The probe should be submerged approximately halfway into the liquid but there are
exceptions. Before processing actual samples, it is recommended to test the probe in
a vessel filled with water to observe the ultrasonic energy and the flow pattern of the
liquid. During this test you can adjust the probe’s depth until you see adequate mixing
and movement of the water.
Power vs. intensity
Power is the measure of the electrical energy that is being delivered to the
converter. It is measured in watts and displayed on the sonicators screen. At the
converter, the electrical energy is transformed into mechanical energy. It does this by
exciting the piezoelectric crystals causing them to move in the longitudinal direction
within the convertor. This change from electrical into mechanical energy causes a
motion that travels through the horn/probe causing the tip to move up and down.
The distance of one movement up and down is called its amplitude. The amplitude is
adjustable. Each probe has a maximum amplitude value. For example, with a 1/8”
diameter probe at setting 100%, the probe will achieve an amplitude of approximately
180μm. At setting 50% the amplitude is approximately 90μm. Note: this is approximate
and not perfectly linear. We measure the amplitude of each probe at 100% and these
values are published in the brochure.
Amplitude and intensity have a direct relationship. If you operate at a low amplitude
setting, you will deliver low intensity sonication. If you operate at a high amplitude set-
ting, you will have high intensity sonication. In order to be able to reproduce results, the
amplitude setting, temperature, viscosity and volume of the sample are all parameters
that need to remain consistent. The amplitude, not the power, is most critical when
trying to reproduce sonication results.
Power has a variable relationship with amplitude/intensity. For example, sonicating
water requires less wattage when compared to a viscous sample (such as oil). While
sonicating both samples at the same amplitude setting the power/wattage will differ
because the viscous sample will require more watts in order to drive the horn. The
viscous sample puts a heavier load on the probe so they system must work harder to
vibrate up and down at the same amplitude setting. The oil may draw double the watts
when operated at the same amplitude as the water sample.
Small fluctuation in the wattage during sonication is normal. Major swings in wattage
(+/- 20 watts) may indicate a problem with the sample, setup or the sonicator itself.
Viscosity Limitations
Viscous solutions and highly concentrated liquids can be difficult to sonicate. If the
liquid is so thick that it cannot be easily poured out of a vessel it is likely too viscous to
be sonicated.
Keeping Samples Cool
Ultrasonic processing causes the liquid temperature to elevate especially with small vol-
umes. Pulsed sonication is always recommended. The addition of an ice bath or recircu-
lating chiller to cool the sample vessel is strongly suggested.