Re: LM35 data acquisition system.
- From: John Larkin <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 14 Apr 2009 08:24:12 -0700
On Tue, 14 Apr 2009 07:27:55 -0700 (PDT), Serpent
<microcode.roy@xxxxxxxxx> wrote:
On Apr 14, 6:56 pm, John Larkin
<jjlar...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
The caps in the Sallen-Key filter will charge up to the channelGot it. Will try by introducing a opamp follower (Buffer?) after mux
voltage. When you switch to the next channel, that charge will be shot
back into the 2.2 uF cap of the new channel. That will result in a bit
of channel-channel crosstalk.
You could improve it by adding an opamp follower right after the mux.
if needed.
Do you really need the post-mux filter?I am also not sure. How can I measure or asses noise in this type of
circuits? I have a PC based DSO, oscilloscope. How I can use it to see
the noise presence? is it possible?
Given a 2 uF cap at each mux input, I doubt you need a post-mux
filter. If you do see more noise than you like, just average a bunch
of ADC shots.
This is temperature after all, and LM35s aren't especially accurate
anyhow.
John
.
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- LM35 data acquisition system.
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