The Banana Guage Model 211
Dry Film Thickness Measurement Magnetic

  • The banana gauge works on the principle of magnetic resistance, by means of a small magnet and a tensioned spring.
  • It can therefore only be used on Ferrous substrates. Calibration is vitally important in order to gain accurate Dry Film Thickness readings (DFT).
  • The calibration should ideally be carried out on a blasted surface with a profile similar to that of the painted substrate.

How to calibrate Bana Guage
Calibration process is detailed below:

  • The banana gauge is placed firmly on the bare steel surface, with the magnet end placed directly on a thin plastic “shim” of a known thickness, which is measured in microns. (Older shims have measurements in thousandths of an inch)
  • The tensioning wheel is then pushed slowly forward until it can go no further. (The magnet can be clearly heard to make contact with the surface)
  • The gauge wheel is then (very slowly and carefully) reversed; until such time that the magnet lifts from the substrate. The gauge can then be read, giving a reading of the DFT.
  • Should the reading differ from the known thickness of the shim, the gauge should be rotated back to the zero point, and the scale should be adjusted by holding the black wheel in position, and simultaneously moving the thin steel calibration strip up or down according to requirements. If the initial reading is ess than the shim thickness, the scale would have to be moved up.
  • Alternately, a reading greater than that of the shim would require the scale to be moved down. The calibration process should then be repeated as many times as is required, until the correct thickness reading of the relevant shim is achieved.