Air gap measurement

Best practice in air gap measurement using air gap sensors

Air gap measurement using air gap sensors is highly effective for monitoring rotating machines, generators, turbines and electric motors. Full monitoring enables machine condition to be recorded and vital data made available for maintenance purposes.


Special air gap sensors are used to monitor rotating machines for any change in their synchronisation. The distance (air gap) between the rotating rotor and fixed stators is measured in extremely short measuring cycles. High sampling rates of up to 50k samples per second per channel enable reliable detection of even minute changes. To protect the systems, response needs to be extremely fast. Any vibrations and imbalances are detected immediately, the causes quickly diagnosed and any damage to the system quickly determined thereby preventing downtimes.

Many years of experience to achieve effective air gap measurement

  • Highest level of plant safety: Depending on the system, different air gap sensors are used for capacitive or inductive measurement.
  • Flexible sensor data: Different types of plant data such as air gap, temperatures, flow rates and vibrations can be centrally recorded to enable reliable diagnostics to be performed. Measuring can also be triggered by different speeds.
  • High data resolution: For detailed monitoring, the measured data is recorded synchronously by up to 16 sensors at sampling rates of up to 50 KHz per channel.
  • Reliable cause analysis: Individual sensor data requires 100% synchronous recording to enable reliable evaluation of the measured data.
  • Extremely fast response times: Data evaluation takes place parallel to data acquisition using: powerful software channels and FFT spectra; characteristic values; and automated real-time alarms issued to plant control, process control or centralised safety systems.

Developing full systems for specific plant and machinery

  • Measurement and monitoring solution: Full solutions from a single source have established themselves in air gap measurement. Measurement data acquisition and monitoring is combined within a single system and integrated into existing infrastructures using standardised interfaces.
  • Full engineering: Pre-engineering and  application development exploit the experience gained from a large number of projects. Clear dashboards and a diversity of visualisation options are available for monitoring purposes. The service also includes annual calibration.
  • Automated reporting functions: Regular reporting on the condition of plant and machinery with meaningful characteristic values, limit value monitoring and selected process data.
  • Predictive maintenance: Continuous air gap measurement can be extended into predictive maintenance by forecasting a system’s condition and the extent of wear.

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