3300/65 - Dual Probe Monitor

3300/65 - Dual Probe Monitor 3300/65 - Dual Probe Monitor

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Part Number: 3300/65
Manufacturer: Bently Nevada
Series: 3300
Product type: Dual Probe Monitor
Full-Scale Range: 0 to 15 mils
Relative Transducer Input: 3300 or 7200 Proximitor
Agency Approval: Not Required
Intrinsic Safety Barrier: None
Seismic Transducer / Alarm Relay: Velomitor, No Relay
Trip Multiply: None
Availability: In Stock
Country of Manufacture: United States (USA)

Functional Description

3300/65 is a dual probe monitor designed and developed by Bently Nevada. Dual Probe Monitor combines the shaft relative displacement signal from a Bently Nevada proximity transducer and casing vibration from a velocity transducer, both of which are installed in the same axis on the machine, into a single measurement of shaft absolute vibration. Dual Probe Monitors are intended for use in machines with fluid film bearings, such as large steam and gas turbines, where shaft vibration is transmitted to the case. The Dual Probe Monitor provides four distinct measurements:

  • Shaft relative vibration - A measurement of shaft vibration relative to the bearing housing using a proximity probe.
  • Bearing housing vibration - A seismic measurement of the vibration of the bearing housing in relation to free space.
  • Shaft absolute vibration - A vector sum of shaft relative and bearing housing vibration.
  • A proximity probe dc gap measurement of the shaft's average radial position relative to the bearing clearance.


  • The Dual Probe Monitor excels at harmonizing the data obtained from two sources: the shaft relative displacement signal from a Bently Nevada proximity transducer and the casing vibration signal from a velocity transducer. Both sensors are thoughtfully positioned along the same axis on the machine. By combining these signals, the monitor provides a comprehensive measurement of shaft absolute vibration, allowing for a more complete assessment of machine dynamics.
  • Enhanced Precision and Analysis: This innovative approach to monitoring brings enhanced precision and analytical capabilities to the table. The amalgamation of shaft relative displacement and casing vibration signals facilitates a more nuanced understanding of machine behavior. This comprehensive view can unveil subtle irregularities and deviations that might not be evident when analyzing each signal individually.
  • Relevance to Fluid Film Bearings: Dual Probe Monitor finds particular relevance in machines equipped with fluid film bearings, such as steam and gas turbines. In these systems, where the vibration of the shaft is transmitted to the casing, the dual probe approach proves valuable. It offers a holistic perspective on the mechanical interactions within these intricate systems, aiding in diagnostics and decision-making.
  • Advancing Monitoring Technology: By seamlessly integrating distinct signals into a single measurement, the product showcases the evolution of monitoring technology. This innovation empowers industries to make informed decisions based on a more complete understanding of their machinery's performance. It aids in anticipating issues, enhancing operational efficiency, and ensuring smooth processes.


  • Signal Acceptance and Integration: The monitor possesses the capability to accept two distinct signals. One signal originates from a proximity transducer, while the other comes from a 600 cycles per minute (cpm) 2-wire velocity transducer. These signals are seamlessly integrated to provide a comprehensive view of the machine's behavior.
  • Relative Transducer Impedance: For the relative transducer input, the monitor accommodates a 10 k ohm impedance. This specification ensures compatibility and efficient signal processing from the relative transducer.
  • Seismic Transducer Impedance (2-Wire): In the case of seismic transducer inputs, the monitor supports a 10 k ohm impedance for 2-wire transducers. This impedance parameter ensures effective integration and accurate data acquisition from seismic transducers.
  • Proximity Probe Sensitivity (Jumper-Selectable): The proximity probe input offers jumper-selectable sensitivity options. The available sensitivities are 200 mV/mil (7.87 V/mm) and 100 mV/mil (3.94 V/mm). This customization enables users to align the monitor with specific operational requirements.
  • Seismoprobe Sensitivity: For seismoprobe inputs, the monitor accommodates a sensitivity of 500 mV/(in/s) (19.69 mV/(mm/s)). This parameter indicates the responsiveness of the monitor to seismic vibrations, aiding in accurate data acquisition.
  • Velomitor Sensitivity: When interfacing with Velomitor transducers, the monitor accepts a sensitivity of 100 mV/(in/s) (3.94 mV/(mm/s)). This sensitivity parameter ensures precise velocity data acquisition from the transducer.
  • Power Consumption Efficiency: The monitor's power consumption is designed for efficiency, with a nominal consumption of 1.5 watts. This attribute indicates that the monitor is energy-conscious while delivering reliable performance.

