View Full Version : RCtime and cap question

02-08-2007, 01:06 AM
I am doing an rctime routine with a .1uf sm cap and I get good readings sometimes and sometimes they are all wacky.·(25+% different)·Is there a certain type of cap that is preferable?· Or do I need to use a bigger cap.· I am using this in an automobile where the·temp can variate some.

Mike Green
02-08-2007, 01:19 AM
You need to give more information about what you're trying to do and what this circuit is connected to. The capacitor by itself shouldn't provide wacky readings and the temperature shouldn't make that much difference (unless there are rapid, large temperature variations ... not what you're implying).

02-08-2007, 01:22 AM
I just wanted to bound the cap thing off someone. I wanted to eliminate that possibility. It's probably something in my setup.

Paul Baker
02-08-2007, 02:10 AM
Depending of the capacitor used, it's value can change (some super cheap ceramics have +20/-80%), to make sure it's value remains stable over a wide range of temperatures use the CoG variety.

Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
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Parallax, Inc. (http://www.parallax.com)