Bently Nevada 330500-00-02 Velomitor Piezo-velocity Sensor

The Bently Nevada 330500-00-02 is a specific configuration of the field‑proven 330500 Velomitor Piezo‑velocity Sensor, engineered for critical machinery monitoring applications requiring ATEX (European) certification for use in potentially explosive atmospheres, while offering maximum mounting flexibility by excluding a factory‑supplied thread adapter. This variant features no mounting adapter (suffix -00), leaving the sensor’s native 3/8‑24 UNF‑2B body thread exposed, and carries ATEX certification (suffix -02), making it suitable for installation in European and international hazardous (classified) locations where intrinsic safety is required under the ATEX Directive 2014/34/EU. It is the ideal choice for users who have existing mounting holes matching the 3/8‑24 thread, who prefer to use custom adapters, or who want to avoid the cost of a pre‑installed adapter while still meeting ATEX safety standards.

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 330500-00-02 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 -00-02 variant is supplied without a mounting adapter, but carries ATEX certification for Ex ia IIC T3 Ga (intrinsic safety for Zone 0/1), Ex ec IIC T3 (increased safety for Zone 2), and Ex tc IIC T200°C Dc (dust protection for Zone 22), with entity parameters that enable intrinsic safety operation.

This introduction focuses exclusively on the 330500-00-02 configuration, highlighting its unique combination of ATEX certification and adapter‑free mounting flexibility, comparing it with other adapter options (e.g., 330500-01-02 with 1/2‑20 UNF adapter) and with non‑certified versions (e.g., 330500-00-00) to guide proper selection for hazardous‑area applications where custom or existing mounting solutions are preferred.

Functional Description and ATEX Certification Significance

The 330500-00-02 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 330500-00-02 is designed to be mounted directly on the machine casing or bearing housing using the body thread. The standard sensor body incorporates a 3/8‑24 UNF‑2B mounting hole, which is a common thread size for many industrial mounting bases and adapters. By choosing the -00 adapter option, the user receives the sensor without a pre‑installed adapter, offering maximum flexibility to select a third‑party adapter or to mount the sensor directly into a threaded hole that matches the body thread.

The -02 certification adds ATEX approval for use in hazardous locations under European and international regulations. The sensor carries the following ATEX markings (as per the datasheet):

• Ex ia IIC T3 Ga – Intrinsic safety for Zone 0 (continuous presence of explosive gas) and Zone 1, suitable for Gas Group IIC (hydrogen, acetylene) and T3 temperature class (≤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.

Additionally, the sensor meets the entity parameters for intrinsic safety (when connected through an approved barrier): Ui = 28 V, Ii = 100 mA, Pi = 0.84 W, Ci = 10.8 nF, Li = 0 μH. These parameters are critical for selecting an appropriate intrinsic safety barrier and for ensuring compliance with EN 60079‑25 (cable parameter requirements).

The ATEX certification is mandatory for installations in Europe and is widely accepted in many other regions that follow IECEx or ATEX standards. By choosing the -02 option, users can deploy the 330500 in hazardous areas with confidence, ensuring safety and regulatory compliance without the need for additional certification.

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 330500-00-02 with other common configurations: the 330500-00-00 (no adapter, no approvals), the 330500-01-02 (1/2‑20 UNF adapter, ATEX), the 330500-00-01 (no adapter, CSA), and the 330500-01-04 (1/2‑20 UNF adapter, multiple approvals). This comparison highlights the unique value of the -00-02 for flexible, ATEX‑certified installations.

Selection Guide – Key Differences

The 330500-00-02 is the most flexible ATEX‑certified configuration in the 330500 series. Choose this variant when:

• You need ATEX certification for hazardous locations in Europe or other regions accepting ATEX.

• You have an existing mounting hole that matches the 3/8‑24 UNF‑2B thread, or you plan to use a custom adapter not offered by Bently Nevada.

• You want to minimize cost by omitting the adapter while still meeting safety requirements.

• You prefer the body thread for direct mounting without an extra adapter.

If you need a specific adapter (e.g., 1/2‑20 UNF for quick‑connect mounts) with ATEX, choose 330500-01-02. If you require CSA certification instead of ATEX, choose 330500-00-01. For multiple approvals, choose 330500-01-04.

