Replica tape has been used to measure the profile of abrasive blasted steel since the late 1960's. Compared to other methods, it has the advantages of ruggedness, relatively low start-up cost, good repeatability and the option of retaining a physical replica of the surface being evaluated. The method is widely used and widely understood. But it is not widely known that surface replicas obtained using Testex Tape contain far more information than just peak height as measured by a micrometer.
Significant data is available through digital imaging. The PosiTector RTR-P captures an image of light passing through the burnished tape which reveals light areas of higher compression (peaks) and dark areas of lower compression (valleys). The gage simply counts the bright spots.