IMI Sensors’ 682B05 Bearing Fault Detector (BFD)

Monitor and Detect Bearing Faults to Avert Catastrophic Failure

Bearing fault detector 982B05 IMI Sensors FTR

Model 682B05 Bearing Fault Detector (BFD) is an advanced vibration signal conditioner designed to provide the earliest warning of imminent machinery failure. The unit works with a 100mV/g ICP® accelerometer and serves to deliver two, 4 to 20mA output signals that are proportional to the measured vibration levels of operating rotating machinery. In order to enable detection of a wide variety of machinery faults, the 4 to 20mA signals are conditioned to characterize two, unique vibration measurements; one containing high frequency peak data and the other containing low frequency rms data. These 4 to 20mA signals may be monitored, alongside other plant process variables, using familiar PLC, DCS, SCADA, alarm and control systems. An additional analogue voltage output signal is provided for spectral analysis of the monitored vibration for fault diagnostic purposes.

The unit employs a patented signal conditioning technique that provides the unique ability to detect bearing and gear problems at their earliest stages, thus permitting ample maintenance planning to avert a catastrophic failure. The simplified 4 to 20mA signal monitoring approach represents a cost effective alternative to complex vibration monitoring instrumentation and associated training.


  • Provides Early Warning of Bearing and Gear Faults
  • Detects Impacting Associated with Spalling, Cracking, and Lubrication Problems
  • Outputs 4 to 20 mA Signals for Peak Acceleration and Overall Vibration
  • Operates with PLC, DCS, SCADA, Alarm and Control Systems
  • Offers Analog Output Signal for Spectral Analysis and Diagnostics
  • Conducts Continuous Vibration Monitoring — 24/7
  • Accepts Input from ICP® Accelerometers
  • Patented Technology
  • Easy to Install

Machinery vibration monitoring has long been recognised as an effective practice for detecting mechanical problems that ultimately cause machinery failure and downtime. Unfortunately, many instrumentation systems that are intended to assist the maintenance engineer with vibration analysis are complex — and require considerable training and experience in order to interpret measurement data. Too often, companies may encounter the loss of an experienced maintenance engineer due to downsizing or attrition — leaving critical machinery to run without being monitored and expensive analysis equipment to lay idle.

In recent years, industrial accelerometers have advanced in performance capability and declined in price, making their deployment for machinery vibration monitoring a more attractive undertaking. Additionally, vibration transmitters, with 4 to 20mA output signals, have permitted vibration monitoring to occur with plant process control equipment, such as PLCs, alarm, and control systems, thus reducing the expense, complexity, and risk of talent loss associated with sophisticated vibration analysis. Although not as precise as analogue vibration signal analysis, overall vibration level monitoring with IMI Sensors’ 4 to 20mA transmitters is effective for providing early warning of machinery trouble.

Why use IMI Sensors’ 4 to 20 mA vibration transmitters?
Industrial plants rely on monitoring, control, and alarm systems for interrogating many process variables, such as flow, level, temperature, pH, and pressure. Although a variety of communication protocols are in use, 4 to 20mA transmitters are the common source for the measurement data of interest. When machinery vibration is considered within the list of variables in need of evaluation, the existing infrastructure of process monitoring and control instrumentation becomes an attractive choice for data examination. To accommodate this, a variety of 4 to 20mA vibration transmitters have been introduced. These transmitters may be incorporated within the vibration sensor — or separately housed in a signal conditioning package. Depending on the amplitude and frequency of the vibration to be monitored, the vibration data can be most successfully characterised in acceleration, velocity or displacement units of measure — so the output format of a vibration transmitter should be selected accordingly for best results.

What makes IMI Sensors’ BFD different?
The IMI Sensors Model 682B05 BFD is a signal conditioner characterised as a separately housed vibration transmitter. The unit mounts to DIN rail and accepts an analogue vibration signal as generated from a 100mV/g ICP® accelerometer. Three different vibration output signals are provided by the BFD:

  • The raw, analogue voltage signal generated by the accelerometer
  • A linear, 4 to 20mA signal proportional to overall rms or peak vibration and expressed as either acceleration or velocity
  • A linearly scaled, 4 to 20mA signal proportional to true peak acceleration


It is the measurement of true peak signal that makes the BFD unique, powerful, and patented.

The benefit of this unique measurement is its ability to detect short duration pulses or impacts that are indicative of bearing and gear problems. Because they are short in duration they have little influence on a typical overall vibration signal. This unique capability enables the BFD to provide the earliest warning of bearing and gear problems through an ordinary 4 to 20mA signal. This permits the user to initiate the diagnostic and maintenance process sooner in order to avoid a catastrophic and costly machinery failure.

What are the signal conditioning techniques utilised by the BFD?
Output signal type (1) is the raw, analogue voltage signal generated by the accelerometer. Since the BFD is scaled to operate with a 100 mV/g ICP® accelerometer, this output signal will be approximately 100mV/. More precision can be achieved by using the sensitivity supplied with the accelerometer at the measurement device. This analogue signal is provided on the BNC jack output connector and is useful for spectral (FFT) analysis of the vibration signal for fault diagnostics. Output signal type (2)is a 4 to 20 mA signal proportional to overall, rms or peak vibration. Internal selection switches allow a choice of acceleration or velocity measurements, peak or rms values, and a variety of fixed measurement ranges. The signal generated by the accelerometer is initially processed through a 1 kHz low pass filter. Then when set for velocity, the BFD passes this filtered signal through an integration circuit. When set for acceleration, the filtered signal bypasses the integration circuit. At the next stage, the signal passes through a true RMS conversion circuit. Finally, a gain stage provides scaling of the velocity or acceleration signals to one of a variety of fixed full-scale measurement ranges. Another gain adjustment converts the rms measurement value to a calculated peak (1.414 x rms) measurement value, if desired. This overall vibration signal is a useful indicator of faults that occur at machine running speeds, such as imbalance, misalignment, and looseness.

Output signal type (3) is a linearly scaled, 4 to 20mA signal proportional to true peak acceleration. The signal generated by the accelerometer is passed through a high pass filter, selectable at either 1 kHz or 5 kHz, depending upon machine running speed, and then rectified. The peak acceleration value that occurs within a 7-second window is then captured by a high speed sample and hold circuit and converted to a 4 to 20mA output signal. A new value is captured during the next window and a refreshed peak output value is generated every 7 seconds. This peak acceleration signal is a useful indicator of impacting or high frequency energy bursts — characteristic of the early stages of bearing and gear faults, such as spalling, friction, fatigue, cracking, contamination, and lubrication problems.

For more information on the IMI Sensors Bearing Fault Detectors, contact John Morris Industrial today:

Phone: +61 2 9496 4200




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