Principles Of Operation - Qsonica Q700 Operation Manual

4. Principles of Operation

The ultrasonic electronic generator transforms AC line pow er 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 dow n the length of the horn/probe w here the tip
longitudinally expands and contracts. The distance the tip travels is dependent on the amplitude
selected by the user through the touch screen pad. As you increase the amplitude setting the
sonication intensity w ill increase w ithin 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. Smaller tip
diameters (Microtip probes) deliver high intensity sonication but the energy is focused w ithin a
small, concentrated area. Larger tip diameters can process larger volumes, but offer low er intensity.
The choices of a generator and horns/probes are matched to the volume, viscosity and other
parameters of the particular application. Horns are available for both direct and indirect sonication.
The Accessories section has more information on this subject.
Please consult w ith a product specialist for assistance w ith selecting a probe for your application.
Relationship of Amplitude and Wattage
Sonication pow er is measured in w atts. Amplitude is a measurement of the excursion of the tip of
the probe (probe is also know n as a horn).
Some ultrasonic processors have a w attage display. During operation, the w attage 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 w hen
processing viscous samples then w hen 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 pow er requirements. The cruise control
senses these requirements, and automatically adjusts the amount of pow er 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 pow er that
w ill be delivered by the engine to overcome that resistance and maintain a constant speed.
The ultrasonic processor w as 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 w ill vary due to changes in the liquid sample (i.e.
viscosity, concentration, temperature, etc.). As the resistance to the movement of the probe
increases (increased load on the probe), additional pow er w ill be delivered by the pow er supply to
ensure that the excursion at the probe tip remains constant. The displayed w attage readings w ill
vary as the load changes, how ever the amplitude w ill remain the same.
The resistance to the movement of the probe determines how much pow er w ill be delivered to
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