Analytical Instrumentation

GAP voltage of Bently Nevada Vibration Probe

GAP voltage of Bently Nevada Vibration Probe 1
  • Bently Nevada is one of the popular manufacturers of vibration and condition monitoring equipment. 
  • Generally, the term “Gap Voltage” is not used in Bently Nevada vibration probe systems, 
  • However, in practice, we are referring to the “Probe Gap” or “Air Gap.”
  • Typically, the term Probe Gap or Air Gap defines the actual length between the probe’s tip of proximity and the target surface such as the rotating shaft which needs to be monitored.
  • This Probe Gap or Air Gap is essential for vibration measurements with high accuracy.
  • This Probe Gap or Air Gap affects the sensitivity of the probe and its ability to ascertain minimum changes in the position of the target.
  • This voltage is employed to observe the vibration and position of the machine.
  • The actual value of the Gap voltage varies for the specific make and model of the probe and its calibration procedure.
  • The specific gap voltage of a Bently Nevada vibration probe can be determined by referring to the documentation provided by the manufacturer.
  • Bently Nevada issues detailed specifications and calibration procedures for their particular probe model in their user manuals and technical documentation.

What is GAP voltage?

GAP voltage of Bently Nevada Vibration Probe 2
  • GAP voltage is defined as the voltage between the gap of the tip of an electrode or probe and the work-piece shaft’s surface. 
  • The gap voltage is the voltage developed by the proximity probe when it detects minimum changes in the position of the target.
  • GAP voltage is the quiescent voltage that is required to be adjusted between the range limits of proximities output voltage.
  • Generally, the GAP voltage of the Bently Nevada Vibration Probe is set to -10V DC. Because the proximity permits the vibration probe to operate in its region of linearity from -2VDC to -18VDC.
  • The Voltage difference is 8 volts in the case of 2VDC to 10VDC or 10 VDC      to 18VDC.
  • The probe determines the vibration equally at both sides, meaning      when the shaft is moving away from the probe or when the shaft is moving towards the probe.

Does the Probe detect vibration if adjusted for -9 volts?

  • Yes, the probe easily detects the vibration if it is adjusted for -9 volts.
  • The vibration margin on one side will be 7 volts, and on the other side the vibration margin is of 11 volts
  • At a margin of 11 volts, the probe detects excellent vibration.
  • But, at a margin of 7 volts on the other side there are some limitations where the probe may not detect vibration.
  • The standard output of a vibration probe is typically an AC voltage signal, and the amplitude of this signal varies with the vibration level of the monitored machinery. 
  • The signal is then processed and analyzed by monitoring and control systems to assess the condition of the machinery and detect any abnormalities or faults.
  • If you have a specific application or situation where you are dealing with a voltage level of -9 volts, it would be important to provide more context and details for a more accurate and tailored response. 
  • However, in the context of a typical vibration probe, it does not adjust its output voltage to a specific DC level like -9 volts for vibration detection.     

Why do we use Negative Voltage in Vibration Measurement? How does an eddy-current proximity probe work?

GAP voltage of Bently Nevada Vibration Probe 3
  • Eddy-current proximity probes work on the principle of electromagnetic induction. They consist of a coil of wire that is excited with an alternating current (AC) to produce a magnetic field.
  • An eddy-current probe operates by conveying an alternating current through a coil of wire and by determining the impedance of the coil. 
  • This impedance varies when an eddy-current probe is brought close to electrically conductive material.
  • When the probe’s coil is energized with AC voltage, it induces eddy currents in the metal target object. The strength and phase of these eddy currents are influenced by the distance between the probe and the target.
  • The change in impedance is proportional to the physical gap between the coil and the conductive target. 
  • The sensing unit in turn transforms this change in impedance to a voltage signal to provide an electrical output.
  • When the target object vibrates or changes its position, the distance between the probe and the target varies. 
  • This results in changes in the eddy currents induced in the metal, which, in turn, affect the amplitude and phase of the AC voltage output from the probe.
  • The probe generates an AC voltage signal that represents the changes in proximity between the probe and the target. 
  • The signal’s phase and amplitude change with vibration or positional changes of the target object. By analyzing these changes, the vibration and positional information can be extracted.     

 What is the gap voltage for the Bently Nevada 3300?

  • The Gap Voltage for the Bently Nevada 3300 must lie between -9 Volts  to -11 Volts
  • Since Vibration probes are installed at a distance of the shaft equal to ca

What is the length of a vibration probe?

Based on the application & probe tip the length of a vibration probe varies between 5 mm, 8 mm, and 11 mm. 

What is the setting of the vibration probe?

  • The standard Field setting of the vibration probe recommended by the company must be between -9.5 VDC and -10 VDC.
  • The vibration probe needs to be set by removing the vibration probe cover and probe lock nut with two spanners if the output voltage is not -10 VDC.

What is the SI unit of vibration?

SI unit of vibration watts per square meter (W/m2)

What is 1 vibration equal to?

1hertz. Frequency of 1 Hz implies to 1 complete vibration per second. This means, 60 complete vibrations in 60 second, or, in 1 minute.

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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