Hi,
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I repost this because someone mailed me that it showed up strange in his =
mail, so excuse me if you get it 2 times. So, here's my original message:
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I want to make an circuit to measure angles, both for myself, just to see=
 if I can and also because I'll probably be able to use it in an assignme=
nt for university later this year.
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Since I want to be able to measure up to 1mV precise and the system will =
be working on 5V, I need at least 13 bit of resolution (right?). To measu=
re angles I'll be using an accelerometer, a dual-axis one, so that I can =
measure any angle from 0 to 360 degrees with good accuracy (the accuracy =
using only a single axis one isn't that good anymore once you reach +- 60=
 degrees). So I need 2 A/D channels. The maximum output of the accelerome=
ter shouldn't be higher than 4V.
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Also, I'd like I=B2C for data transfer, since the sensor needs to be as s=
mall as possible and thus I'll have a separate board for a =B5C and possi=
bly other circuitry. The only things on the sensor PCB will be the accele=
rometer, an LDO linear voltage regulator and the A/D converter(s). So, be=
cause of that I can't have a 48LCC A/D converter on the board, it would m=
ake it way too big. (Everything will be SMD of course.)
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I've been spending the last 2 hours searching sites of big manufacturers =
for that kind of A/D converter and the only good ones I've found are the =
Maxim MAX1069 (14-bits) and MAX1169 (16-bits), but they've only got 1 cha=
nnel. There's also the Maxim DS2450, which is 16-bits, but starting at on=
ly 9-bits, the accuracy is lower than the resolution. I also found the TI=
 ADS1112, which is very nice, being in a SOP6 package and all, but it onl=
y supports input voltages up to 2.046 (or something like that).
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So, I was wondering if anyone knew of any small (16SOIC is not small), at=
 least 13-bits, preferably 2 channels (but 1 is OK if it's a SOP6 package=
 for example), I=B2C (or 1-wire, but rather not) A/D converter?
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Oh, sample rate isn't very important, as long as I can aqcuire more than =
60 samples/second that should be fine, I'm measuring tilt after all, so c=
hanges pretty slow.
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Or are my demands just too high?
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Thanks, Anthony Van Herrewege




Website: http://members.lycos.nl/anthonyvh

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