; and Class III. The temperature rating is T4 at -40°C ≤ Ta ≤ +100°C, and installation must be per drawing 167539 for the non-incendive version? The datasheet specifically shows for 330525: Ex ia IIC T4, AEx ia IIC T4, Class I Division 1 Groups A, B, C and D, Class II Groups E, F, G, Class III, T4 @ -40°C ≤ Ta ≤ 100°C; and Ex nL IIC T4, AEx nA IIC T4, Class I Division 2 Groups A, B, C, D, install per drawing 167539, T4 @ -40°C ≤ Ta ≤ 100°C. For ATEX/IECEx, the 330525 is covered by Ex 1 G Ex ia IIC T4 Ga; Ex 3 D Ex na IIC T4 Gc; Ex tc III T130°C Dc; T4 @ Ta = -55°C to 121°C. The entity parameters for the 330525 family, as listed with 330400, 330425, 330500, and 330525, include Zone 0/1 and Zone 2 values of Ui = 28 V and Ii = 150 mA. The conditions of safe use require that the equipment be connected to equipment meeting the listed entity parameters. Cables of type A or B in compliance with EN 60079-25 must respect the cable parameters listed with the entity parameters. For Zone 2, the supply electrical parameters shall not exceed the values in the tables. Detailed country and product-specific approvals are listed in the Approvals Quick Reference Guide (108M1756).
Compliance and Certifications
The 330525 complies with FCC Part 15 rules. Operation is subject to two conditions: the device may not cause harmful interference, and the device must accept any interference received, including interference that may cause undesired operation. The product is compliant with the EMC Directive 2014/30/EU and the RoHS Directive 2011/65/EU. The datasheet’s maritime section lists “330400 and 330425 only” for ABS 2009 Steel Vessels Rules references, so the maritime approval statement should be applied only to those models as indicated in the supplied datasheet. For hazardous area approvals, the detailed listing of country and product-specific approvals should be obtained from the Approvals Quick Reference Guide (108M1756) available from Bently.com. The product is supported by Bently Nevada documentation and technical support, and the user should refer to the 330500, 330525, and 330530 Velomitor Sensors User Guide (100076) before installation and use.
Ordering Information and Accessories
The 330525 ordering model is 330525-AA, where AA is the Agency Approval Option. The available options are 00 for None Required, 01 for CSA/NRTL/C, and 02 for SIRA/CENELEC. The 106765-AA Interconnect Cable is ordered by length in meters, with a minimum length of 1 meter (3.3 feet), a maximum length of 25 meters (82 feet), and ordering increments of 3 meters. The 106769-AA Terminal Housing is ordered with a conduit fitting option: 00 for no fittings supplied, 01 for one 3/4 NPT fitting, and 02 for two 3/4 NPT fittings. Each terminal housing can accommodate up to two Velomitor XA Sensor Cables. Accessories include the 100076 user guide for 330500/330525 Velomitor Sensor and Velomitor XA Sensor; 02173007 bulk cable, two-conductor twisted, shielded, 22 AWG cable without connectors or terminal lugs, specified by length in feet; 103537-01 Terminal Mounting Block, which provides simple field wiring connection and can be mounted inside any standard Proximitor Sensor housing, with one terminal mounting block needed for each Velomitor XA Sensor connection; 03839144 splash-resistant boot cover for the interconnect cable assembly, made from fluorosilicone elastomer and blue in color; 03839142 bottom clamp used to secure the boot to the Velomitor XA Sensor case; and 03839143 top clamp used to secure the boot to the interconnect cable assembly. These accessories allow the user to build a complete installation with appropriate strain relief, environmental protection, and field termination.
Applications and Benefits
The 330525 is suitable for a wide range of machinery condition monitoring applications where a rugged velocity sensor is needed. Its 316L stainless steel case and weatherproof connector/cable assembly permit mounting without a housing, reducing installation complexity and cost. The sensor is suitable for moist environments and meets IP-65 and NEMA 4X dust ratings when properly installed with a mating extension cable. Its wide operating temperature range of -55°C to +121°C supports use in hot and cold climates, and its 5000 g shock survivability provides margin against handling and installation shocks. The case-isolated design, 2-pin Mil-C-26482 connector, and compatibility with Bently Nevada interconnect cables and terminal housings simplify integration with monitoring systems.
The sensor’s velocity output and frequency response make it useful for detecting common machine faults such as imbalance, misalignment, looseness, and other rotor-related problems that manifest in housing vibration. The broadband noise floor and transverse sensitivity specifications support reliable measurement in typical industrial environments. The availability of CSA/NRTL/C and SIRA/CENELEC approval options allows the sensor to be applied in hazardous areas when installed according to the applicable drawings and entity parameters. The range of accessories, including the splash-resistant boot, terminal housing, terminal mounting block, and bulk cable, allows users to configure a complete installation that protects the connector and cable while providing convenient field termination. Because the sensor is a ruggedized version of the 330500 Velomitor, users familiar with Bently Nevada Velomitor technology can apply the 330525 with a similar measurement principle while gaining the extended application benefits of the XA construction.
Installation and Maintenance Considerations
Careful installation is essential for reliable measurement. The sensor should be mounted on a rigid machine housing location that accurately conducts rotor vibration to the transducer. The mounting torque should not exceed 45 N-m (33 ft-lb). The cable should be routed with a minimum bend radius of 1.5 inches, and strain relief should be provided so that the connector is not subjected to excessive force. The polarity convention should be observed: Pin A goes positive with respect to Pin B when the sensor case motion is toward the connector. The case is isolated, and the dynamic output impedance is less than 2400 Ω. Power should be supplied within -22 to -30 VDC and the bias current should be within 2.5 to 6.0 mA. When using long cable runs, the recommended 02173007 cable can be used up to 305 metres (1,000 feet) with no degradation of signal. The user should read the 330500, 330525, and 330530 Velomitor Sensors User Guide (document 100076) before installing and using the product. Operating the unit outside the specified limits may result in false readings or loss of machine monitoring. For hazardous area installations, the equipment must be connected to equipment meeting the listed entity parameters, and cables of type A or B in compliance with EN 60079-25 must respect the cable parameters. Zone 2 supply electrical parameters shall not exceed the values listed in the approval tables. Detailed country and product-specific approvals should be confirmed in the Approvals Quick Reference Guide (108M1756).
