Ref: Air Gap Tool

Rotor-Stator Gap Measurement - Wireless

  • Long insertion depth, with Adjustable insertion stops
  • Measuring range : 10 - 25 mm
  • High resolution (25µm)
  • Easy Set up and operation
  • Calibration and tare function
  • Values are displayed and stored on tablet or smartphone (app provided)
  • All metal construction
  • Alimentation : batterie rechargeable - autonomie: 4h
  • Replaceable target springs
  • calibration and tare functions

Download the product sheet



Air Gap Tool is a simple, fast, and accurate tool designed for static alignment in large-scale hydro generators. It can be used at the time of initial installation and during re-assembly after maintenance procedures. Air Gap Tool is easily positioned at predetermined locations between the stator core and rotor poles. Air gap distance is accurately measured, and the values are displayed on a tablet or smartphone using the provided App. The Air gap tool is simple to use and configurable with unencumbered mobility. It provides usable data and measurement you can trust. It reduces operational costs through faster maintenance time, hence reduced downtime.


Measuring gap 10 - 25 mm
Resolution 25 µm
Operating and storage Temperature 0-70ºC
Value display Tablet or smartphone
Indicators Run, Calibrate
Power supply 100-240VAC, 50-60 Hz


As shown below, the steel spring targets are deflected by the rotor and stator when the instrument is inserted in the gap between them. As the rotor stator gap varies, the sensor will detect a change in the distance between the two springs and vary the output on the digital display to indicate the rotor-stator gap.

Stops are provided for the user to set an insertion depth. This is important as the gap between misaligned rotor-stator assemblies can change with the depth that the measurement is made.


The GMS-750RS is calibrated at the factory prior to shipment. Field calibration is also possible. The only requirement is to be able to accurately mimic a 0.250”, 0.375”, 0.750” and 1" rotor-stator gap. This can be accomplished with a granite surface block, appropriate precision ground spacers, a flat metal plate and the ability to compress the target springs with the flat metal plate (some force is required).



  • Rotor gap measurement during maintenance of hydro-powerplants
Eddy Current
Etendue de mesure linéaire
20 mm
Rotor-Stator Gap

Calibration set

Calibration set

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GMS-750RS - Rotor-Stator Gap Measurement


Rotor-Stator Gap Measurement
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