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From: Spehro Pefhany
Subject: Re: 10 bits dual slope coverter
X-Newsreader: Forte Agent 1.92/32.572
Date: Thu, 12 Dec 2002 02:52:45 GMT
NNTP-Posting-Date: Wed, 11 Dec 2002 21:52:45 EST
On Thu, 12 Dec 2002 10:42:38 +0800, the renowned "Reala" <-> wrote:
>I am doing a test for 10 bits resolution A/D convertor IC.
>The external component of ADC is very simple.
>one R reference (reference resister), Cext (capacitor) and Rx (resister
>To measure the Rx, I write a testing program read 1000 output data of ADC
>within 10 second.
>the result is that:
>Value No. of count
>The output is 759-767. delta:767-759=8
>I expected that the delta (max - min) is 1 to 2....because this is under the
>same testing condition.
>Do you have any idea about my result? Is this a normal result for other ADC
>how can i improvement this?
Don't know where the noise is coming from. You could also have some
kind of jitter issue in generating/measuring the periods. You are not
doing something silly like using a crummy ceramic capacitor instead of
a proper film cap for the integrator? You're not trying to convert
tiny voltages like 10mV directly are you? How about AC hum on the
signal? You do have to be a bit careful when breadboarding this
type of circuit.
>How can i address the accuracy of this IC?
>or the error is introduced by external components or voltage supply?
>Any one do the similar test before? What is the result?
7106/7 converters are stable to within a fraction of a count,
when used with recommended parts and not too low a reference voltage.
At only 750 counts, they would be dead steady. It's not so difficult
to get usable 15 bit readings, your 9-10 bit reading should be a
piece of cake.
"it's the network..." "The Journey is the reward"
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