Bently Nevada 330500-04-04 Velomitor Piezo-velocity Sensor

The Bently Nevada 330500-04-04 is the definitive global‑ready, coarse‑threaded configuration of the 330500 Velomitor Piezo‑velocity Sensor, engineered for critical machinery monitoring in hazardous locations worldwide where both CSA (North America) and ATEX (Europe) certifications are required, while also offering the universal convenience of a 1/4‑20 UNC coarse‑thread adapter for compatibility with a wide range of general‑purpose mounting hardware. This variant carries multiple approvals (suffix -04) and is equipped with a 1/4‑20 UNC mounting adapter (suffix -04), making it the ultimate choice for global OEMs, EPCs, and end‑users who need a single sensor part number that meets both North American and European intrinsic safety requirements, while benefiting from the coarse thread that offers fast installation, universal availability, and excellent tolerance for field conditions—particularly valuable in portable and temporary monitoring applications across multiple regulatory regions.

The 330500 series is a state‑of‑the‑art piezoelectric velocity sensor with embedded integrated electronics, designed to measure absolute (relative to free space) bearing housing, casing, or structural vibration on rotating machinery. Unlike traditional velocity transducers that rely on moving coils and mechanical springs, the 330500 employs a solid‑state design with no moving parts, offering superior reliability, extended service life, and the ability to be mounted in any orientation—vertically, horizontally, or at any angle—without performance degradation.

The 330500-04-04 provides a velocity output of 100 mV/in/s (3.94 mV/mm/s) with a frequency response from 4.5 Hz to 5 kHz (±3 dB) and a velocity range of 50 in/s peak (1270 mm/s) . Its robust construction includes a hermetically sealed 316L stainless steel case, a 2‑pin MIL‑C‑5015 connector, and a wide operating temperature range from -55°C to +121°C. The sensor is case‑isolated to prevent ground loops, and it offers excellent immunity to magnetic fields and base strain. The -04-04 variant is supplied with a 1/4‑20 UNC adapter already threaded onto the body, ready for immediate installation using standard 1/4‑20 mounting hardware, and carries both CSA and ATEX certifications, making it suitable for Class I, Division 1, Groups A, B, C, D; Class II, Groups E, F, G; and Class III hazardous locations (CSA) as well as Zone 0, Zone 1, Zone 2, and Zone 22 (ATEX) with entity parameters that enable intrinsic safety operation.

This introduction focuses exclusively on the 330500-04-04 configuration, highlighting its unique value as the only coarse‑threaded, dual‑certified Velomitor in the Bently Nevada portfolio. It compares this variant with other adapter options (e.g., -00-04 with no adapter, -01-04 with 1/2‑20 UNF, -02-04 with M8 x 1, -03-04 with 1/4‑28 UNF) and with single‑certification versions (e.g., -04-01 for CSA, -04-02 for ATEX) to guide proper selection for global hazardous‑area applications where coarse‑thread mounting convenience and multi‑region compliance are paramount.

Functional Description and the Advantage of Dual Certification with 1/4‑20 UNC Coarse‑Thread Mounting

The 330500-04-04 accelerometer operates on the piezoelectric principle, where a piezoelectric crystal generates an electrical charge proportional to the acceleration of the sensor housing. An internal charge amplifier and integrator circuit convert this acceleration signal into a velocity signal, which is then output as a low‑impedance voltage. The output bias voltage is nominally -12 V dc (referenced to Pin A), which allows the sensor to be powered by the same two‑wire interface used for many industrial monitoring systems. The sensor requires a power supply of -24 V dc (nominal) and draws a bias current of 2 mA (typical), with the dynamic signal superimposed on the bias voltage.

The integration of the electronics within the sensor housing eliminates the need for external signal conditioning, simplifies installation, and reduces the risk of noise pickup. The solid‑state design ensures that there are no moving parts to wear out, providing long‑term stability and repeatability. The 330500-04-04 is designed to be mounted directly on the machine casing or bearing housing using the supplied adapter. The 1/4‑20 UNC thread is a coarse‑pitch thread (20 threads per inch) that is one of the most widely used and universally available thread standards in the United States and many other regions. It is commonly found on a vast array of mounting hardware, including studs, bolts, and threaded holes in machinery casings. The coarse pitch offers several practical advantages in global hazardous area installations: it is less susceptible to cross‑threading when working in confined spaces or with gloves, allows for faster installation and removal (critical for maintenance in hazardous zones), provides greater tolerance for dirt, corrosion, and debris on threads, and offers excellent holding power for the sensor under vibration. Unlike fine threads, which require precise alignment and careful torque control, the 1/4‑20 UNC thread is forgiving and user‑friendly, making it a preferred choice for field installations where speed and reliability are essential.

