A/D Conversion of an AC Signal
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Posts: 46,084
Hi Everyone:
How would I go about converting an AC signal into an A/D converter
without
having to use external circuitry to shift the zero volt level of the
sine
wave? I was thinking of trying to put a +/-2.5V split supply on an A/D
converter so that the 0V signal would correspond to a bit value of
50%, -2.5V corresponds to 0%, and 2.5V corresponds to 100%. Can a
split
supply arrangement be done without smoking a LTC1298 A/D chip? The
specs for
the IC do not shed any light on this and give the impression that you
can
only put on 5VDC. Is there another A/D chip out there specifically
designed
for this type of conversion? The intent is to continuously sample and
copy a
full sine wave into a data register, which can then be mathematically
manipulated. I am also looking for fairly good frequency resolution
(up to
50 kHz) so if my only alternative is to use a conditioning op amp
circuit to
shift the 0V level to 2.5V, it would need to be able to handle
frequencies
up to this level.
Any help or insights would be appreciated.
Thanks and regards,
Gerry Shand
gshand@h...
How would I go about converting an AC signal into an A/D converter
without
having to use external circuitry to shift the zero volt level of the
sine
wave? I was thinking of trying to put a +/-2.5V split supply on an A/D
converter so that the 0V signal would correspond to a bit value of
50%, -2.5V corresponds to 0%, and 2.5V corresponds to 100%. Can a
split
supply arrangement be done without smoking a LTC1298 A/D chip? The
specs for
the IC do not shed any light on this and give the impression that you
can
only put on 5VDC. Is there another A/D chip out there specifically
designed
for this type of conversion? The intent is to continuously sample and
copy a
full sine wave into a data register, which can then be mathematically
manipulated. I am also looking for fairly good frequency resolution
(up to
50 kHz) so if my only alternative is to use a conditioning op amp
circuit to
shift the 0V level to 2.5V, it would need to be able to handle
frequencies
up to this level.
Any help or insights would be appreciated.
Thanks and regards,
Gerry Shand
gshand@h...
Comments
I haven't actually tried this with a 1286 or 1298, but since the max Vcc is
12V, you should be able to offset Gnd to -2.5V. I would think that you would
be dealing with a 2.5V data output however. The 1298 shares Vcc with Vref,
so it's probably not the right choice. The 1298 really should be used with
up to 5.5V Vcc (I think) so I wouldn't try this for anything serious.
Have you checked pgs 16 & 17 of the data sheet, which includes notes on
converting sinusoidal input?
Chris
>
> How would I go about converting an AC signal into an A/D converter
> without
> having to use external circuitry to shift the zero volt level of the
> sine
> wave? I was thinking of trying to put a +/-2.5V split supply on an A/D
> converter so that the 0V signal would correspond to a bit value of
> 50%, -2.5V corresponds to 0%, and 2.5V corresponds to 100%. Can a
> split
> supply arrangement be done without smoking a LTC1298 A/D chip? The
> specs for
> the IC do not shed any light on this and give the impression that you
> can
> only put on 5VDC. Is there another A/D chip out there specifically
> designed
> for this type of conversion? The intent is to continuously sample and
> copy a
> full sine wave into a data register, which can then be mathematically
> manipulated. I am also looking for fairly good frequency resolution
> (up to
> 50 kHz) so if my only alternative is to use a conditioning op amp
> circuit to
> shift the 0V level to 2.5V, it would need to be able to handle
> frequencies
> up to this level.
>
> Any help or insights would be appreciated.
>
> Thanks and regards,
>
> Gerry Shand
> gshand@h...
>
MICROCHIP / TELECOM TC3401 16 BIT ADC
Original Message
From: "ronlizus" <ronlizus@y...>
To: <basicstamps@yahoogroups.com>
Sent: March 12, 2002 8:05 AM
Subject: [noparse][[/noparse]basicstamps] A/D Conversion of an AC Signal
Hi Everyone:
How would I go about converting an AC signal into an A/D
converter
without
having to use external circuitry to shift the zero volt level of
the
sine
wave? I was thinking of trying to put a +/-2.5V split supply on
an A/D
converter so that the 0V signal would correspond to a bit value
of
50%, -2.5V corresponds to 0%, and 2.5V corresponds to 100%. Can a
split
supply arrangement be done without smoking a LTC1298 A/D chip?
The
specs for
the IC do not shed any light on this and give the impression that
you
can
only put on 5VDC. Is there another A/D chip out there
specifically
designed
for this type of conversion? The intent is to continuously sample
and
copy a
full sine wave into a data register, which can then be
mathematically
manipulated. I am also looking for fairly good frequency
resolution
(up to
50 kHz) so if my only alternative is to use a conditioning op amp
circuit to
shift the 0V level to 2.5V, it would need to be able to handle
frequencies
up to this level.
Any help or insights would be appreciated.
Thanks and regards,
Gerry Shand
gshand@h...
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