Configured for radial vibration and axial position measurements in machinery protection applications, the Bently Nevada 21504-32-56-10-02 (21504 Proximity Probe) provides direct physical/electrical execution.

Option Code Configuration Matrix

The physical structure, thread dimensions, and cable options for this 7200 Series standard mount probe are designated by the following options:

• 21504: Base model number for the 7200 Series 8 mm Standard Mount Proximity Probe (3/8-24 UNF thread).

• -32: Configures an unthreaded case length of 3.2 in.

• -56: Specifies an overall case length of 5.6 in.

• -10: Selects a 1.0 m (39 in) integrated probe cable length.

• -02: Features an integrated miniature male coaxial connector.

Hardware Specifications

Eddy-Current Probe Scaling and Rotor Dynamics Integration

The 21504-32-56-10-02 probe relies on eddy-current probe scaling to convert physical gap changes into high-fidelity electrical signals. When excited by a 7200 Series Proximitor Sensor, the probe tip generates an RF magnetic field. Target movements on the rotating shaft interrupt this field, causing proportional voltage variations that monitor complex rotor dynamics, including radial vibration and axial thrust displacement.

To prevent signal degradation and cross-talk, the probe requires careful gap voltage validation. Physical adjustment of the 3/8-24 mounting thread is required until the static gap voltage reads a nominal -10 VDC at the Proximitor. This positions the target at the exact center of the 2.0 mm (80 mils) linear operating range, maintaining a stable 200 mV/mil scale factor and suppressing cross-talk on closely spaced sensor arrays.

Ordering Info

• 1 x Bently Nevada 21504-32-56-10-02 Proximity Probe

• 2 x Integral hex jam nuts

Field Installation Guidelines

• Thread Depth and Locknut Tension

  Install the probe into the mounting brackets, taking care to maintain the 3.2 in unthreaded portion clear of obstructions. Torque the dual jam nuts to secure the probe body against extreme machine vibration.

• Coaxial Connector Isolation

  The miniature male coaxial connector must remain completely isolated from the machine housing. Always install a flexible connector insulator sleeve over the male-to-female junction to prevent ground loops.

• Cable Routing and Bending Limits

  Route the 1.0 m integrated cable using a minimum bending radius of 25.4 mm (1.0 in). Use protective conduit where possible, and avoid sharp bends or tight cable ties that deform the coaxial structure.

Frequently Asked Questions

• What target gap voltage is required for standard linear calibration?

  The probe must be adjusted in its mounting bracket until the Proximitor loop output measures a target of -10 VDC.

• Is this 7200 series probe compatible with a 3300 series Proximitor?

  No, the internal electrical characteristics are specifically tuned for 7200 series Proximitor sensors and extension cables.

• Can this probe operate in environments containing corrosive process gases?

  Yes, the PPS tip material resists typical industrial lubricants and synthetic fluids, but the connector must remain clean and dry.

• How does targeting a non-steel shaft affect the calibration?

  Standard calibration assumes AISI 4140 steel. Target materials like stainless steel or aluminum will significantly alter the scaling factor.

• What is the consequence of exceeding the minimum cable bending radius?

  Bending the coaxial cable below 25.4 mm deforms the internal insulation, introducing impedance mismatch and electrical noise.

• Does this model support hot-swapping while the protection system is live?

  Yes, but disconnecting the probe cable interrupts the loop, causing a "Not OK" fault condition in the monitor channel.

• How is cross-talk suppressed between adjacent proximity probes?

  Ensure a minimum radial distance of 40 mm is maintained between the tips of adjacent 8 mm probes.

• What happens if the probe tip contacts the rotating target shaft?

  The physical impact will destroy the internal coil and tip structure, leading to immediate loop failure and sensor fault alarms.