Configured for casing vibration monitoring, the Bently Nevada 991-06-50-02-00 (991-06-50-02-00 Vibration Transmitter) provides direct electrical execution for signal conditioning and 4-20 mA loop transmission.

Model Configuration Matrix

• 991: Base Model (Vibration Transmitter)
• 06: System length configuration
• 50: 5.0 meters system length
• 02: Bulkhead screw mounting option
• 00: No additional requirements

Hardware Specifications

Mechanical Monitoring and Signal Integrity

The 991 transmitter employs precise eddy-current probe scaling to convert sensor proximity data into a linear 4-20 mA output. Installation requires gap voltage validation (targeted at -10 VDC) to ensure the transducer system operates within the linear range of the rotor dynamics envelope. The device architecture incorporates cross-talk suppression to maintain signal fidelity in environments where multiple transmitters are installed in close proximity. Non-interacting adjustments allow for field calibration of the zero and span points, ensuring accurate representation of machinery vibration across the specified measurement band.

Ordering Info

• 1 x 991-06-50-02-00 Vibration Transmitter
• 1 x Bulkhead mounting screw hardware set

Installation Guidelines

• Power Supply: Connect a DC source within the 12-35 VDC range to the transmitter terminals; ensure proper polarity to prevent damage to internal circuitry.
• Mounting: Secure the transmitter using the provided bulkhead screws in an environment free from excessive moisture and corrosive vapors.
• Grounding: Terminate the signal cable shield to a common system ground to mitigate EMI and noise accumulation on the 4-20 mA loop.
• Loop Integrity: Ensure total loop resistance, including cable, does not exceed 1,000 Ohm at 35 VDC to maintain loop current control.

Frequently Asked Questions

• What is the primary function of the 23 mA current limiting?

  This safety feature limits current during fault conditions or loop shorts, protecting the internal transmitter components and downstream instrumentation from damage.

• Can this transmitter be calibrated without removing it from service?

  The zero and span adjustments are external and non-interacting, allowing for calibration while the transmitter is powered and loop-connected.

• Does the system length (5.0 m) affect the signal frequency response?

  Yes, the total system length includes the probe, extension cable, and transmitter; the frequency response is factory-tuned for this specific configuration.

• What happens if the input voltage drops below 12 VDC?

  Operation below the minimum 12 VDC threshold may cause output signal instability or complete loss of transmitter function.

• How is the transmitter output impacted by load resistance?

  Exceeding the maximum 1,000 Ohm load resistance at 35 VDC will result in a drop in loop current, preventing the transmitter from reaching the full span output.

• Is this transmitter compatible with legacy 3300 series probes?

  Compatibility is generally maintained within the Bently Nevada 990/991 ecosystem; verify probe series matching via technical manuals for specific impedance curves.

• Are shielding requirements strictly dependent on the cable length?

  Shielding is required for all installation lengths to ensure RFI/EMI immunity, specifically when operating near high-frequency industrial radio equipment.

• Why is bulkhead mounting specified for this model?

  Bulkhead mounting provides structural stability and grounding continuity, reducing mechanical vibration stress on the transmitter housing.