TESTING & MEASURMENT
Measuring total coating thickness on plastics , concrete , wood & more using Max Thick Mode on the PosiTector 200
The PosiTector ® 200 Coating Thickness Gauge non-destructively measures coating thickness over non-metals including coatings over wood , concrete , plastic , composites and more using proven ultrasonic technology . With the new Max Thick Mode , the PosiTector 200 is easier than ever to use .
Measurement Principle
The PosiTector 200 probe emits an ultrasonic sound pulse that travels into the coating and reflects / echoes from any interface that is different in density , such as the substrate . It measures the time it takes for the sound pulse to travel from the probe to the coating / substrate interface and back . By multiplying this travel time by the velocity of sound through the coating ( which is similar for most polymer coatings ), the thickness of coating ( s ) can be calculated .
While there is almost always a density change at the coating-substrate interface that the PosiTector 200 can detect , density changes between coating layers can also be identified . PosiTector 200 Advanced models can often detect the interface between layers of different or identical coatings , as long as the initial layer is allowed to fully cure before application of the subsequent layer .
Typically , the loudest ultrasonic echo represents the coating-substrate interface , with smaller echoes representing individual layer thicknesses .
Default Mode
The default measurement mode on the PosiTector 200 has been successfully utilised for decades to measure coating thickness on a wide variety of coatings and substrates . The PosiTector 200 searches for the loudest ultrasonic echo within its measurement range , and reports it as the coating thickness . In multi-layer mode , the thicknesses associated with the loudest echoes ( depending on the number of layers selected ) were reported as individual layer thicknesses . For most measurement applications , and particularly when measuring smooth , polymer coatings , this method provided accurate readings of the total coating thickness and individual layers , without any setup or adjustment required .
Applications with surface roughness or many loud echoes near the surface of the coating were sometimes challenging to measure with the PosiTector 200 , because those conditions generated loud , unwanted echoes , often larger and louder than the desired echo form the coating-substrate interface . While increasing the instrument ’ s Lo Range would ignore these unwanted echoes , it is time consuming and is sometimes difficult to make an adjustment that would ignore the unwanted surface echoes , while still measuring thinner areas of applied coating .
Max Thick Mode
When increasing the Lo Range requires an adjustment too close to the expected coating thickness or if a user simply does not want to adjust the range , the NEW Max Thick Mode is optimal .
When Max Thick Mode is enabled , the PosiTector 200 searches for the deepest significant echo instead of the loudest echo . This means that any loud echoes near the surface ( typically caused by surface roughness or a ’ noisy ’ coating system ) are ignored . This mode is often more effective at reporting the total coating thickness at the substrate interface , and eliminates the need to adjust the instrument ' s preset Lo Range . Since there will inevitably be some small echoes from within the substrate , only echoes above a pre-set loudness will be reported . On PosiTector 200 Advanced models , this threshold can be adjusted from the Graphic Display mode .
While Max Thick Mode is enabled and when multiple layers are selected ( PosiTector 200 Advanced only ), the layer thicknesses associated with the deepest ultrasonic echoes are reported .
Note : Max Thick Mode is not recommended for use with thin metal substrates or composites such as carbon fiber or fiberglass .
Conclusion
The PosiTector 200 Ultrasonic Coating Thickness Gage measures coating thickness on non-metals including wood , concrete , plastic and more . For most applications , the NEW Max Thick Mode will give the most accurate readings while eliminating the need to adjust the Lo Range to ignore incoming surface reflections .
A simple gage update adds this functionality to existing PosiTector Standard ( serial numbers 795,375 +) and Advanced ( serial numbers 784,000 +) models .
Contact sales @ dftinstruments . co . uk with specific questions or to request additional information . Telephone : + 44 ( 0 ) 1442 879595 Visit : www . dftinstruments . co . uk
42 MAY 2021 twitter : @ surfaceworldmag