Re: ADC Help

Jan 27, 2008 3 Replies
B


Hi Guys,


First I would like to thank people for the helpful pushes in what I hope is the right direction.


I could use some help understanding Analog Digital Converters. I've
> read a number of articles which helps somewhat.
>
> I want to measure the peak amplitude and duration of a non repetitive
> signal from a transducer. Ideally as a pair of numbers on a four
> digit LCD display.

The frequency varies very little from 5.5Khz maybe 200 Hz either way. The amplitude peaks just hit 500mv pp and drops to zero over a few cycles. There is no constant repetition of the input. There may be less than a second to a minute or more between bursts.


I assume that a sample & hold will get me the input voltage at the peak. Which leaves me with the time. How do I integrate the input to get a value for this ?


Is it a matter of summing the samples from the output of the ADC ?

Best Regards: Baron.
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J

If you're saying that the peaks are forming a slope and the highest is

500mv pp ? then from what you're saying, it looks like it maybe like a Pulse coded modulation (PCM) type output.. I guess summing would work with a little slope loss on the response but it most likely won't effect your application. I think a vector approach of resolving the response is more appropriate but that depends on what you want to do with it.

But this is kind of strange if you ask me unless it's an event that only takes place now and then..

http://webpages.charter.net/jamie_5"
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P

Only if you can arrange to sample at the time of the peak. A sample-and-hold will sample the signal at whatever time you tell it, and hold that value until you tell it to take another sample.

An active rectifier would get the peak voltage, and hold it for a short time (depending on time constants).

Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca
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B

I see what you mean. Simple op amp and couple of diodes.

Best Regards: Baron.
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