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CG204-en-GB_v2.3 5/15
10
Two-point calibration
This method requires the use of two films. The thicker film should be, if possible, 1.5 times as thick
as the thinner one. For best results, the expected thickness should be between the two calibration
values.
This method is especially suitable for taking high-precision readings. It is advisable to take a mean
several times. This considerably reduces the effect of scattering which occurs during calibration of
the upper and lower values.
1. Perform a Zero-point calibration (previously described)
2. Enable Calibration mode in the Options Programming Menu.
3. Perform a One-point calibration (as previously described) on the thin calibration film reference.
4. Repeat step 3 using a thicker calibration film (997m for example).
5. Turn off the meter to save the measured values.
Calibration Notes:
1. The thickness of the calibration films should be roughly equivalent to the estimated coating
thickness to be measured.
2. Calibration can be performed as often as necessary. Old calibration data will be overwritten
but the ZERO calibration data remains in memory until another zero point calibration is
made.
CalibratingforShot‐blastedsurfaces
Thephysicalnatureofshot‐blastedsurfacesresultsinhigherthannormalcoatingthicknessreadings.The
meanthicknessoverthepeakscanbedeterminedasfollows:
1. Themetershouldbecalibratedaccordingtothecalibrationinstructions.Useasmoothcalibration
samplewiththesamecurvatureradiusandthesamesubstrate
asthedevicetobetested.
2. Takeapprox.10readingsontheuncoated,shot‐blastedsampletoproducethemeanvalueXo.
3. Takeanadditional10readingsonthecoated,shotblastedtestsampletoproducethemeanvalueXm
4. Thedifferencebetweenthetwomeanvalues
isthemeancoatingthicknessXeffoverthepeaks.The
greaterstandarddeviation‘S’ofthetwovaluesXmandXoshouldalsobetakenintoconsideration:Xeff
=(Xm‐Xo)±S
NOTE:Forcoatingsthickerthan300µm,theinfluenceofroughnessgenerallyisofnoimportanceand
thereforeitisnotnecessarytoapplytheabovecalibrationmethods.
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