Frequency response

  • Corners with nominal -3dB Userprogrammable for proximity transducer at 4 to 4,000 Hz (240 to 240,000 cpm) or 1 to 600 Hz (60 to 36,000 cpm)
  • Seismic at 4 to 4,000 Hz (240 to 240,000 cpm); Absolute at 10 to 4000 Hz (600 to 240,000 cpm). (or 36,000 cpm if the 1-600 Hz relative option is chosen)
  • The 1 to 600 Hz (60 to 36,000 cpm) frequency range is not recommended for machine applications that require rapid startup and coastdown rates and acceleration/deceleration rates greater than 1,000 rpm per second. The monitor circuitry will retain vibration transients normally experienced during fast startup because of the extended low frequency range to 60 cpm.

Alarm Setpoints

  • Alarms (Alert, Danger, and Gap) are digitally adjustable from 0 to 100% of full-scale and can be set to a desired level within LCD resolution (1.66% of full-scale).
  • Alarms are repeatable to within 0.4% of full-scale once set.



  • Liquid Crystal Display with nonmultiplexing vertical bargraph (LCD). Each channel has 63 individual LCD segments.
  • On a third, center scale, the probe gap is indicated. The LCD also shows error codes and the ADJUST mode.


  • Within ±1.6% of monitor fullscale.


  • 83 mm (3.2 in), vertical dimension.

LED Indicators

  • One constant ON green LED per channel indicates that the monitor, transducers, and field wiring are in good working order.
  • Constant OFF indicates a NOT OK condition or that the channel has been bypassed (red Bypass LED will be ON). OK LED flashing at 1 Hz indicates transducer has been NOT OK, but is now OK.
  • OK An LED flashing at 5 Hz indicates that an error code (or codes) has been stored in memory. There is one OK LED for the relative transducer and one for the seismic transducer.


  • Two red LEDs per channel indicate the status of the alarm (independent Alert and Danger LEDs for each channel).
  • First Out is indicated by a flashing alarm LED (independent for Alert and Danger alarms).


  • The status of the Danger Bypass and Rack/Channel Bypass functions is indicated by two red LEDs.

Environmental Limits

  • Operating Temperature: 0 to +65 degrees Celsius
  • Storage Temperature: -40 to +85 degrees Celsius
  • Relative Humidity: To 95%, noncondensing.

Physical Characteristics

  • Rack Space Requirements:The first and second rack slots are designated for Power Supply and System Monitor, respectively.
  • Monitor can be installed in any available rack position.
  • Weight: 1 kg

WOC is happy to assist you with any of your GE requirements. Please contact us by phone or email for pricing and availability on any parts and repairs.


What is 3300/65?
It is a dual probe monitor designed and developed by Bently Nevada.

How does a Dual Probe Monitor work?
The Monitor combines the signals from two types of sensors: a proximity transducer and a velocity transducer. The proximity transducer measures the shaft relative displacement, while the velocity transducer measures the casing vibration. By combining these two signals, the Dual Probe Monitor can calculate the absolute vibration of the shaft.

Why is the component used in machines with fluid film bearings?
In machines with fluid film bearings, such as large steam and gas turbines, shaft vibration is transmitted to the case. This makes it difficult to measure the absolute vibration of the shaft using a single sensor. The Dual Probe Monitor overcomes this challenge by combining the signals from two sensors to calculate the absolute vibration of the shaft.

What are the benefits of using a Dual Probe Monitor?
The main benefit is that it provides an accurate measurement of the absolute vibration of the shaft in machines with fluid film bearings. This allows operators to detect potential problems with the machine before they cause serious damage or downtime. The Dual Probe Monitor is also easy to install and maintain, and can be used in a variety of industrial applications.

How is it installed?
The component is installed in the same axis as the shaft being monitored. The proximity transducer is mounted on the shaft, while the velocity transducer is mounted on the casing. The signals from both sensors are then fed into the Dual Probe Monitor, which calculates the absolute vibration of the shaft.