The -04 certification adds both CSA and ATEX approvals, making it a truly global solution. The sensor carries the following markings (as per the datasheet):

• CSA: Class I, Division 1, Groups A, B, C, D; Class II, Groups E, F, G; Class III; Temperature Class T3; -55°C ≤ Tamb ≤ +121°C.

• ATEX: Ex ia IIC T3 Ga (Zone 0/1), Ex ec IIC T3 (Zone 2), Ex tc IIC T200°C Dc (Zone 22); -55°C ≤ Ta ≤ +121°C.

Entity Parameters (identical for both certifications):

The dual certification eliminates the need to stock separate sensors for North American and European hazardous areas, simplifying inventory management and reducing the risk of using the wrong sensor in a given location. For global OEMs, EPCs, and end‑users with facilities on multiple continents, the 330500-04-04 offers a single part number that meets the most common intrinsic safety requirements worldwide, while the 1/4‑20 UNC adapter ensures compatibility with standard general‑purpose mounting hardware.

The combination of the 1/4‑20 UNC adapter and dual certifications makes the 330500-04-04 a versatile, safe, and convenient transducer for global hazardous areas. It eliminates the need for a separate adapter purchase, saving time and reducing potential installation errors. The adapter is factory‑installed and properly torqued, ensuring a reliable mechanical connection. This configuration is particularly valuable for maintenance teams who frequently use general‑purpose mounting hardware or need to install sensors quickly in hazardous areas across different regions, as the coarse thread allows for rapid engagement and disengagement even with gloved hands or in low‑visibility conditions, and the sensor can be used in both North American and European hazardous locations without requiring different sensors.

The sensor’s frequency response covers the range from 4.5 Hz to 5 kHz (270 cpm to 300,000 cpm) within ±3 dB, and from 6.0 Hz to 2.5 kHz (360 cpm to 150,000 cpm) within ±0.9 dB. This wide bandwidth makes it suitable for both low‑speed and high‑speed machinery, including gearboxes and turbines with high blade‑pass frequencies. The velocity output is particularly advantageous for machinery protection because it provides a direct measure of vibration severity, which is often the parameter used in international standards (e.g., ISO 10816) for evaluating machine health.

The sensor's amplitude linearity is ±2% up to 6 in/s peak, and its transverse sensitivity is less than 5% of the axial sensitivity. The mounted resonant frequency exceeds 12 kHz, ensuring that the sensor's natural resonance does not interfere with the measurement band. The case‑isolated design prevents ground loops, and the hermetically sealed construction protects the electronics from moisture and contaminants.

Detailed Comparison with Other 330500 Configurations – Adapter and Approval Options

To assist in proper sensor selection, the following table compares the 330500-04-04 with other common configurations: the 330500-04-00 (1/4‑20 UNC adapter, no approvals), the 330500-00-04 (no adapter, dual approvals), the 330500-01-04 (1/2‑20 UNF adapter, dual approvals), the 330500-02-04 (M8 x 1 adapter, dual approvals), the 330500-03-04 (1/4‑28 UNF adapter, dual approvals), the 330500-04-01 (1/4‑20 UNC adapter, CSA), and the 330500-04-02 (1/4‑20 UNC adapter, ATEX). This comparison highlights the unique value of the -04-04 for coarse‑thread, dual‑certified applications.

Selection Guide – Key Differences

The 330500-04-04 is the only coarse‑threaded, dual‑certified configuration in the 330500 series. Choose this variant when:

• You need both CSA and ATEX certifications for global hazardous area deployments.

• You prefer the 1/4‑20 UNC coarse thread for its universal availability, ease of installation, and tolerance for field conditions.

• You want a factory‑installed, properly torqued adapter for reliable mechanical connection.

• You want to avoid the hassle of sourcing and installing a separate adapter.

If you need a different adapter (e.g., 1/2‑20 for heavier mounts, M8 for metric, 1/4‑28 for fine thread) with dual approvals, choose -01-04, -02-04, or -03-04. If you only need CSA or ATEX individually, choose -04-01 or -04-02 respectively.

Hardware Characteristics – Specific to 330500-04-04

Physical Dimensions and Mounting

• Adapter Thread: 1/4‑20 UNC (male), installed on the sensor body. The adapter is made of stainless steel and is factory‑torqued for reliable performance.

• Sensor Body Thread (under adapter): 3/8‑24 UNF‑2B (factory default).

• Height (with adapter): 63.2 mm (2.49 in) + additional height for the adapter (approx. 4‑6 mm, total ~67‑69 mm).

