S. Berliner, III's berliner-ultrasonics.org Ultrasonics Page 1A keywords = "Berliner III Berlin ultrasonic processing cavitate cavitating cavitation cleaning fluid filtration home.att.net"
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S. Berliner, III
Consultant in Ultrasonic Processing
"changing materials with high-intensity sound"


also see
Keywords (Applications) Index

[consultation is on a fee basis]

Specializing in brainstorming and devil's disciplery for new products and
reverse engineering and product improvement for existing products.


Technical and Historical Writer, Oral Historian
Popularizer of Science and Technology  

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Ultrasonics Page 1A


PLEASE NOTE:  If some internal links refuse to work,
please click on Back and scroll down.

Ultrasonics Index
    Linked Alphabetical Index

On the main Ultrasonics Page:
    Applications List.
    Probe-type Ultrasonic Processing Equipment.
    Brain Storming - bright ideas, pipe dreams, pie-in-the-sky?

On Ultrasonics Page A
        (A Layperson's Explanation of a Complex Letterhead).

On Ultrasonics Page 1 (the preceding page):
        (A Non-Technical Explanation of "Cold Boiling"
            moved from the preceding page 12 Feb 00).

    TUBULAR HORNS (Radial Radiators).
    CARE of TIPS (Radiating Faces).

On Ultrasonics Page 1A (this page):
    Free Bubbling.
    Bubble Entrapment.
    Foaming and Aerosoling - moved 28 May 02 to Page 4.
    Call for Contributions for Book.

On Ultrasonics Page 2 (the next page):
    More on Cavitation.
            SINTERING, SLIPS].

On Ultrasonics Page 3:
    Keywords (Applications) Index.
    What's New?

On Ultrasonics Page 4:
    Misting, Particle Creation and Sizing.
    Threshold of Cavitation.
    Ultrasonics and Nuclear Fusion.
    Quick Links for Ultrasonic Probe Manufacturers (moved 10 Jul 2002).

On Ultrasonics Page 4a:
    Foaming and Aerosoling - moved 28 May 02 from Page 1A         and moved again to Page 4a on 10 Oct 04.
    Ultrasonic Propulsion (Propulsive Force) - Moving Material - moved to Page 4a on 10 Oct 04.
    Ultrasonic Fountains - Atomization, Nebulization, Humidification,
        Misting, Particle Creation and Sizing - moved to Page 4a on 10 Oct 04.
    More about Probe-type Ultrasonic Processing Equipment.
        Cooling Samples.

On the Ultrasonic Cleaning Page:
    ULTRASONIC CLEANING {in process}.
    Immersible Transducers.
    What's New?

    ULTRASONICS GLOSSARY {in process}.

    Ultrasonic Bibliography Page 1 - Reference Books on Acoustics,
        Vibration, and Sound.
    Ultrasonic Bibliography Page 2 - Sonochemistry.
    Ultrasonic Bibliography Page 3 - Selected Articles.

You are invited to visit the ULTRASONIC INDUSTRY ASSOCIATION home page.

CALL FOR CONTRIBUTIONS:  I am writing a book on "High-Intensity Ultrasonic Technology and Applications", on the practical application of power (high intensity) ultrasonics, the use of ultrasonic energy to change materials.  Contributions are welcome (see below).


Larry Crum's Cavitation Bubble

[image from University of Washington, Applied Physics Laboratory (Lawrence Crum, Ph.D.)
- bubble diameter approximately 1mm]



{This is a DRAFT, only; please substitute reprint PVI-2 for AP-0}

1.  GENERAL - The difference between the terms "intensity" and "power" in probe sonication has been discussed in detail in Applications Primer AP-0, normally appended hereto, q. v.  Power is measured in watts.  It is the energy required to drive the radiating surface of a given horn, at a specified amplitude of vibration, the excursion or stroke, against a specified load, at the fixed resonant frequency of the device to generate cavitation in a liquid.  Intensity is a measure of the energy available per unit volume of liquid and is directly related to amplitude.  It is the intensity of cavitation that determines the effectivity of sonication in disrupting cells, accelerating physical and chemical reactions, degassing, mixing "immiscible" liquids, shearing DNA, disaggregating shale, and so forth, not the total power applied to the system.  Intensity is directly related to the amplitude of the radiating face of the tip or horn.  It is amplitude that must be provided, maintained, and monitored.  Any truly satisfactory ultrasonic liquid processor or cell disruptor must provide controlled amplitude under all varying load conditions within specifications.

