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Sunny Guest
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Posted: Thu May 08, 2008 2:29 pm |
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Thanks again. I'll follow your advice and do some test with another AD pin to try out the code first. Will let you know how it goes.
Best Regards! |
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jfarkas
Joined: 07 Dec 2006 Posts: 4 Location: Croatia
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Posted: Thu May 08, 2008 3:04 pm |
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The maximum recommended impedance for analog sources is 2.5 kΩ.
From datasheet |
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Guest
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Posted: Fri May 09, 2008 11:42 am |
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Thanks for the comment, jfarkas.
PCM Programmer, I removed all the connections to the AN0 pin, just used a 100ohm pot to adjust the voltage. However it's still the same thing (except that now it's 1.3 times instead of 1.25 times) ! I really don't know what's wrong there.
Then I used another bare board to build up a circuit just contains the PIC and the pot, it works.
I'm not going to spend more time on this one for now. Luckily I don't need the whole 5V range, so I'll just scale it in the code to have a "proper" pressure value.
Thanks again for your help! |
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Ttelmah Guest
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Posted: Fri May 09, 2008 2:52 pm |
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I'd be looking very carefully at how stable, and well decoupled the supply rail is. All the calculations you have done, are based on the chip having _exactly_ 5v at the supply pin....
Best Wishes |
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Sunny Guest
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Posted: Mon May 12, 2008 12:45 pm |
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Ttelmah wrote: | I'd be looking very carefully at how stable, and well decoupled the supply rail is. All the calculations you have done, are based on the chip having _exactly_ 5v at the supply pin....
Best Wishes |
Yes that's a good hint. I checked the VCC and now the problem is solved!
Thank you very much! |
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