PRODUCTS & PROCESSES
TAILOR MADE PROBE
FOR NEW APPLICATION
Measuring the coating thickness of
Sprayable Acoustic Material
Often, tailor made
solutions are necessary
when there is no suitable
technical solution to
measuring a new type of
coating thickness.
A typical example is the
quality control process
for Sprayable Acoustic
Material (SAM) coatings.
In the automotive industry, a great deal of effort
goes into reducing vehicle weight by using lighter
components, while also maximising automated
production. An example is the replacement of
large soundproofing mats in vehicle interiors
with locally and selectively applied SAM coatings.
These locally sprayed layers can be seen in
the passenger footwell (Figure 1). In order to
meet the targets for sound protection, weight,
clearance and cost, the thickness of these
coatings must be carefully monitored.
In addition to its lightness, sprayed-in acoustical
insulation has a further advantage in that it
can be applied precisely
and selectively by robots,
allowing a full automatic
manufacturing process.
Typically, these SAM coatings
are between 2 and 4.5 mm
thick, very often located in
places that are difficult to
reach, and found on top of
either aluminium or steel –
that is, on both ferrous and
non-ferrous substrates.
Figure 1: Locally applied SAM coatings
in the passenger footwell, measured
with DUALSCOPE® FMP40 and FA14 probe
(Daimler AG, Mercedes-Benz Bremen factory)
Figure 2: FA14 probe
(operable with hand-held
FMP series instruments)
No suitable probe has been
available for the stated
coating thickness range.
Probes that were sufficiently
compact had too small a
measuring range, whereas probes that had
sufficient measuring range were too
large. Therefore the FA14 was
developed as a solution for this and
similar applications. This probe
works according to the eddy
current method (DIN EN ISO
2360) but is designed in such a
way that it can be used to measure
non-conductive coatings as well as conductive,
non-magnetisable (e.g. aluminium) and
magnetisable (e.g. steel) base materials.
A measuring range of up to 5mm thickness
is assured on both base materials.
Above and beyond these fundamental specifications, the FA14’s compact elbow design
(Figure 2) also makes it possible to take accurate
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May 2014
readings in very close areas. The sensor has an
external casing with a total diameter of 20 mm,
and its field focus is optimised such that measurements can be taken – without edge influence –
on spots no bigger than the probe itself.
As with all Fischer eddy current probes, the FA14
compensates for