1.1  Since the amplification factor of the horn is fixed by its geometry (refer to AP-0), the measurements can be taken from any surface perpendicular to the longitudinal centerline.  Thus, measurements can be taken outside a sealed pressure vessel, even by direct contact, without breaching the vessel.

2.  MEASUREMENT MEANS - Amplitude can be measured by various methods which are mechanical, optical, electrostrictive (piezoelectric or magnetostrictive), ultrasonic, etc., both directly and indirectly.

3.  MECHANICAL MEANS - An accurate, simple, and historically least expensive means to measure tip amplitude is by direct mechanical contact.  A suitably calibrated dial indicator can read amplitude directly from the radiating face.

Figure 1. Mechanical measurement
[Illustration © S. Berliner, III - 1999]

3.1  Originally, the dial indicator was mounted alongside the horn on a fairly rigid bracket which also held an axle for a lever projecting under the radiating face.  The tip and lever were under the liquid surface and the indicator above.  This complexity was occasioned by the inability of early ultrasonic disruptors/processors to maintain amplitude unloaded.  With accurate constant smplitude control, these measurements can now be made in air, with the horn or tip unloaded.  This technique is shown in Figure 1.  The dial indicator method can be used quite effectively on large horns at moderately high amplitudes within the operating range of a dial indicator.  However, the smaller the bulk of the horn and the diameter of the radiating face, the more the dial indicator gearing loads the resonant device and affects the output.  In addition, too much amplitude may destroy the dial indicator bearings and gears.  However, for those who wish to use this technique, the dial indicator is best nulled while the ultrasonic device is operating and the reading taken when the device is turned off.  This will minimize erratic readings made while trying to null the indicator; it will prove amazing how sensitive even the most rigid indicator mounting will be.  For this reason, it is absolutely critical for good results that the convertor (transducer housing) and the dial indicator be rigidly secured to a common, rigid mechanical ground.  A 3" (76mm) or heavier drill press column and base, readily available from machine tool vendors, with very heavy clamps for the convertor and indicator, is recommended.  If the mountings are not heavy, rigid, and secure, readings will drift.

3.2  If the rear surface of the horn projects beyond the front driver and convertor case diameter sufficiently to provide axial access for the dial indicator tip, a reading can be made directly from the top of the rear surface with the indicator upright.  The horn amplification factor must be known accurately and verified.  Merely taking the ratio of the square of the body and tip diameters may not be sufficently accurate for this method.

3.3  The amplitude read is that of rest-to-peak or single amplitude, which must be doubled if comparing to the parameter normally specified, peak-to-peak or double amplitude.  The horn tip merely pushes the indicator tip down and the inertia of the indicator gearing prevents it from returning under spring pressure; the net effect is that the indicator "floats" at the maximum excursion of the horn/tip face.

4.  OPTICAL MEANS - Direct and accurate measurement of radiating face amplitude can also be made without in any way affecting the action of the ultrasonic device or the resultant process by optical means. Direct observation by microscope, indirect observation by electronically-amplified and computer-analysed image processors, interferometer measurements, and other means are available.  Optical measurements may be taken both with the tip vibrating in air under no load or under clear or translucent liquid in a transparent vessel.  It is even possible to "see" inside an opaque suspension.

