The high quality Olympus Ultrasonic Thickness Gauges we employ have an accuracy of near 0.001 in., which is greatly dependent upon the equipment employed and operator experience.  Most errors in measurement, on the other hand, often relate to low cost equipment and/or an inexperienced operator.  Performed properly, a wall thickness measurement using ultrasound is equally accurate to a quality dial caliper.  Calibration to standards representative of the material being examined is required initially when setting up and then periodically during the inspection process.  Materials such as carbon steel, galvanized steel, brass, stainless steel, and copper are the most common subjects and are relatively easy to test.

Cast iron and ductile iron, due to their rough internal and external surface textures, grain structure, and due to their natural porosity of the metal, absorb more of the sound signal to make measurement far more difficult.  In addition, sound velocity through such metals can vary from section to section, making measurement far less accurate by up to 20%.  Concrete and transite pipe cannot be tested ultrasonically.