The Bently Nevada 18745-04, also cataloged as the 18745 Proximitor Sensor, operates as a dedicated hardware component for signal conditioning within 7200 Series machinery protection systems. Configured for use with a combined probe and extension cable system, the device processes high-frequency carrier signals to detect inductive impedance changes. It provides a linear voltage output proportional to the gap between the probe tip and the monitored target, enabling continuous observation of shaft displacement and vibration in rotating equipment.

Hardware Specifications

Eddy-Current Probe Scaling and Rotor Dynamics

The 7200 Series Proximitor relies on calibrated eddy-current probe scaling to convert target proximity into a usable DC signal. Successful integration requires gap voltage validation to -10 VDC targets at the Proximitor output during cold-start commissioning. This calibration ensures the probe is centered within its linear range, which is mandatory for accurate rotor dynamics analysis. Signal integrity is maintained through effective cross-talk suppression by keeping sensor cabling routed in dedicated, shielded pathways to avoid electromagnetic interference from adjacent high-speed signal lines or power distribution conduits.

Ordering Info

• 1 18745-04 Proximitor Sensor

• 1 Technical configuration leaflet

Field Installation Guidelines

• Mounting

• Secure the Proximitor unit in a vibration-isolated, dry enclosure using the integrated mounting holes.

• Maintain clear access to the terminal blocks for monitoring output voltages.

• Wiring

• Ensure the -24 VDC power supply is stabilized and properly referenced to the system common.

• Connect the coaxial probe/extension cable assembly to the BNC or screw-terminal input, ensuring the shield is continuous and well-terminated to prevent noise injection.

Frequently Asked Questions

• Is the 18745-04 compatible with 3300 series probes?

  No, the 7200 series Proximitor is electrically tuned for 7200 series probes. Mixing with 3300 or 3500 series hardware will produce erroneous output data.

• Can the sensor be powered by a 12 VDC source?

  The device requires a nominal -24 VDC supply. Operating outside of the specified voltage range will cause signal clipping and non-linear performance.

• Is the 9 meter system length flexible?

  The length is fixed by the system tuning. Modifying the probe or extension cable length will shift the system resonant frequency and invalidate the sensitivity.

• What does the "2-wire" designation mean?

  It refers to the integrated power and signal loop architecture where the output signal is superimposed on the DC power supply lines.

• How is the system grounded?

  The system should be grounded at a single common point to prevent ground loops. Ensure the Proximitor case is bonded to the chassis ground if required.

• Does this device support digital signal output?

  No, the 7200 series Proximitor is a purely analog device providing an instantaneous voltage output proportional to the gap.

• What is the response to an open circuit?

  An open circuit in the probe or extension cable will cause the output to swing to the negative supply rail, indicating a "Not OK" fault condition.

• Are the connectors hot-swappable?

  While the circuitry is robust, disconnecting the probe while the system is powered will cause a transient signal spike, which may trigger protection system alarms.