FAQ in coating thickness measurement



Which substrate should be measured?

  • Steel and iron using Coating Thickness Gauges marked with an "F" (Ferrous), e.g. Surfix® F. All non-magnetic coatings can also be measured, e.g. paint, enamels, plastics, zinc, brass, chrome etc.
  • Non-ferrous metals such as aluminium, brass, zinc die casting etc. using Coating Thickness Gauges marked with an "N" (Non-ferrous), e.g. Surfix® N. All electrical insulating coatings can also be measured such as paint enamel, plastics, anodised coatings etc.
  • Our combined instruments marked with an "FN", e.g. Surfix® FN, can be used for both cases of application. They automatically recognize the substrate and measure the correct coating thickness

Are coatings to be measured on small components such as wires, washers, nuts, screw-heads etc.?

Exact probe positioning on the test object must be observed with measurements on small components in order to obtain the accuracy achieved by calibration. In many cases however, this cannot be produced by hand. The probe can be sufficiently well positioned on small components using our probe guide in order to guarantee the measurement accuracy of the Instrument.

When are instruments used with integrated probes or separate probes?

Coating thickness gauges with integrated probes are suitable for quick measurements on large area objects such as car bodies, hulls of ships, panels, washing machines, tubes etc. due to single hand Operation.

Gauges with separate probes can be used on large surface objects as well as on small components. Separate probes are also better suited for measurements on positions difficult to access. Our probe guide is the ideal tool for our separate probes to measure very small components such as screw heads, washers, nuts etc., using a separate probe.

How large should the measurement range be for the instrument?

An instrument with the corresponding measurement range should be selected depending on the coating thickness to be measured.

Note: If very thin thicknesses are to be measured, e.g. 50µm, then both probe and gauge should be selected with a small measurement range. Instruments with measurement ranges greater than 1,500µm produce inaccurate readings when used for measuring thin coatings.

How accurate should the measurement instrument be?

There are coating thickness gauges available with different measurement uncertainties depending on specific requirements. The measurement uncertainty of coating thickness gauges is always specified with two values:

an absolute value in μm and a relative value in %. The measurement ranges and the measurement uncertainty of our instruments are as follows (1 μm = 0.04 mils):



model range accuracy
Surfix® Pro S 
with FN 0.2
0 – 200 μm ±(0.7 μm + 1% of reading)
Surfix® Pro S 
with FN1.5, F1.5, N1.5, FN1.5R, F1.5R, FN1.5/90°
0 – 1,500 μm ±(1 μm + 1% of reading)
Surfix® Pro S 
with FN3.5, F3.5
0 – 3,500/3.000 μm ±(2 μm + 1% of reading)
Surfix® Pro S 
with F10
0 – 10 μm ±(3 μm + 1% of reading)
Surfix® S 
with FN0.2
0 – 200 μm ±(0.7 μm + 1% of reading)
Surfix® S 
with FN1.5, F1.5, N1.5, FN1.5R, F1.5R, FN1.5/90°
0 – 1,500 μm ±(1 μm + 1% of reading)
Surfix® S 
with FN3.5, F3.5
0 – 3,500/3,000 μm ±(2 μm + 1% of reading)
Surfix® S 
with F10
0 – 10 μm ±(3 μm + 1% of reading)
Surfix® 0 – 1,500 μm ±(1 μm + 1% of reading)
Pocket Surfix® 0 – 1,500 μm ±(1 μm + 1% of reading)
Surfix® easy 0 – 3,500/3,000 μm ± 3 μm oder ± 3% of reading, whichever is greater 
PaintCheck 0 – 2,000 μm ±(5 μm + 5% of reading)

Is a statistical evaluation of the measurement values required?

A statistical evaluation of the measurement values is imperative for an optimum assessment of quality:

  • number of measurement values
  • average value
  • standard deviation
  • maximum and minimum measurement range

 The Surfix® S basic  and Surfix® basic do not have the statistic evaluation  function.

Is measurement value storage required as well as an interface for subsequent transfer of measurement values to a printer or computer?

The instruments must be able to store the measurement values and have an interface in order to document these values on a printer or  a computer.

All Surfix® Pro S,Surfix® S, Surfix® and Pocket-Surfix® have a data memory and also an infrared  interface for wireless data  transfer (refer to "Overview Table" and  the “Technical Specifications" of each instrument).

Data memory and computer interface are not available with the Surfix® S basic and Surfix® Basic.

Is software required for data transfer with statistical evaluation of the measurement values as well as graphics presentation of trend and frequency, to a computer?

There are two different extensive software versions available:


  • FixSoft , a data transfer program for instrument versions Surfix Pro® S, Surfix® S, Surf ix® and Pocket Surfix®.

The measurement values are transferred in a pre-compiled template in Microsoft ExceI together with a histogram and a trend presentation. Specific customer data can also be added at a later time. e.g. date, batch details, name of company and person testing etc. The template can be changed by a user having a knowledge of Excel

  • ProSoft, a user-friendly data transfer program in English for the Surfix Pro® S. 

ProSoft is a database program for data administration and management. It is able to manage all measurement sets, or individual sets, stored in SurfixPro®. Any number of measurement sets can be transferred depending on the size of the computer. The individual measurement sets are displayed as a selection list. The selected file is displayed in separate windows. The measurement values of the individual measurement set are displayed as well as their statistic values, limit values and offset values . The histogram is presented, via the measurement values, in the range of +/-3 standard deviations. Trend graphics present all measurement values relative to the average value. The measurement values can be displayed in µm or mils. Raw data remains unchanged.

A free demonstration version of ProSoft can be downloaded.


Must measurements be carried out inside tubes or positions difficult to access such as in grooves or recesses?

For measurements in tubes or grooves you can use either the gauges Surfix® Pro S or Surfix® S together with probe probe FN 1,5/90°.This special probe enables measurements to be made on tubes having an inside diameter greater than 13 mm. Groove bases can be measured down to a gap width  of 8mm.

After removing of the black attachment foot of the standard probe you can measure within groove bases down to a gap width of 5 mm.

Should measurements be made on hot surfaces up to 300°C?

Surface coating thickness measurements can be carried out up to 300°C depending on the attachment foot of the standard probe for the Surfix® Pro S, Surfix® S and Surfix®. Probe contact on a hot surface should not be longer than 5 seconds. The probe must be cooled before the next measurement, e.g. by placing the probe on a cool surface.

The standard  probe  (measurement  range: 0 … 1,500µm) of the above mentioned instruments can withstand a temperature of up to 100°C.

The standard probe can withstand temperatures up to 150°C with the temperature resistive beige attachment foot (option) an 'is attached by a screw connection replacing the black attachment foot.

The standard probe can withstand temperatures  up to 300°C with a special temperature  resistive attachment foot. This reduces the measurement  range to 0 … 1,100µm, and can easily used by replacing the black attachment foot.

Should the coating thickness continually be measured without lifting the probe?

Very often differences in thickness are required to be detected quickly when carrying out measurements on large areas. In doing this, the probe scans the surface without having to be lifted after every measurement. The Surfix® Pro S has a "continuous mode" and acquires the measurement values with a maximum measurement rate of 180 measurements per minute. It stores these values, statistically evaluates them and, if required, transfers them (wireless) to a PC