• Diameter: 25.3 mm (0.995 in)

• Weight: 142 grams (5.0 oz) typical (without adapter); with adapter, slightly heavier.

• Case Material: 316L stainless steel, hermetically sealed

• Connector: 2‑pin MIL‑C‑5015 hermetically sealed receptacle, 316L stainless steel shell

• Mounting Torque for Adapter: 32‑46 kg·cm (24‑40 in‑lb) maximum (torque applied to the adapter when mounting the sensor onto the machine).

Polarity and Wiring

The sensor has a 2‑pin connector. The pin assignment is:

• Pin A: Signal + (positive output when the sensor case moves toward the connector)

• Pin B: Common (return) and power supply negative (shield)

The output bias voltage is -12 V dc (±3 V) referenced to Pin A. The sensor requires a -24 V dc supply (nominal) with a bias current of 2 mA (typical). The dynamic signal is a velocity output superimposed on the bias voltage.

Cables and Maximum Length

The 330500-04-04 is compatible with the same two‑conductor shielded cables as all 330500 variants. For hazardous area installations, the cable must be suitable for intrinsic safety and must meet the entity parameter limits per both CSA and ATEX requirements. The recommended cable (part number 02173006) is 18 AWG twisted shielded bulk cable. For pre‑terminated cables, the following options are available (custom lengths in 1.0 ft increments):

Maximum cable length: 305 meters (1,000 ft) of cable (part number 02173006) with no signal degradation, provided the cable capacitance is within limits. For longer lengths, contact Bently Nevada Tech Support. The recommended cable length for a 50 g vibration at 10 kHz and cable capacitance of 200 pF/m is 208 ft (63 m). In hazardous areas, cable capacitance and inductance must be added to the sensor's Ci and Li, and the total must not exceed the barrier's limits for both CSA and ATEX.

Environmental and Electrical Specifications

• Power Requirements: -24 V dc nominal, 2 mA bias current typical

• Output Bias Voltage: -12 V dc ±3 V

• Dynamic Output Impedance: < 2400 Ω

• Operating Temperature: -55°C to +121°C (-67°F to +250°F)

• Shock Survivability: 5,000 g peak maximum

• Relative Humidity: 100% condensing (non‑submerged); case is hermetically sealed

• Base Strain Sensitivity: 0.005 in/s/mstrain (very low, minimising errors from mounting surface flexure)

• Magnetic Field Susceptibility: < 51 in/s/gauss at 50 gauss, 50‑60 Hz

• Grounding: Case isolated (housing isolated from signal common)

Hazardous Area Compliance – CSA and ATEX Dual Certification

The 330500-04-04 is certified to both CSA and ATEX standards, as detailed below.

CSA Certification (North America):

• Class I, Division 1, Groups A, B, C, D (flammable gases/vapors)

• Class II, Groups E, F, G (combustible dusts)

• Class III (ignitable fibers/flyings)

• Temperature Class T3, with ambient temperature range -55°C ≤ Tamb ≤ +121°C.

• Install per drawing 167537.

ATEX Certification (Europe):

• Ex ia IIC T3 Ga – Intrinsic safety for Zone 0 (continuous presence of explosive gas) and Zone 1, Gas Group IIC (hydrogen, acetylene), Temperature Class T3 (≤200°C surface temperature).

• Ex ec IIC T3 – Increased safety for Zone 2.

• Ex tc IIC T200°C Dc – Dust protection for Zone 22.

• Ambient temperature range: -55°C ≤ Ta ≤ +121°C.

Entity Parameters (identical for both):

Conditions of Safe Use:

• For Zone 0/1 (ATEX) and Division 1 (CSA): The sensor must be connected to an associated intrinsically safe apparatus that meets the entity parameters. Cable type A or B per EN 60079‑25 (for ATEX) and appropriate cable parameters for CSA must be respected.

• For Zone 2 (ATEX) and Division 2 (CSA): The supply electrical parameters shall not exceed the values in the table above.

• The mating connector must provide at least IP54 ingress protection per applicable standards.

• Transient protection shall be provided at a level not exceeding 140% of the peak rated voltage.

The dual certification allows the same sensor to be used in hazardous areas under both North American and European regulatory frameworks, simplifying logistics and reducing the risk of using uncertified equipment.

Installation Best Practices for 330500-04-04 in Global Hazardous Areas

1. Intrinsic Safety Barrier – Always connect the sensor through a certified intrinsic safety barrier that meets the requirements of both CSA and ATEX (if used in respective jurisdictions). Ensure the barrier’s output parameters (Uo, Io, Po) do not exceed Ui, Ii, and Pi.

