Principles Of Operation - Qsonica Sonicator Q700 Operation Manual

4. Principles of Operation

The ultrasonic electronic generator 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 touch screen pad. As you increase the amplitude setting the sonication 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. Smaller tip
diameters (Microtip probes) deliver high intensity sonication 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 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 with a product specialist for assistance with selecting a probe for your application.
Relationship of Amplitude and Wattage
Sonication 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 then
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. viscosity, concentration, temperature,
etc.). As the resistance to the movement of the probe increases (increased load on the probe), additional
power will be delivered by the power supply to ensure that the excursion at the probe tip remains constant.
The displayed wattage readings will vary as the load changes, however the amplitude will remain the same.
The resistance to the movement of the probe determines how much power will be delivered to maintain
amplitude. For example, a ½" probe at 100% amplitude will require approximately 5 watts to operate in air.
The amplitude of this probe is approximately 120um. Insert the probe in water and the wattage reading will
increase to approximately 90 watts. The wattage required to operate the probe will increase as the load
increases but the amplitude remains the same.
Rev. 9-16
7