Method A:
(suitable for roughnesses with Rz smaller than 20μm)

Zero the instrument.
Carry out two-point calibration.
Position the probe approximately 10 times on the rough surface to carry out zeroing.
Position the probe approximately 5 times for "foil calibration".
You can now measure. Position the probe a number of times.
The average value corresponds to the average coating thickness over the peaks.
 

Method B:

Four step method

(suitable for roughnesses with Rz greater than 20μm)

1. Instrument calibration on a smooth surface having the same shape and the same type of steel as the coated rough measurement object (one-point calibration or two-point calibration).
2. Determination of the roughness effect.
   Position the probe approximately 10 times on the rough uncoated measurement object and form the average value
   x₀ ± s₀ {x_zero ± standard deviation_Zero} from the measurement values. This average value x₀ is a measure for the roughness effect on the Coating Thickness Gauge. You can also use the statistic function of the instrument for averaging.
3. Measurement of the coating thickness on the rough surface.
   Position the probe approximately 5 to 10 times on the coating to be measured. Determine the average value x_0+C {x_zero+coating} from the measurement values as described in Point 2.
   This average value x_0+C is produced from the coating thickness plus the roughness effect.
4. Calculate the difference from the average values x_0+C - x₀.
   The difference is the average coating thickness x_C over the peaks.

from Point 2, e.g.

x₀ ± s₀ = 15μm ± 5μm

from Point 3, e.g.

x_0+C     = 80μm

from Point 4, e.g.

x_C = (x_0+C - x₀) ± s₀ ± instrument tolerance
x_C = (80μm – 15μm) ±5μm ±(1μm + 1% of the measurement value)
x_C = 65μm ± 7μm