Figure 2. Optical Measurement
[Illustration © S. Berliner, III - 1999]

4.1  A simple, inexpensive field microscope with a calibrated reticle is the least expensive method of optical amplitude determination, as shown in Figure 2.  Since the magnitude of vibration at the radiating face is usually in the order of 1 to 250 Ám (micrometers) and the microscope axis is at right angles to the axis of the convertor/horn, errors due to parallax or refraction through the liquid/glass interface are negligible.  The convertor should be set up in a rigid stand with the horn hanging free beneath it.  A 100X field microscope with calibrated reticle is oriented perdendicular to the axis of the convertor and horn such that the reticle scale is vertical and the longitudinal (vertical) displacement of the tip can be read directly through the calibrated eyepiece (ocular lens).  The microscope is focused on, and the measuring scale is zeroed on, the horizontal image of the radiating face (or on a horizontal scratch or mark on the side of the tip immediately adjacent to the face) and the ultrasonic device activated.  The observer sees the edge (or mark) blur and, because of the speed of oscillation, sees two distinct images at each end of the blur.  Since the horn is a resonant body, vibrating from rest, the images seen are the peak amplitudes in the positive and negative mode; that is, the viewer sees that point at which the face stops advancing up or down and starts to return to rest.  These images, then, are those of maximum positive and negative excursion from rest.  The distance measured between these two images is the double amplitude, or peak-to-peak excursion, of the radiating face.

4.2  The microscope image may be electronically amplified and analysed by computerized image processors for greater accuracy and automation.

4.3  As with the mechanical dial indicator method, it is important that the microscope and convertor be rigidly mounted to a common, rigid, mechanical ground.  The drill press stand noted in Para. 3.1 is useful.

[Note:  It has been reported in using the optical method with magnetostrictive transducers that a line voltage can be superimposed over the driving voltage, especially under fluorescent light, possibly resulting in a blurred image, but this problem does not seem to occur with piezoelectric processors.]

5.  OTHER NON-CONTACT MEANS - Magnetostrictive and piezoelectric sensors have been used to determine amplitude.  One of the first methods was to embed a nickel or monel pin in the back surface of a horn, parallel to the axis of the horn, and place a sensing coil around it.  As the pin was accelerated axially, it changed the impedance of the coil.  Piezoelectric wafers can be placed in the stack (new piezoelectric polymer films just introduced at this writing may find use in this manner) and send a signal proportional to amplitude.  Voltage feedback from the driving crystals may also provide a proportional signal.  Laser and microwave interferometers and similar devices can be used to sense high frequency displacement.  X-ray or neutron sources might be combined with interferometry to read amplitude with closed volumes.  Ultrasonic sensors may also be used, provided the frequency is such that it does not interact with that of the device being measured.

6.  EQUIPMENT - The 100-power field microscope with calibrated reticle referenced in Paragraph 4.1 for optical measurement of tip amplitude was imported from Japan by Southern Precision Instruments under their Part Number 1837 and is {was?} available as their Direct Measuring Microscope under Catalog No. N61,193 (on Page 21 in August 1, 1988, Catalog 18N7) from:

Edmund Scientific Co., 101 East Gloucester Pike, Barrington, NJ  08007
tel.:  609-547-6250 or -3488, FAX:  609-573-6295

The dial indicator referenced in Section 3 for direct mechanical measurement of tip amplitude was made in Japan by Mitutoyo as their Model No. 2109, 6 Jewels, Shockproof, rated at 0.001 - 1 mm or Model No. 2119, Jewelled, rated at 0.001 - 5 mm.  The choice of range (1 to 40 mils or 1 to 200 mils) is best determined by the expected amplitude to be measured.  The Model 2109 is desirable for greater accuracy at lower amplitudes; the Model 2119 is chosen for measuring higher amplitudes.  A flat indicator tip was originally used; later both cupped (concave) and broad radius (convex) tips were tried, but flat tips seem best, overall.  It is important to assure perpendicularity such that the horn or sample radiating face doesn't skitter off center.  One source for the dial indicator is {was?}:

MSC Industrial Co., Long Island Division, 151 Sunnyside Blvd., Plainview, NY 11803
tel.:   800-645-7270 or 516-349-7100; local:  800-645-7008 or 516-645-7270;
FAX:    800-255-5067;   Telex:  221719 SIDTL UR

The metric system model numbers noted did not appear in MSC's last-seen catalog; only English system indicators were listed.

