Qsonica Sonicator Q700 Operation Manual - page 9
Rev. 6-12
9
4. Principles of Operation
The ult rasonic elect ronic generat or t ransforms AC line pow er to a 20 KHz signal t hat drives a
piezoelect ric converter/t ransducer. This elect rical signal is converted by the t ransducer t o a
mechanical vibrat ion due to t he charact erist ics of the internal piezoelect ric cryst als.
The vibrat ion is amplif ied and t ransmit t ed dow n the lengt h of t he horn/probe w here t he t ip
longit udinally expands and cont ract s. The dist ance the t ip t ravels is dependent on t he amplit ude
selected by the user through the t ouch screen pad. As you increase t he amplit ude set t ing t he
sonicat ion intensit y w ill increase w it hin your sample.
In liquid, t he rapid vibrat ion of t he t ip causes cavitation, t he format ion and violent collapse of
microscopic bubbles. The collapse of t housands of cavitat ion bubbles releases t remendous energy
in t he cavitat ion f ield. The erosion and shock ef fect of t he collapse of the cavit at ion bubble is t he
primary mechanism of f luid processing.
The probe t ip diameter dict at es t he amount of sample t hat can be ef fect ively processed. Smaller t ip
diameters (Microt ip probes) deliver high int ensit y sonicat ion but t he energy is f ocused w ithin a
small, concent rat ed area. Larger t ip diameters can process larger volumes, but of f er low er intensit y.
The choices of a generat or and horns/probes are mat ched t o t he volume, viscosit y and ot her
paramet ers of t he part icular applicat ion. Horns are available f or both direct and indirect sonicat ion.
The Accessories sect ion has more inf ormation on this subject.
Please consult w it h a product specialist for assist ance w ith select ing a probe f or your applicat ion.
Relationship of Amplitude and Wattage
Sonicat ion pow er is measured in w at t s. Amplit ude is a measurement of t he excursion of t he t ip of
t he probe (probe is also know n as a horn).
Some ult rasonic processors have a w at t age display. During operat ion, t he w at tage displayed is t he
energy required to drive the radiat ing face of a probe, at that specif ic amplit ude sett ing against a
specif ic load, at that part icular moment . For example, the unit experiences a higher load w hen
processing viscous samples t hen w hen compared to aqueous samples.
The speed /cruise cont rol on an aut omobile, can, t o a cert ain ext ent , be compared t o an Ult rasonic
Processor. The speed/cruise cont rol is designed t o ensure t hat the vehicle maintains a const ant rat e
of t ravel. As t he terrain elevat ions change, so do t he pow er requirement s. The cruise cont rol
senses t hese requirements, and aut omat ically adjust s t he amount of pow er delivered by t he engine
in order to compensate for t hese ever changing condit ions. The greater the terrain rat e of incline
and great er t he resist ance t o t he movement of t he vehicle, t he greater the amount of pow er that
w ill be delivered by t he engine t o overcome t hat resist ance and maintain a const ant speed.
The ult rasonic processor w as designed t o deliver const ant amplit ude, to your liquid sample,
regardless of these changes in load (m
uch like the vehicle’ s cruise control described above). As a
liquid is processed, t he load on t he probe w ill vary due t o changes in t he liquid sample (i.e.
viscosit y, concent rat ion, temperat ure, et c.). As t he resist ance to the movement of t he probe
increases (increased load on the probe), addit ional pow er w ill be delivered by t he pow er supply t o
ensure t hat the excursion at the probe t ip remains const ant . The displayed w at t age readings w ill
vary as t he load changes, how ever t he amplit ude w ill remain t he same.
The resist ance t o t he movement of t he probe determines how much pow er w ill be delivered t o