AVR-Chat

Thanks.  I assume put it in series between the input voltage and the uC ADC
port pin?   Steve

| -----Original Message-----
| From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On
| Behalf Of Roland Jollivet
| Sent: Saturday, February 06, 2010 1:07 AM
| To: AVR-Chat@yahoogroups.com
| Subject: Re: [AVR-Chat] ADC source impedance
| 
| Even if you have a source of 100K, put a small cap, 1uF, at the input
| to the
| ADC. It now becomes very low impedance to the ADC.  (even 100n will be
| fine)
| 
| Time constant is 0.1s, so that's not aproblem. The biggest loss is the
| charge/discharge of the cap if the signal varies a lot.
| 
| Roland
| 
| 
| 
| On 6 February 2010 00:32, Steve Hodge <steve@terrafirma.us> wrote:
| 
| >
| >
| > Thanks a lot for everyone's help. Sounds like I'm good to go. Steve
| >
| >
| > From: AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com> [mailto:
| > AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com>] On Behalf
| > Of Jeff Blaine AC0C
| > Sent: Friday, February 05, 2010 2:12 PM
| >
| > To: AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com>
| > Subject: Re: [AVR-Chat] ADC source impedance
| >
| > Steve,
| >
| > Yes, sorry for the error. 100k. There will be some finite upper range
| to
| > that due to leakage but it's got to me miniscule. But that's the
| general
| > idea. And if you are talking about sampling 1x/sec then the 20K
| mentioned
| > in
| > the other message is not a problem at all. Good luck.
| >
| > Regards/Jeff
| >
| > From: Steve Hodge
| > Sent: Friday, February 05, 2010 2:53 PM
| > To: AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com> <mailto:
| > AVR-Chat%40yahoogroups.com <AVR-Chat%2540yahoogroups.com>>
| > Subject: RE: [AVR-Chat] ADC source impedance
| >
| > Ah, got it. So it sounds like I'm just fine merely doubling it to 20
| Kohms
| > and only sampling once a second. I assume you intended to say "100k
| > equivalent input"? Steve
| >
| > [Non-text portions of this message have been removed]
| >
| >
| >
| 
| 
| [Non-text portions of this message have been removed]
| 
| 
| 
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