Neither the specific microscope or indicators shown, nor their sources, are critical.  Equivalent or better equipment will serve.

7.  For information regarding any specific processor/disruptor and horn or tip, refer to the referenced primer or contact the author.

© S. Berliner, III 1999/1995/1993 (all rights reserved)

Free Bubbling

Elsewhere on this site, I use the term "Free Bubbling"; it is not a term of art to my knowledge.  By "Free Bubbling", I mean the outgassing of air (or other gas) bubbles from the liquid in which cavitation is to (takes/has taken) place, without the application of ultrasonic energy.  The difference between free bubbling and cavitation bubbles can be easily and dramatically demonstrated.  Observe the bubble formation in the cavitation field in an active tank or in front of the radiating surface of an active, immersed sonicating probe.  Then turn off the power.  The cavitation bubbles will disappear instantly (within one half-cycle of the frequency, far too quickly for you to be misled); any bubbles which then remain and rise out of the bath are air or gas bubbles, degassed from the liquid or created at an air/liquid/object interface.

Bubble Entrapment

These pages speak to degassing of liquids by active cavitation; they have not, however, to date (29 Sep 99), dealt with the opposite phenomenon, Bubble Entrapment.  By this is meant the forcing, by various mechanisms, of bubbles of ambient gas (usually air) under the surface of the liquid being used in treating an object or a liquid being treated.  The degree to which this occurs is directly proportional to the amplitude of vibration of the probe or tank wall (or any vibrating object) at the object/gas/liquid interface (visually somewhat akin to a triple point in metallurgy), as well as inversely to the frequency.

Air Entrapment
[18 Mar 2008 illustration by and © 2008 S. Berliner, III - all rights reserved]

Where a vibrating object breaks the gas/liquid interface, it can drag molecules of gas adhering to its surface under the interface (liquid surface) on the forward (downward) stroke and release them on the reverse stroke.  The further and faster the excursion of the object, the greater the likelihood of entrapment.  In extreme cases, usually limited to probe sonication, although not impossible in tank cleaning, this can result in foaming of the liquid and loss of transmission of ultrasonic energy.

Foaming and Aerosoling

When a foam is generated in a lab sample, it interposes bubbles between the radiating surface and the body of the liquid to be treated or in which treatment is to occur.  This is somewhat akin to "blanketing" but is the result of gas bubbles, not cavitation bubbles, interfering with free radiation of acoustic energy into the bath.  It is a self-limiting process.   rev.gif (03 Jun 2015)

Once a foam has been created, especially in viscous liquids, it becomes necessary to stop onication and degas the liquid.  In some cases, at low viscosity, bubbles may rise against gravity and escape through the liquid surface.  If, however, they persist in the bath, short bursts of energy (pulsing), with long rest times between, may be sufficient to break the foam.  A fine mist of the parent liquid can be sprayed against the foam to break it; ultrasonic nozzles excel at this.  In extreme cases, centrifuging and/or vacuum must be applied or the sample may even have to be discarded.

Similarly, on the reverse stroke, molecules of liquid adhering to the surface of a vibrating object may be dragged above the interface (liquid surface) and released, or even ultrasonically nebulized and driven off balistically, into the atmosphere ("aerosoling").  Obviously, this could pose a significant risk if the liquid is toxic or contains biohazards.  Various techniques beyond the scope of this monograph are available to minimize aerosoling or prevent the escape of the aerosol.

More on this subject and its commercial applications will be found on Ultrasonics page 4.

