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 sonicatorʼs 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 converter. This conversion 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 ½” diameter probe at setting 100%, the probe will achieve an amplitude of approximately 120μm. At setting 50% the amplitude is approximately 60μm. Note this value is approximate and not perfectly linear. Qsonica measures 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 setting, 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 at setting 50% requires less wattage when compared to a viscous sample (such as honey). For both samples the amplitude/intensity is the same but 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 intensity.
Small fluctuations in the wattage display during sonication is normal. Major swings in wattage (+/-20 watts) may indicate a problem with the sample, setup or the sonicator itself.