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

The Bently Nevada 330500-00-00 is a specific configuration of the field‑proven 330500 Velomitor Piezo‑velocity Sensor, designed for critical machinery monitoring applications where direct velocity output is required and no agency approvals (non‑hazardous area) are needed. This variant features no mounting thread adapter (suffix -00) and carries no hazardous area certifications (suffix -00), making it the most basic and cost‑effective version of the 330500 series. It is ideal for installations in safe (non‑classified) industrial environments where the sensor’s native 3/8‑24 UNF‑2B mounting thread is compatible with existing mounting hardware or where a custom adapter will be field‑installed.

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 330500-00-00 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 -00-00 variant is supplied without a mounting adapter, leaving the sensor’s body thread (3/8‑24 UNF‑2B) exposed for direct mounting or for field installation of a custom adapter.

This introduction focuses exclusively on the 330500-00-00 configuration, highlighting its unique “bare” mounting approach, comparing it with other adapter options (e.g., 330500-01-00 with 1/2‑20 UNF, 330500-03-00 with 1/4‑28 UNF) and with certified versions (e.g., 330500-00-02 with ATEX), to guide proper selection for non‑hazardous applications requiring flexibility in mounting.

Functional Description and “Bare” Mounting Philosophy

The 330500-00-00 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 330500-00-00 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 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.

This “bare” configuration is particularly advantageous for:

• Custom installations where a specific adapter is required that is not offered as a standard option.

• Retrofit projects where existing mounting hardware already has a 3/8‑24 UNF thread.

• Cost‑sensitive projects where the cost of the adapter can be saved or sourced locally.

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 330500-00-00 with other common configurations: the 330500-01-00 (1/2‑20 UNF adapter, no approvals), the 330500-03-00 (1/4‑28 UNF adapter, no approvals), the 330500-00-02 (no adapter, ATEX approved), and the 330500-01-04 (1/2‑20 UNF adapter, multiple approvals). This comparison highlights the unique value of the -00-00 for flexible, non‑hazardous applications.

Selection Guide – Key Differences

The 330500-00-00 is the most flexible and economical configuration in the 330500 series. Choose this variant when:

• You need a velocity sensor for a non‑hazardous (safe) area.

• 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.

• You do not require explosion‑proof or intrinsic safety certifications.

If you need a specific adapter (e.g., 1/2‑20 UNF for quick‑connect mounts), choose the corresponding -01, -02, -03, etc. If you require hazardous area approvals, choose the -02 (ATEX) or -04 (multiple approvals) options. For NPT mounting, the 330525 or the 21128 housing assembly is recommended.

Hardware Characteristics – Specific to 330500-00-00

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 330500-00-00 is compatible with the same two‑conductor shielded cables as all 330500 variants. 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).

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)

Application Guidelines – When to Use 330500-00-00

The 330500-00-00 is recommended for machinery monitoring applications where:

• The sensor will be installed in a non‑hazardous (safe) area.

• Direct velocity output is required for compatibility with monitoring systems that accept velocity signals (e.g., many Bently Nevada monitors).

• The mounting solution requires flexibility – you may have a pre‑existing 3/8‑24 UNF threaded hole, or you plan to use a custom adapter not offered as a standard option.

• Cost savings are a priority – omitting the factory‑supplied adapter reduces the purchase price.

• The installation does not require explosion‑proof or intrinsic safety certifications.

Typical machinery applications include:

• Gas turbines and steam turbines (casing vibration)

• Centrifugal and reciprocating compressors

• Industrial fans, blowers, and pumps

• Gearboxes and high‑speed rotating equipment

• Generators and motors

When to choose a different configuration:

• If you need a specific adapter (e.g., 1/2‑20 UNF for quick‑connect mounts), choose 330500-01-00.

• If you require hazardous area approvals (ATEX, CSA), choose 330500-00-02 or 330500-01-04.

• If you need NPT mounting, consider the 330525 or the 21128 housing assembly.

Installation Best Practices for 330500-00-00

1. Surface Preparation – Clean the mounting surface to remove paint, rust, or debris. Achieve a surface finish of 32 µin rms or better (e.g., by lapping). Ensure the threaded hole matches the 3/8‑24 UNF‑2B thread and is perpendicular to the measurement axis.

2. Sensor Mounting – If using the body thread directly, apply a thin layer of anti‑seize compound (if required) and hand‑tighten the sensor into the hole. Then torque 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 of the sensor body. If using a custom adapter, install the adapter first, then mount the sensor.

3. Cable Connection – Align the 2‑pin connector (Pin A and Pin B) and tighten the coupling nut securely. For long cable runs, use the recommended 18 AWG cable (02173006 or 125065) to minimise voltage drop and signal loss. Route cables away from high‑voltage lines and avoid sharp bends.

4. Grounding – Because the case is isolated, the sensor does not require a separate ground. However, the cable shield should be connected to the monitoring system’s common reference at the power supply end to minimize electrical noise. Do not ground the shield at both ends to avoid ground loops.

5. Environmental Protection – For outdoor installations, use splash boots (available separately) and ensure all cable connections are sealed. The sensor itself is IP68, but the cable termination may require additional protection.

Comparison with Other No‑Adapter Options – Why Choose 330500-00-00?

• vs. 330500-01-00 (1/2‑20 UNF) – The -01 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 saves cost and provides the flexibility to use any adapter you choose.

• vs. 330500-03-00 (1/4‑28 UNF) – The -03 includes a 1/4‑28 UNF adapter, a common thread for many accelerometer bases. If your mounting hardware requires 1/4‑28, the -03 is a direct fit. If not, the -00 allows you to use a different thread.

• vs. 330500-00-02 (ATEX) – The -02 adds ATEX certification for hazardous areas. If your plant is non‑hazardous, the -00 is more cost‑effective and does not require certified barriers.

• vs. 330500-01-04 (multiple approvals) – The -04 includes 1/2‑20 UNF adapter and multiple certifications. The -00 is the economical choice for safe, flexible installations.

Ordering Information

When ordering the 330500-00-00, 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)

• -00 – Agency Approval: None

Compatible Cables and Accessories

Note: The 330500-00-00 does not include a cable or adapter; order separately.

Certifications and Compliance

Because the -00 option has no hazardous area approvals, it is certified for general industrial use only. It complies with:

• FCC Part 15 – Radio frequency interference limits.

• EMC Directive 2014/30/EU – Electromagnetic compatibility.

• RoHS Directive 2011/65/EU – Restriction of hazardous substances.

• China RoHS – EFUP of 15 years (SJ/T 11364-2024).

• ABS – (Marine Vessels, Offshore Units) – the sensor itself is approved for maritime use even without explosion protection.

It is NOT rated for ATEX, IECEx, or CSA hazardous locations. If your installation requires intrinsic safety, you must order the -02 or -04 option.

Warranty and Support

The Bently Nevada 330500-00-00 is covered under the standard manufacturer’s warranty (refer to Bently Nevada Terms and Conditions). For technical support, application assistance, or custom configurations (e.g., custom adapters), contact your local Bently Nevada sales representative or access the Bently Nevada Media Library at bntechsupport.com.