PosiTector 200
PosiTector 200 Measuring Rough Coating Thickness
PosiTector 200 coating thickness gages utilize proven ultrasound technology to measure coatings applied to a variety of non-metal substrates. It sends a pulse through the coating, listens for echoes from layer interfaces or the substrate, and calculates coating thickness from those echoes.
The PosiTector 200 is factory optimized to measure most coatings right-out-of-the-box. Simply turn it on, and measure.
Coatings applied over non-metal substrates, such as wood, concrete, and plastic, commonly have some surface roughness or texture. That texture can be deliberate for functional or aesthetic reasons, or inherent to the substrate.
Measuring these coatings can be a challenge for any measurement method, and ultrasonic testing is no exception. By design, the PosiTector 200 is well equipped to handle these situations.
Surface roughness can generate loud near-surface echoes that sometimes look like poor repeatability or cause unexpectedly low values, depending on the texture.
When the PosiTector 200’s probe is lowered, it rests on the peaks and attempts to measure the total thickness. Low values result from the ultrasonic pulse reflecting off the surface roughness (20 microns), rather than the substrate (75 microns). (animation)
By default, the PosiTector 200 searches for the loudest ultrasonic echo within its measurement range and reports it as the coating thickness. Typically, the loudest echoes are generated by reflections off the substrate, or at the interface between two dissimilar coating layers. In multi-layer mode, the thicknesses associated with the loudest echoes are reported as individual layer thicknesses. For most measurement applications, and particularly when measuring smooth, polymer coatings, this method provides accurate readings of the total coating thickness and individual layers without any setup or adjustment required.
Applications with surface roughness, on the other hand, can generate loud, unwanted reflections near the surface, causing the instrument to report the distance between the probe and the valleys of the surface profile instead of the coating thickness. There are two options to overcome this challenge: the innovative Max Thick Mode, or increasing the Low Range.
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 Low Range. Since there will inevitably be some small echoes from within the substrate, only echoes above a preset threshold will be reported.
On PosiTector 200 Advanced models, this threshold can be adjusted from the Graphic Display mode. Simply choose the threshold option and use the plus and minus buttons to adjust the minimum reflection size that should be reported. The instrument will report the deepest echo above this threshold setting.
For more information about Max Thick Mode, read the article linked in the description.
Another way to prevent these occasional low values is with a simple change to the instrument’s Low Range setting.
PosiTector 200 B models have a default measurement range of 25 to 760 microns. These values can be adjusted to change the minimum and maximum thickness reported. The high value rarely needs adjustment, but increasing the low limit helps ignore surface‑roughness reflections.
To adjust the range, press the center button to access the menu. Open the Cal Settings menu, then select Set Range. If using a PosiTector Advanced gage body, a graphics display will appear on screen—use the up and down buttons to highlight the Lo option. On a PosiTector Standard gage body, a simple Lo/High setting screen will be displayed. With Lo selected, press the plus or minus buttons to adjust the Low Range setting.
In this example, we want to ignore the 36-micron surface texture, so we increase the Low Range above the default 25 microns. Now, within the new measurement range of 50 to 760 microns, the 36-micron echo is ignored, and the next loudest echo is reported. Repeated measurements confirm that the PosiTector 200 is no longer influenced by surface texture.
By increasing the Low Range, we effectively tell the gage to ignore the effects of surface roughness because the PosiTector 200 can only report thickness values within its measurement range.
With Max Thick Mode and range adjustment, The PosiTector 200 makes reliable, repeatable thickness measurements on rough coatings—quickly and confidently.
For more information about the PosiTector 200, visit defelsko.com/200