Configured for routing analog AC velocity signals from piezo-velocity sensors to machinery protection monitors in Turbomachinery Instrument (TSI) monitoring loops, the Bently Nevada 89477-27 (89477 Interconnect Cable) provides direct physical/electrical execution. It connects 330500 and 330525 Velomitor Piezo-Velocity sensors or 21128 housings directly to the input terminals of TSI monitoring racks.

Part Number Code Structure

The ordering configuration for the 89477-27 interconnect cable specifies the structural and physical length limits of the assembly:

• 89477: Base model identification for the 2-conductor shielded twisted-pair cable with a right-angle plug connector.
• -27: Specifies the nominal cable length option, designating a 27-foot (approx. 8.2 meters) assembly.

Hardware Specifications

Rotor Dynamics Signal Integrity & Impedance Stabilization

In high-vibration rotating machinery environments, maintaining signal integrity over the interconnect link is necessary for precise rotor dynamics tracking. The 89477-27 cable features a balanced 95 ohm characteristic impedance paired with low capacitance (less than or equal to 45 pF/m) to prevent signal attenuation and phase shifts of high-frequency casing vibration components.

The stranded copper conductors and braided shield provide high immunity against electromagnetic interference (EMI) and signal cross-talk suppression from adjacent high-voltage lines. This mechanical and electrical isolation guarantees that the dynamic AC waveform remains undistorted as it travels from the transducer to the TSI backplane.

Included Hardware Checklist

• 1 x Bently Nevada 89477-27 Interconnect Cable (27-foot overall length)
• 1 x Pre-installed right-angle 2-socket female plug (sensor termination)
• 2 x Terminal lugs (pre-crimped at monitor termination end)

Field Installation & Shield Grounding Guidelines

• Minimum Bend Radius Configuration

  During installation, ensure the cable routing trajectory maintains a physical bend radius of at least 75 mm. Bending the cable beyond this limit can fracture the internal shielding layer and strain the 18 AWG copper conductors.

• Shield Grounding Method

  The outer shield drain wire must be terminated at the machinery protection monitor chassis ground only. The shield must be left floating and insulated at the sensor/transducer housing end to prevent the formation of ground loops.

• Installation with 21128 Housing

  When feeding the cable into a 21128 Velocity Transducer Housing, verify the right-angle plug fits securely into the mating sensor socket without exerting lateral mechanical tension on the connection boot.

Frequently Asked Questions

• Can this cable be used with eddy-current proximity probes?

  No. Proximity probes require matched impedance coaxial cables. The 89477-27 is a twisted-pair shielded cable designed for piezo-velocity sensors.

• What is the minimum allowable bend radius for routing?

  The cable must be routed with a bend radius of 75 mm or greater to prevent damage to the inner conductors and braided shielding.

• How should the shield of this interconnect cable be terminated?

  The shield should be grounded at the monitor end only. Leave it floating at the transducer housing end to avoid creating ground loops.

• What is the maximum operating temperature for this cable?

  The cable has an operating temperature rating of -40 deg C to +100 deg C, making it suitable for hot industrial environments.

• Does this cable support hot-swapping at the sensor end?

  Yes, but disconnecting the cable while the channel is active will cause the connected monitor to trip into a "NOT OK" or sensor fault status.

• What is the cross-sectional area of the conductors?

  The cable uses two 18 AWG conductors, with each conductor having a cross-sectional area of 0.82 mm2 of stranded copper.

• Can this cable be routed through liquid conduit?

  The cable can be run in conduit, but it must not be permanently submerged in liquids as it is not rated for continuous submersion.

• What is the DC resistance limit of this cable?

  The DC resistance is specified at less than or equal to 22 ohms per 1000 feet, which ensures minimal signal loss over maximum lengths.