A small part used with single element transducers to slow down the sound pulse to allow precision measurement on thinner materials.

There are two different materials of delay line – acrylic and graphite – and the material you are measuring will affect the material of the delay line you should use.

Acrylic delay lines are suitable for measuring on steel, aluminium, and titanium, with the gauge in either Interface-Echo or Echo-Echo mode; while thin plastics and other similar materials should be measured using a graphite delay line, with the gauge set to Plastic Mode.

Higher frequency single element transducers improve resolution and small flaw detectability.