View source for Ultrasonic Immersion Bath Sensors

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<span style="font-size:1.2em;font-weight:bold;">Ultrasonic immersion bath sensors</span>
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==Schematic configuration==

Immersion bath sensors are similar in design to vertical or [[Ultrasonic Standard Sensors|standard sensors]], although they are slightly longer than sensors for [[Ultrasonic Direct Coupling|direct coupling]]. To ensure watertightness and optimum impedance matching to water, they are usually equipped with special sealing or matching layers, which also serve to protect the [[Ultrasonic Sensors|sensor]] against electrical short circuits. Immersion technique sensors can be used for vertical and oblique (angle) sound transmission and can be partially or completely immersed in water. Technical variants of water or [[Ultrasonic Immersion Bath Technique|immersion coupling]] include flowing water coupling, immersion bath coupling, the so-called puddle technique, and guided and free water jet coupling, also known as [[Squirter Technique|squirter technique]] ('''Fig. 1''') [1].

[[File:US_Tauchbad_Pruefkoepfe-1.jpg]]
{| 
|- valign="top"
|width="50px"|'''Fig. 1''': 
|width="600px"|Variants of the immersion bath technique arrangement with (a) flowing water coupling, (b) immersion technique arrangement, (c) puddle technique, (d) guided and (e) free [[Squirter Technique|squirter technique]] according to [1, 3]
|}

==Examples of implementation==

For flat structures, not only a single [[Ultrasonic Sensors|sensor]] is often used, but rather a sensor field, whereby this arrangement is used in particular for passive scanning, i.e. for a moving test object. Especially for metal or [[Plastics|plastic]] pipes, rotating immersion sensor can also be used, whereby these are fixed at a defined distance [2].

Lead metaniobate transducers (PbNb2O6) have the lowest acoustic impedance of all [[Piezoelectric Ceramic|piezo ceramics]] and, like polyvinylidene fluoride ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PVDF), are particularly suitable for constructing high-resolution immersion technique transducers with extremely short pulses. In PVDF sensors, the damping element consists solely of highly absorbent plastics. At identical frequencies and with the same transducer diameter, highly damped immersion sensors made of PVDF and lead metaniobate, for example, exhibit approximately comparable sensitivity at very short pulses [1].

Piezoelectric plastic films made of PVDF ensure highly effective sound radiation, especially in water and plastics, which is why PVDF is suitable for high-frequency delay line or immersion sensors (''f'' up to 150 MHz) [2, 4].

Due to their acoustic impedance, piezo composites ([[Ultrasonic Composite Sensors|composite sensors]]) are also very well suited for sound radiation in liquids and [[Plastics|plastics]], whereby the plastic filler of the damper should only be moderately filled (impedance). This also allows the production of very broadband immersion technique sensors whose sensitivity is higher than that of [[Piezoelectric Ceramic Transducer|piezoelectric ceramic transducers]]. Examples of immersion technique sensors are shown in '''Fig. 2'''.

[[File:US_Tauchbad_Pruefkoepfe-2.jpg|300px]]
{| 
|- valign="top"
|width="50px"|'''Fig. 2''': 
|width="600px"|(a) 2 MHz composite immersion bath sensor and (b) 5 MHz piezoceramic immersion bath technique sensor from [https://www.sonotec.eu/en/ Fa. SONOTEC Ultraschallsensorik Halle GmbH, Halle (Saale)]
|}

==See also==

* [[Ultrasound Testing|Ultrasound testing]]
* [[Non-destructive Polymer Testing|Non-destructive polymer testing]]
* [[Ultrasonic Direct Coupling|Ultrasonic direct coupling]]
* [[Ultrasonic Immersion Bath Technique|Ultrasonic immersion bath technique]]
* [[Squirter Technique|Squirter technique]]

==References==

{|
|-valign="top"
|[1]
|Deutsch, V., Platte, M., Vogt, M.: Ultraschallprüfung – Grundlagen und industrielle Anwendungen. Springer Verlag, Berlin (1997), (ISBN 3-540-62072-9; siehe [[AMK-Library]] under M 45)
|-valign="top"
|[2]
|Matthies, K. u. a.: Dickenmessung mit Ultraschall. DVS-Verlag GmbH, Berlin, 2. Auflage, (1998), (ISBN 3-87155-940-7; siehe [[AMK-Library]] under M 44)
|-valign="top"
|[3]
|Deutsch, W. A., Deutsch, K., Schuster, V.: Automatisierte Ultraschallprüfanlagen – Überlegungen zu Durchsatz, Überdeckung und Sensorik. DGZfP-Berichtsband 87, FA-Seminar des FA Ultraschall 2003 [https://www.karldeutsch.de/wp-content/uploads/2019/01/SD_1_50-Automatisierte-UT-Anlagen-Durchsatz-%C3%9Cberdeckung-Se%E2%80%A6.pdf Download as pdf]
|-valign="top"
|[4]
|Schuster, V., Lach, M., Platte, M.: Die Qual der Wahl: Welcher Prüfkopf für welchen Einsatz. DGZfP-Jahrestagung „Zerstörungsfreie Werkstoffprüfung“ 2004, Salzburg, Österreich, Sonderdruck Karl Deutsch, SD 1/51 [https://www.ndt.net/search/docs.php3?id=2626 Download as pdf]
|}

[[Category:Acoustic Test Methods_Ultrasonics]]