2. Cable Selection and Length Calculation – The sensor’s Ci (10.8 nF) and Li (0 μH) must be added to the cable’s capacitance and inductance. The total must not exceed the barrier’s allowable cable parameters. Consult the barrier manufacturer’s documentation and ensure compliance with both CSA and ATEX cable parameter limits.

3. Mounting Surface Preparation – Clean the mounting surface to remove paint, rust, or debris. Achieve a surface finish of 32 µin rms or better. Ensure the threaded hole matches the 1/4‑20 UNC thread and is perpendicular to the measurement axis. Apply anti‑seize compound if required, and torque the adapter (or sensor body) to 32‑46 kg·cm (24‑40 in‑lb). Do not use the connector body to apply torque; use a wrench on the hex flats of the adapter or the 15/16 inch hex flats of the sensor body.

4. Cable Connection – Align the 2‑pin connector (Pin A and Pin B) and tighten the coupling nut securely. In hazardous areas, ensure the connector is properly mated and sealed (IP54 or better) to prevent ingress.

5. Grounding – The case is isolated, so grounding is not required for the sensor body. However, the cable shield should be grounded at the power supply end (typically at the barrier) to minimize noise. Do not ground the shield at both ends to avoid ground loops.

6. Environmental Protection – Although the sensor is IP68, the cable termination and connectors require additional protection (splash boots, conduit, etc.) for outdoor or wet locations.

Comparison with Other Dual‑Certified Options – Why Choose 330500-04-04?

• vs. 330500-04-00 (1/4‑20, no approvals) – The -04-00 is for safe areas only. If your installation is in a hazardous area, the -04-04 is mandatory for compliance. The -04-04 provides the same coarse‑thread convenience but adds critical safety certifications (both CSA and ATEX).

• vs. 330500-00-04 (no adapter, dual approvals) – The -00-04 offers the same certifications but without a pre‑installed adapter. If you have a custom mounting hole that matches the 3/8‑24 body thread or you want to use a different adapter, the -00-04 is more flexible. However, if you want a ready‑to‑mount 1/4‑20 UNC adapter for general‑purpose hardware, the -04-04 saves time and ensures proper torque.

• vs. 330500-01-04 (1/2‑20 adapter, dual approvals) – The -01-04 is for larger fine‑thread mounts. If your mounting hardware uses 1/4‑20 (coarse, smaller, more universal), choose -04-04. If 1/2‑20, choose -01-04. The 1/4‑20 is more common for general‑purpose hazardous area installations.

• vs. 330500-02-04 (M8 adapter, dual approvals) – The -02-04 is for metric thread. If your machinery uses metric, choose -02-04; if you use imperial coarse thread (1/4‑20), choose -04-04.

• vs. 330500-03-04 (1/4‑28 adapter, dual approvals) – Both are 1/4‑inch diameter, but the -03-04 is fine thread (28 TPI) while the -04-04 is coarse thread (20 TPI). Choose -04-04 for faster installation, better tolerance for dirt/debris, and easier handling in hazardous areas; choose -03-04 for precision applications requiring fine adjustment.

• vs. 330500-04-01 (1/4‑20, CSA only) – The -04-01 is only CSA‑certified. If you need both CSA and ATEX (e.g., equipment may be deployed in Europe or North America), the -04-04 is the better choice, eliminating the need for two separate part numbers.

• vs. 330500-04-02 (1/4‑20, ATEX only) – The -04-02 is only ATEX‑certified. If you need both, the -04-04 provides a single solution for global projects.

Ordering Information

When ordering the 330500-04-04, use the full part number exactly as shown:

• 330500 – Base model (Velomitor Piezo‑velocity Sensor)

• -04 – Mounting Thread Adapter: 1/4‑20 UNC

• -04 – Agency Approval: Multiple (CSA, ATEX)

Compatible Cables and Accessories for Hazardous Areas

Note: The 330500-04-04 includes the 1/4‑20 UNC adapter and does not include a cable. Ensure cables and barriers are certified for both CSA and ATEX if used in respective jurisdictions.

Certifications and Compliance – Special Note

The 330500-04-04 carries both CSA and ATEX certifications, making it compliant with North American and European hazardous area requirements. It also complies with FCC Part 15, EMC Directive 2014/30/EU, RoHS Directive 2011/65/EU, China RoHS (EFUP 15 years), and ABS Marine. It is NOT certified to IECEx separately, but ATEX is harmonized with IECEx; for IECEx specific requirements, consult the factory.

Warranty and Support

The Bently Nevada 330500-04-04 is covered under the standard manufacturer’s warranty. For technical support, application assistance, or help with certification documentation, contact your local Bently Nevada representative or access the Bently Nevada Media Library at bntechsupport.com.