From: "Donovan Parks" Subject: Re: [SeattleRobotics] Understanding Ultrasonic Sensor Datasheet (Help) Attenuation increases with the square of the frequency, and transducer performance decreases. Your alarm may trigger on moths rather than bigger critters. Higher frequency gives you better resolution, and lower minimum velocity for Doppler sonar devices. Ceramics are more robust, and can work as better transmitters than electrostatic kind. Sensor Magazine often has good articles on many different type of sensor systems, articles for technologists and engineers rather than scientists like the AIP journal (which make you pay plenty). For help with your calculations, checkout the article index: http://www.sensorsmag.com/articles/0299/acou0299/index.htm http://www.sensorsmag.com/articles/0399/0399_28/main.shtml http://www.einaudi.cornell.edu/PeaceProgram/acousticweapons.pdf Checkout appendix A.1 on Linear Acoustics for some interesting equations. Scott ******************************************************* Is the American Identity freedom to pursue happiness and profit from the fruit of your own labors, or a servant leased to corporations by corrupt federal government taxing you to your tolerance? How is it IRS permits corporations to evade taxes in offshore 'special purpose entities' (like Enron), yet we peasants are prosecuted? "The strong do as they will, the weak suffer what they must." -Thucydides ******************************************************* -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.