EXTENDERS (Extender Tips)

Horns are normally made of titanium or aluminum, both of which have a half-wavelength of approximately 5" at 20KHz.  In order to reach into narrow vessels or through necks of vessels or into process streams and such, "extenders" (also called "extender tips") are available from some probe manufacturers.  Horns are normally a half-wavelength long (~5") and extenders are usually made in "Half Wave" and "Full Wave" length increments; they are usually simple cylinders, solid or tapped for a tip.  Solid extenders are actually more than a wavelength increment; they have to be fitted to tapped horns and so are longer than the wavelength increment by the length of the regular replaceable tip in order to maintain resonance.  A Full Wave extender is represented graphically here:

Extender (Full Wave shown)
[Image by and © 2000 S. Berliner, III - all rights reserved.]

Call for Contributions

For the forthcoming book, "High-Intensity Ultrasonic Technology and Applications", on the application of power (high intensity) ultrasonics, the use of ultrasonic energy to change materials (intended for Marcel Dekker's* "Mechanical Engineering Series", edited by Profs. Lynn L. Faulkner and S. Bradford Menkes), I solicit input in the following forms:
  1.  Corporate/Organizational/Personal History.

  2.  Significant Technical Breakthroughs.

  3.  Thumbnail Biographies of Leading Innovators.

  4.  Photographs of Major Representative Equipment, especially of
	New and Unique Items.

  5.  Diagrams of Major Applications and Processes.

and, of course,

  6.  Permission to edit and reproduce the above for publication (with
	the style in which appropriate credit is to be given).

  7.  Reprints of any articles published about equipment and applications.

  8.  Copies of any Patents which you feel cover(ed) outstanding
        innovations in equipment and/or processes.

These are the gut items that will highlight, flesh out, and humanize the otherwise dry facts of ultrasonic cleaning, welding, bonding, joining, cutting, drilling, and the myriad other applications.

This will be a practical text, not so much "how-to" as "what has been done, is being done, and can be done".  I will need illustrations of standard bonding and cleaning processes and special features.  If you wish those you use in your literature to be included in the book, with appropriate credit to you or your firm (as appropriate), of course, please forward copies.

Any illustrative material (photographs and diagrams) should be in camera-ready form.  Xerographic copies are not suitable.  Photographs should be glossy 4"x5" or 8"x10".

Naturally, no guarantee can be given that any material submitted will be included but I want to give a balanced picture of the industry.  I ask that you be selective; please don't just "dump" catalogs on me.

For this book and other work, I am seeking information about Narda Ultrasonics Corporation, a firm which pioneered high-intensity application of ultrasonic energy ca. 1946-1960, and was sold to Dynasonics Corporation of Minnesota in 1965; however, some of the activities appear to have subsumed into Narda Microwave Corporation, which was bought out by the Loral Corporation, which, in turn, was acquired by Lockheed Martin Corporation and so to L-3 Communications Corporation.

[* - Marcel Dekker has been aquired by Taylor & Francis and this project assigned to CRC Press.]

Please note that a far-more detailed explanation of ultrasonic processing, as well as other technical literature, is available at no charge to consultation clients.  However, as what I believe to be a public service, I shall be adding more of my monographs on ultrasonics on this site; watch for them in the index.

You may wish to visit the main ULTRASONICS page, et seq., with more on ultrasonics, as well as the Ultrasonic Cleaning page and the Ultrasonics Glossary page {in process}.

Those persons interested in SONOCHEMISTRY might wish to look at the sonochemistry pages of:
Prof. Kenneth S. Suslick of the University of Illinois at Urbana-Champaign, and
Dr. Takahide Kimura at Shiga University in Japan.

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To tour the Ultrasonics pages in sequence, the arrows take you from the main Ultrasonics Page (with full index) to Pages A, 1, 1A, 2, and 3, Glossary Page, Cleaning Page, and Bibliography Pages 1, 2, 3, and 4 (see Index, above).

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