The WATTS reading displayed on the screen is the amount of electrical energy the ultrasonic generator delivers to the converter.
NOTE: The greater the resistance to the movement of the probe, the greater the amount of power that will be delivered to the probe. As a liquid is being processed, its viscosity and chemical characteristics will change causing the power readings to fluctuate.
How to calculate the power that is being delivered to a sample:
Turn on the equipment
Set the amplitude as required
With the probe in air, not immersed in a sample, record the amount of watts displayed on the power monitor
Without changing the amplitude setting, immerse the probe into the sample and record the amount of watts displayed on the power monitor
The difference in power readings between step 3 and 4, is the amount of power being delivered to the sample in watts
To obtain the power density in watts/cm², divide the number of watts obtained in step 5 by the area of the probe tip.
Area = (diameter/2)² x π or π r²
Area using a 3mm probe: 3mm/10 = .3cm = .15cm radius
.15²cm X 3.142 (π) = .0707cm²
Now divide the number of watts by the area of the probe.
Using 1 watt as an example, the power density would be 1/.0707 = 14 watt/cm²
NOTE: The intensity is expressed as watts per surface area. (watts/cm²)