When To Use Thickness Correction; Wire Insulation Cut Into Strands - Thermo Scientific XL2 User Manual

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When to use Thickness Correction

158 Niton XL2 Analyzer User's Guide
Thickness Correction should only be used during the analysis of plastic (polymer) objects. It
has been experimentally verified that the correction algorithm will yield satisfactory results,
for a 60 second minimum testing time, for samples as thin as 0.3mm. Nevertheless, the
recommended range of use of the correction is from 1mm upwards. It is imperative that this
correction is not used for thin films such as single foils and plastic membranes; analysis of thin
films is performed using the Thin Sample Mode. (Contact Contact Thermo Scientific or your
local Niton Analyzers representative for information on this testing mode.)
Whenever possible, one should analyze as thick a sample as available. For example, if the
analyzed object is a piece of heatshrink tubing with wall thickness of 0.3mm, the best way to
analyze it is to obtain several pieces of the tubing (four for example) and stack them like a flat
sandwich, with the thickness correction set to 1.2mm. Doing so makes for faster and more
precise analyses. While it would be possible to analyze just a single layer of the tubing with
correction at 0.3 mm, by stacking several layers we reduce the relative error of measurement
(by a factor approximately equal to the square root of the number of layers). Conversely, when
analyzing thinner samples, we need to extend the measurement time fourfold (by the number
of layers) in order to maintain the same relative error of measurement. We can see how
quickly measurement time would escalate to impractical levels for thinner samples.
Examples: The most frequent instances in which thickness correction would be called for are
analyses of plastic sheeting or plastic insulation on wires and/or cables and heat shrink tubing.
Flat plastic sheeting or plastic enclosures pose no problems. We can either analyze an object
"as is", or stack several layers of it before analysis. Plastic insulation such as that on wiring or
cables requires a little more sophisticated approach. First, the wire must be removed so that
only insulation is analyzed. Then, the insulation should be flattened for analysis, and a
thickness correction should be applied that is equal to double the wall thickness. Alternatively,
if the insulation is stiff, it should be cut lengthwise into strands which are placed on the
indtrument for analysis. The applied thickness correction should be equal to the wall
thickness of the sleeve. Both operations are shown in Figure 37 and Figure 38.
Figure 16.

Wire Insulation Cut Into Strands

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