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4. PRINCIPLES OF OPERATION
The ultrasonic power supply transforms AC line power to a 20 kHz signal that drives a
piezoelectric converter/transducer. This electrical signal is converted by the transducer to a
mechanical vibration due to the characteristics of the internal piezoelectric crystals.
The vibration is amplified and transmitted down the length of the horn/probe where the tip
longitudinally expands and contracts. The distance the tip travels is dependent on the
amplitude selected by the user through the keypad. As you increase the amplitude setting the
ultrasonic processing intensity will increase within your sample.
In liquid, the rapid vibration of the tip causes cavitation - the formation and violent collapse of
microscopic bubbles. The collapse of thousands of cavitation bubbles releases tremendous
energy in the cavitation field. The erosion and shock effect of the collapse of the cavitation
bubble is the primary mechanism of fluid processing.
The probe tip diameter dictates the amount of sample that can be effectively processed. Probes
with smaller tip diameters deliver high intensity ultrasonic processing, but the energy is focused
within a small, concentrated area. Larger tip diameters can process larger volumes, but offer
lower intensity.
The choices of a power supply and horns/probes are matched to the volume, viscosity and other
parameters of the particular application. Horns/probes are available for both direct and indirect
ultrasonic processing. The frequently asked questions (FAQ) section has more information on
this subject.
Please consult with a product specialist for assistance with selecting a probe for your
application.
Relationship of Amplitude and Wattage
Ultrasonic processing power is measured in watts. Amplitude is a measurement of the
excursion of the tip of the probe (probe is also known as a horn).
Some ultrasonic processors have a wattage display. During operation, the wattage displayed is
the energy required to drive the radiating face of a probe, at that specific amplitude setting
against a specific load, at that particular moment. For example, the unit experiences a higher
load when processing viscous samples than when compared to aqueous samples.
The speed/cruise control on an automobile, can, to a certain extent, be compared to an
ultrasonic processor. The speed/cruise control is designed to ensure that the vehicle maintains
a constant rate of travel. As the terrain elevations change, so do the power requirements. The
cruise control senses these requirements and automatically adjusts the amount of power
delivered by the engine in order to compensate for these ever changing conditions. The greater
the terrain rate of incline and greater the resistance to the movement of the vehicle, the greater
the amount of power that will be delivered by the engine to overcome that resistance and
maintain a constant speed.
The ultrasonic processor was designed to deliver constant amplitude to your liquid sample
regardless of these changes in load (much like the vehicle’s cruise control described above).
As a liquid is processed, the load on the probe will vary due to changes in the liquid sample (i.e.
