TESTING & MEASUREMENT
predestined for the measurement of very thin single and multiple layer systems as well as for the analysis of complex metal alloys .
Nevertheless , there are applications where the use of the proportional counter tube offers the optimal solution . It is the cost-effective entry point when it comes to routine measurements of known coating systems or alloys . Precise results are obtained for coating thickness measurements in the range of 0.1 – 50 µ m ( depending on the coating system ). If elements are not too close together , as with ZnNi and AuAgCu coatings , material analysis can also be conducted without any problems .
In contrast , closely spaced peaks such as gold and platinum can be analyzed with high separation accuracy using the Si PIN diode and the SDD .
In terms of its design , the proportional counter tube has the following advantages : the active detector area is typically 10 to 100 times larger than that of a semiconductor detector . In addition , it has a slightly curved window . This allows a much larger solid angle to be covered by the detector , much more fluorescence radiation to be detected , and a high count rate to be achieved . Thus , this type of detector is less sensitive to the test part alignment to the detector , the measurement distance setting and the sample geometry .
The Advantage when Large Measuring Distance is Needed : This brings particular advantages for measurements of complex-shaped samples and recesses when a measuring distance of more than 20 mm is required . If the thickness of the zinc layer is measured at an angle of approximately 6 cm , the strengths of the proportional counter tube
come to bear significantly . With a measured mean value of 21.4 µ m , the standard deviation is only 0.2 µ m , the coefficient of variation 0.9 %. To achieve the same measurement result using a Si PIN diode , the measurement time would have to be increased twelvefold ( see table ).
The Advantage when a Small Measuring Spot is Needed : If the layer thickness and composition of simpler layer
systems on smaller samples such as plug contacts needs to be determined , correspondingly small measuring spots of approx . 0.1 mm are required . The proportional counter tube is also the optimum detector choice in many cases of this kind . For example , compared to the other detector types , the proportional counter tube achieves the same precision with a shorter measurement time when measuring the thickness of the gold layer on a plug contact .
Advantage of Measuring with Fischer Measurement Technology : The Fischer measurement software features the inhouse developed drift compensation as standard to achieve consistently reliable measurement results . This gives the proportional counter tube unique stability . The software automatically corrects a possibly occurring drift of the peak position in the spectrum and thus prevents falsification of the results , especially with critical peak overlays .
Conclusion : The proportional counter tube is the cost-effective entry for coating thickness measurements in the range of 0.1 – 50 µ m ( depending on the coating system ), as well as analysis of elements that are spaced apart . If a large measuring distance of more than 20 mm has to be handled , the proportional counter tube shows its strengths . Due to the very large active detector area as well as the slight curvature of the window , a high count rate is achieved even in such cases since a large amount of fluorescence radiation is detected by the detector . The drift compensation developed by Fischer ensures that consistently reliable measurement results are obtained .
To find out more please contact the Fischer Instrumentation team at : -
Telephone : + 44 ( 0 ) 1386 577370 Email : mail @ fischergb . co . uk Visit : www . fischerinstrumentation . co . uk
48 DECEMBER 2021 twitter : @ surfaceworldmag