Hardware Characteristics – Specific to 330500-00-02

Physical Dimensions and Mounting

• Body Thread (exposed): 3/8‑24 UNF‑2B, with a minimum threaded depth of 6.4 mm (0.250 in) and a maximum drill depth of 14.0 mm (0.550 in). The sensor body includes a 15/16 inch hexagonal feature for tightening.

• Diameter: 25.3 mm (0.995 in)

• Height: 63.2 mm (2.49 in) (without adapter; with an adapter, the height increases)

• Weight: 142 grams (5.0 oz) typical (without adapter)

• Case Material: 316L stainless steel, hermetically sealed

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

• Mounting Torque: 32‑46 kg·cm (24‑40 in‑lb) maximum (for the sensor body when tightened into a mounting hole)

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 330500-00-02 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 EN 60079‑25. 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.

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)

ATEX Hazardous Area Compliance – Detailed for 330500-00-02

The 330500-00-02 is certified to the following ATEX standards (as per the datasheet):

• Ex ia IIC T3 Ga – 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 – For Zone 2 (increased safety).

• Ex tc IIC T200°C Dc – For Zone 22 (dust protection).

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

Entity Parameters (for intrinsic safety, identical for Zone 0/1 and Zone 2):

Conditions of Safe Use (per ATEX/IECEx):

• For Zone 0/1: 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) must be used, respecting cable capacitance and inductance limits.

• For Zone 2: The supply electrical parameters shall not exceed the values mentioned in the table above.

• The mating connector must provide at least IP54 ingress protection as required by EN 60079‑0 and EN 60079‑7/15.

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

Installation Best Practices for 330500-00-02 in ATEX‑Certified Installations

1. Intrinsic Safety Barrier – Always connect the sensor through an ATEX‑certified intrinsic safety barrier that limits voltage, current, and power to within the entity parameters. 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. For long runs, use lower‑capacitance cables (e.g., 18 AWG) to maximize allowable length. Consult the barrier manufacturer’s documentation for cable length calculations and ensure cable type A or B per EN 60079‑25.

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 3/8‑24 UNF‑2B thread and is perpendicular to the measurement axis. Apply anti‑seize compound if required, and torque the 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 15/16 inch hex flats.

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 ATEX‑Certified Options – Why Choose 330500-00-02?

• vs. 330500-01-02 (with 1/2‑20 UNF adapter) – The -01-02 includes a 1/2‑20 UNF adapter, which is convenient for quick‑connect mounts (e.g., 46122-01). If you do not need this specific adapter, the -00-02 saves cost and provides the flexibility to use any adapter you choose, or to mount directly into a 3/8‑24 hole.

• vs. 330500-00-00 (no approvals) – The -00-00 lacks ATEX certification. For any European hazardous area installation, the -02 (ATEX) version is mandatory. The -00-02 provides the same mounting flexibility but adds critical safety compliance.

• vs. 330500-00-01 (CSA) – The -01 offers CSA certification for North America. If your installation is in Europe and requires ATEX, choose -02. If you need both, consider -04 (multiple approvals).

• vs. 330500-01-04 (multiple approvals with adapter) – The -04 includes both CSA and ATEX, plus a 1/2‑20 adapter. If you don’t need the adapter or only need ATEX, the -00-02 is more economical.

Ordering Information

When ordering the 330500-00-02, use the full part number exactly as shown:

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

• -00 – Mounting Thread Adapter: None (body thread 3/8‑24 UNF‑2B exposed)

• -02 – Agency Approval: ATEX (European)

Compatible Cables and Accessories for Hazardous Areas

Note: The 330500-00-02 does not include a cable or adapter; order separately. Ensure cables and barriers are ATEX‑certified for hazardous area use.

Certifications and Compliance – Special Note

The 330500-00-02 carries ATEX certification for European hazardous locations. 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 CSA or IECEx; for those, select -01 or -04 options.

Warranty and Support

The Bently Nevada 330500-00-02 is covered under the standard manufacturer’s warranty. For technical support, application assistance, or help with ATEX certification documentation, contact your local Bently Nevada representative or access the Bently Nevada Media Library at bntechsupport.com.