Transducers

[Jan]

All transducer designs have the elements in a resin.


This resin must have the same sound properties as water to get the best results.


Aparently there is just one such resin and that one is difficult to use.


Can anyone explain to me why I cannot let the 'working' side of the element touch the water, in other words no resin on the side of the element that is in contact with the water ?


I could imagine that the ceramic element will not be destroyed when getting wet.


As far as I know most ceramic materials will not be harmed by water.


As long I make sure that there are no airpockets on the backside of the element the extra pressure from the water will no crack the element.


Anyone ideas about this ?


Best regards, Jan

[jaime]

Re: Transducers

Has anybody thought about building a "greenhouse" structure (Think of the images that come to mind when you are watching scientists work with biological germs) that would be void of air by attaching a vacuum to it. Wouldn't that suck the air bubbles out of the resin solution while you are pouring it?


>All transducer designs have the elements in a resin.


>This resin must have the same sound properties as water to get the best results.


>Aparently there is just one such resin and that one is difficult to use.


>Can anyone explain to me why I cannot let the 'working' side of the element touch the water, in other words no resin on the side of the element that is in contact with the water ?


>I could imagine that the ceramic element will not be destroyed when getting wet.


>As far as I know most ceramic materials will not be harmed by water.


>As long I make sure that there are no airpockets on the backside of the element the extra pressure from the water will no crack the element.


>Anyone ideas about this ?


>Best regards, Jan

[Jan]

Re: Transducers

I toyed with the idea.


Not so much to get the bubbles out but more because a vacuum is a bad sound conductor.


On of the problems is the so called "ringing" of the transducers.


I was thinking that a vacuum could solve this problem.


However, vacuum must be quite larges and there may be no contact between elements and frame..... and that is a major problem.. ;-)


So I left it.


To get the bubbles out one has to create a very strong vacuum,


I believe that someone on the forum said that the vacuum should be large enough so that water boils at room temperature.... we are talking heavy duty pumps here.


I'll stick to cork, found some nice smooth 3mm thick cork sheets.


I will use that and see what happens.


.... still wondering if water will destroy the elements tough....


Best regards


Jan

[Jim]

Re: Vacuum and bubbles

>Has anybody thought about building a "greenhouse" structure (Think of the images that come to mind when you are watching scientists work with biological germs) that would be void of air by attaching a vacuum to it. Wouldn't that suck the air bubbles out of the resin solution while you are pouring it?


Greetings from a soon-to-be constructor of a SSS unit.


YES, putting the resin in a vacuum is a standard method of removing bubbles from any potting compound. The enclosure is called a "Bell jar" and must be pumped to VERY high vacuum levels (29+ inches of mercury) before the curing process. Any trapped air bubble in the resin gets very large in the vacuum and floats to the top. Depending on the product, the vacuum is held until the bubbles stop rising (Bell jar with a window) and then let the air back in, shrinking any remaining bubbles to microscopic size. This usually requires a special "rotary vane" vacuum pump. Care must be taken to thoroughly clean ALL foreign matter from the assembly first(solder flux, oil, fingerprints etc.) or the contaminants will form a continuous stream of bubbles into the vacuum (outgassing). I hope this helps!


Jim


>>Can anyone explain to me why I cannot let the 'working' side of the element touch the water, in other words no resin on the side of the element that is in contact with the water ?


>>I could imagine that the ceramic element will not be destroyed when getting wet.


>>As far as I know most ceramic materials will not be harmed by water.


>>As long I make sure that there are no airpockets on the backside of the element the extra pressure from the water will no crack the element.


>>Anyone ideas about this ?


>>Best regards, Jan


The ceramic resonators have a thin metallic coating on each face of the wafer that would be subject to corrosion if left in contact with water. Also, the outer face is an active electrode that would be shorted out if not insulated by the resin.


Jim