very impressive, in another article, I also read the ceramic cap is the cause of an issue which makes noise to the ultrasonic circuits. Funny N. Au Group Electronics, New Bedford, MA, http://www.AuElectronics.com ----- Original Message ---- From: Olin Lathrop To: Microcontroller discussion list - Public. Sent: Monday, September 15, 2008 4:42:50 PM Subject: Re: Re [EE] ... A great deal has been made of the'sound' ofcapacitorsbased on dielectric.... comments please...? > The "singing" capacitor problem is old hat. In my first job just a couple of months out of school I was trying to use a National Semiconductor voltage to frequency converter. The circuit was basically working, but the transfer function was all screwy. To track it down I had one of the "desktop controllers" automatically slowly ramp the voltage, measure the frequency, and plot the result. Instead of a straight line, there were large peaks and valleys at regular frequency intervals. I went over the the circuit carefully and had others check it too, but everything seemed correct. Then I called National Semiconductor and eventually spoke to Bob Pease (I hadn't heard of him before, but the older guys were quite impressed I got to talk to him). It didn't take long for Bob to ask what kind of capacitor I was using for one of the critical frequency controlling components. It was a normal ceramic disk. He said maybe the capacitor had some kind of resonance. I had never heard of that before, and frankly was rather skeptical. He asked me to call him back when I resolved the problem or had further questions. It turned out the cap was the problem. With another cap of the same value, everything worked as expected. I called Bob Pease back and told him, and I still remember him saying something like "You're getting quite an education right out of school". He asked me to send him the cap, which I did. Since then I've seen pictures of his office. I expect my plot and the little green ceramic cap taped to it are in one of the many piles at around the mid 1980 level. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist