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VM-21 Vibration Monitor



VM-21 Vibration Monitor Operation


The VM21 measures vibration or voltage signal from two channels. The signal source can be an ICP type accelerometer for vibration analysis or any sensor that produces a voltage signal. The vibration levels are measured and updated every second.

The VM-21 allows programming machine condition zones (ISO 10816) by setting vibration thresholds levels. The measured vibration levels are compared to the thresholds and depending on the machine condition the levels are presented in green, yellow or red. Besides, several diagnostic symptoms are presented.


The following displays and indications are used in the VM-21 for each channel

  • Numeric display showing the current vibration value. The units and scale are user-programmable (acceleration, velocity, displacement, etc.)
  • Color bar graph. 5 different color options
    • blinking green - level below low alarm
    • green - level below acceptable threshold
    • yellow - level above acceptable, below alert threshold
    • red - level above alert, but below danger
    • blinking red - level exceeds danger alarm

    Note, the bar height represents the full scale of the current condition zone so you can estimate with high precision if the current level is close or far from the condition zone boundary.

    All thresholds levels are user programmable.

  • Diagnostic indicators
    • Increase of vibration level - switches on when the trend of vibration increase becomes stationary. It is important to have such an indication even if the increase continues within one condition zone.
    • Jump of vibration level - rapid changes in vibration pattern. Once a Jump is registered, the indication will be on until operator resets it manually.
    • HF vibration - High frequency vibration level. It means that high frequency vibration exceeded the threshold set up by the user. It is a typical symptom for bearing or lubrication problems. HF vibration levels are measured simultaneously with the indicated vibration levels.
    • Error - system mulfunction. Typically accelerometers or cables open or short circuit. Errors in digital circuits are indicated on the numerical display.


The following actions can happen on the VM-21:

  • Each chanel has 4-20 mA output corresponding to the measured vibration level
  • Each channel has two relay lines that can be individually programmed to switch on when any event happens in the corresponding channel
    • any of the alarm thresholds exceeded
    • any of the diagnostic indicators switch on


The VM-21 can operate as a standalone system or can be integrated in the computer network of the enterprise. All the information available in the VM-21 can be transfered via RS-485 industry standard interface via MODBUS RTU protocol to the host computer. The OPC Server distributes the information along the computer network of the enterprise.

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