Power versus Amplitude versus Joules - for shearing via sonication (May/06/2011 )

Hi all,

Could someone with sonication expertise explain the differences between power output, amplitude, and joules when shearing DNA by sonication? I noticed some devices recommend settings by power (watts) whereas others recommend amplitude. And many protocols mention joules. What is better or more appropriate in terms of reproducibility and precision? Btw, I am using an Episonic if that helps, which has all three types of sonication measurement displayed on the screen, hence my question.

A Watt is a Joule per second. Amplitude is the size of the wave produced and will be related to the power of the device somehow, but I am not a physicist, and it should be easy enough to google.

Note: Watts and Joules are named after people so should be capitalized (just in case you didn't know and you need them for your final write up).