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Hello, my name is Nina Giombetti

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and I’m a sales engineer for Olympus Ultrasonic Thickness Gages.

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Today, we are going to discuss

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the differences between Echo to Echo and

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Thru-Coat measurements on the 38DL PLUS.

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The 38DL PLUS has two unique features

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for measuring the remaining wall thickness of pipes,

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tanks or other metal material

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that may be externally painted or coated.

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In this discussion I am going to be using a thin piece of plastic

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to simulate a coating thickness.

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The first feature is called Echo to Echo.

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In this feature the 38DL PLUS

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measures the time of flight

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between multiple back wall reflections within the metal

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to display the true metal thickness

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underneath the painted or coated surface.

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Echo-to Echo is the most common method of measuring

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remaining wall thickness on materials

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that are painted or coated.

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A limitation of this feature

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is that when the internal surface becomes extremely eroded or corroded

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multiple back wall echoes may not exist,

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as displayed in this signal here.

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Another limitation of Echo to Echo

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concerns thick materials,

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where material attenuation and irregular back wall surface conditions

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make it difficult to get two back wall echoes to occur.

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On materials over 15 millimeters

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there can be echo interference

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of unwanted mode converted echoes,

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which occur between the first and second back wall echoes.

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Here I am coupled to a 20 millimeters test block

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and the gage is making detection of the first back wall echo

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but the second back wall echo is very low in amplitude

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and difficult to measure.

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The last limitation regarding Echo to Echo

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concerns measuring thin materials,

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it is extremely difficult or impossible

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to separate the time of flight between multiple back wall echoes

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when the wall thickness is below 2.5 millimeters.

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In this case here we are coupled

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to a 1 millimeter test block

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and you cannot clearly separate the time of flight

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between multiple back wall echoes.

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The second feature the 38DL PLUS has

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to measure the remaining wall thickness

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for pipes or tanks that may be externally painted or coated

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is called Thru-Coat.

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In this technique the gage uses

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a single back wall echo to measure

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both the coating thickness

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and the steel thickness at the same time.

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The advantages of Thru-Coat

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are that it can make proper thickness measurements

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when multiple back wall echoes do not exist

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or when measuring thick and thin materials

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as demonstrated here.

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Here is a Thru-Coat measurement

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when multiple back wall echoes do not exist.

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Here is a Thru-coat measurement

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on a 20 millimeter test block.

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Here is a Thru-coat measurement

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on a 1 millimeter test block.

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The limitations of Thru-Coat

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are it may not work properly

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If the thickness of the coating

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is below 0.125 millimeters

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or if the external coated surface is rough or irregular

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it may be difficult for Thru-Coat to resolve

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the thickness of the coating

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and the thickness of the steel.

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When measuring a painted material

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if Thru-Coat can not resolve the coating

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and steel thickness properly

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then the thickness value of the coating

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will be blank and the thickness of the material

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will be incorrect.

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The truly unique feature of the Thru-Coat transducers

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are that they can be used in Thru-Coat mode

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where they can measure the thickness of the coating

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and the thickness of the steel using a single back wall echo.

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These transducers can also be used

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in Echo to Echo mode

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where they will measure the true metal thickness

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using a multiple back wall echoes

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or in standard measurement mode,

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measuring to the first back wall echo.

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This completes the discussion

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of the differences of Echo to Echo

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and Thru-Coat measurements on the 38DLPLUS.

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For more information, please visit our website

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at www.olympus-ims.com,

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or contact your local sales representative.