My recent blog, Are Ultrasonic Power Ratings Real?, prompted a response from my friend and colleague William Puskas. Some of you may know Bill as the “Father of Sweep” as he was the first to implement frequency sweeping technology in ultrasonic cleaning equipment decades ago. He is also the author of a significant number of patents in the field of ultrasonic technology.
The issue of watts, power, etc. in ultrasonic systems is nothing new to Bill as he has been fighting this battle for years along with the rest of us who believe that there must be a better way to quantify ultrasonic capability. Now if only we could find it and all agree!
OK, so here we go – – Bill, it’s all yours.
Ultrasonic Power — Terminology and Applications
Power, the rate of energy delivery, is sometimes described as “average power”, “RMS power”, “peak power”, “instantaneous power”, “real power” or simply “power”. “Average power”, “RMS power”, “real power” and “power” are alternative names for the same quantity. “Instantaneous power” is the rate of energy delivery at a specified point in time. “Peak power” is the maximum value of “instantaneous power”. The quantitative terms used in this discussion will be limited to average power and peak power. When referring to both, the word power will be used.
For ultrasonic systems, average power, peak power and the ratio of peak power divided by average power are the most useful electrical power parameters. Unfortunately, sales literature often quotes only one power number and it is not always clear which parameter it is. Talk to an electrical engineer at the company to get accurate power numbers.
Assuming you are comparing modern equipment with generator efficiencies greater than 90% and piezoelectric transducers with sufficient surface area to couple the power into the cleaning liquid, average power is the best parameter to use. Warning, overdriven transducers will result in high average power and lower system cost, but power is wasted in surface cavitation.
The ratio of peak power to average power is useful when the application is known. A low ratio (1.1 to 4) is best for precision cleaning applications. A higher ratio is best for industrial cleaning, especially in adverse conditions such as contaminated, gaseous or turbulent cleaning chemistries.
Low peak power to average power ratios are produced by generators with high duty cycle outputs and transducers with relatively flat impedance characteristics. High ratios are produced by generators that output full power at a low duty cycle or by transducers with sharp impedance curves. Low duty cycle generators are the best way to achieve a high ratio because sharp transducer characteristics reduce the positive effects of sweeping frequency.
William L. Puskas – – November 19, 2019
Thanks for the insight, Bill. The time has come for this topic to be addressed. Anyone else who is interested is welcome to chime in as always. Just use the “comments” or email directly to me at email@example.com.
– JF –