How Does An Ultrasonic Thickness Gauge Work?
Are you looking for more information about how exactly your small, handheld device can accurately and reliably ascertain the thickness of a given material? If that is the case, then continue reading and you will gain a basic insight into the principles and methods used. This may help you understand your device and utilize the brilliant technology within more effectively.
What is an ultrasonic thickness gauge?
An ultrasonic thickness gauge is any electronic device that uses the emission and reception of sound waves to measure the thickness of a given material. They can come in different shapes and sizes, as well as having vastly different capabilities and usability. Depending on your industry role and requirements, you may find one device is a lot more useful than another because different scenarios may have need of different or multiple functions.
A thickness gauge has two main components; the body and the probe. The probe is connected to the body by an electrical cable, which sends and receives the required data from the body. The body itself contains sensitive and intricately organized computational equipment that is preprogrammed with everything you need to for comprehensive thickness measurement.
How does the gauge work?
The first step is knowing what you need to measure, which sounds simple enough but can be easy to get wrong. Every material has a different internal sound velocity, which is to say that sound travels through different materials at different speeds. This is a vital part of calculating the thickness of a material, because thickness is equal to the echo cycle time divided by the sound velocity. It uses the principles of the basic distance, speed, and time triangle in a much more in depth way.
In order to accurately calculate the thickness, the device needs to know the velocity of the sound within the material you’re measuring. Because this will be unique to the material itself, it is important to calibrate the device you are using to the material you wish to measure. For information about calibration, you can take a look at our YouTube channel that contains videos covering a wide variety of topics. Below, you can see a table outlining a few of the most common engineering materials and their associated internal sound velocities.
|Aluminium||3040 – 6420|
|Brick||3600 – 4200|
|Concrete||3200 – 3700|
|Copper||3560 – 3900|
|Glass||3950 – 5000|
|Iron||3850 – 5130|
|Lead||1160 – 1320|
|Steel||4880 – 5050|
|Wood||3300 – 5000|
After calibrating, your device is ready to measure the specimen with accuracy. The second step is to determine whether or not the surface you need to obtain the thickness of is obscured by a coating of some kind. A coating is considered any material that covers the surface and prevents direct contact between the probe and the surface itself. Examples of coatings can include, but aren’t limited to:
- Lichen, Moss, and plant life
- Seaweed (for underwater/marine measurements)
- And Many Others
If you are using a device equipped with Single Echo, then these layers covering the surface will cause a discrepancy in the measurements and give you inaccurate results. In this scenario, it is important to ensure the surface is scrubbed clean and insulating gel is used to form a clean connection between the probe and the surface.
For devices that can use Echo-Echo and Multiple Echo methods, then the coating is less of a problem and can be worked around. Echo-Echo allows your ultrasonic thickness gauge to ignore a coating up to 1mm thick. Our pioneering Multiple Echo method can ignore up to 6mm thick coatings and with Deep Coat mode enabled, coatings up to 20mm can be ignored.
The measurement process includes the device producing an ultrasonic pulse, which is sent through the material you are measuring. The timing starts when the pulse is initially emitted from the probe and ends when the return echo, which reverberates back through the material after bouncing off the back wall, is detected. See the image (below) for a visual explanation.