Re: Texas TMS1232 Delta Sigma converters

On Tue, 01 Nov 2005 10:00:49 +1000, Adrian Jansen <adrian@xxxxxxxxx>
wrote:

>Hi All,
>
>Just got some samples of these very nice Delta-Sigma A/D converters,
>complete with built-in amplifiers for a new project.
>
>A quick bench lash-up hooked to an AVR processor development system
>shows promising results when used direct with a gain of 64 ( I have a
>bridge output type sensor with a full scale 25 mV output ). I didnt
>expect too good a noise result on just a lash-up, and in fact only
>achieved about 16-17 bit samples above the noise. But I need at least
>18 bits, and 19 would be nice at 10 samples/sec, before averaging.
>
>Anyone played with these ? Any good tips on layout and input filtering
>to remove as much noise as possible ?

What's a TMS1232? I can't find it.

Make sure you're not picking up 50/60 Hz line noise, and that your
voltage reference isn't noisy. 19 bits it thin air.

If you can't reduce the sample rate, all you could do is add some
analog filtering ahead of the ADC, but that equivalently slows it
down, so you can't filter too hard.

Is this a weighing application? If so, vibration will be a serious
problem, and the only fix is lower sampling rates or more averaging,
which amounts to pretty much the same thing.

John

.

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