The wattage used by an ultrasonic homogenizer operating at constant amplitude can vary during processing. This happens because the resistance to the movement of the probe determines how much power needs to be delivered to maintain the desired amplitude. The amount of energy required to maintain a given amplitude will change depending on the viscosity of a liquid sample and, in turn, other factors which may effect viscosity such as temperature.
For example, running a ½” probe at maximum amplitude in air will take approximately 5 watts whereas is takes 90 watts to maintain this amplitude when the probe is inserted in water. (Note that probes should never be in air as it may damage them.) If a liquid with a higher viscosity than water is processed an even higher wattage will be required to maintain the same amplitude.
The wattage it takes to maintain an amplitude will also increase with increasing probe size because it takes more energy to move a larger probe. This is also why the maximum amplitude of a probe decreases with increasing size.
Differently sized ultrasonic homogenizer probes.
The maximum wattage that an ultrasonic homogenizer can deliver will only be used when the resistance of the probe is high enough to need that power to obtain the desired amplitude. It is important to remember that not the total power but the intensity of cavitation shows the effectiveness of sonication. So there is no need to worry if you constantly operate your ultrasonic homogenizer at wattage lower than the maximum power.