ADC in the millivolt range - please help
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Posts: 46,084
I need to sample a signal that fluctuates from about .5 millivolts to
around 15 millivolts and convert to digital with my stamp. Does
anyone know of an ADC capable in that range. Is there a better way?
Any help appreciated.
around 15 millivolts and convert to digital with my stamp. Does
anyone know of an ADC capable in that range. Is there a better way?
Any help appreciated.
Comments
an op-amp and ADC works great.
Bruce
Original Message
From: sr2500flyer [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=9CXQlncCvCNIsVtRVDRTarHUMUd54YkoKWIg6Qx0-2AaeMecs9ByKu9UTYEO5yUZImErwaYRAap23hrIFX2y]fdarnell@c...[/url
Sent: Tuesday, April 09, 2002 3:56 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] ADC in the millivolt range - please help
I need to sample a signal that fluctuates from about .5 millivolts to
around 15 millivolts and convert to digital with my stamp. Does
anyone know of an ADC capable in that range. Is there a better way?
Any help appreciated.
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around 15 millivolts and convert to digital with my stamp. Does
anyone know of an ADC capable in that range. Is there a better way?
Any help appreciated.
simplest option is an amplifier, one that will bring your signal up
to the range of 1 to 5 volts full scale that an ADC can work with. A
gain factor of x200 would bring the 15 millivolts fs up to 3 volts
fs. For example,
http://www.owlogic.com/usea_dat.htm
is an low-level signal amplifier we sell that offers gain factors
from x2 up to x1500. The circuit inside is straightforward, a two
stage op amp noninverting amplifier. It uses an LT1051 op amp, which
is special due to its very low and stable input offset voltage, <10
microvolts. It is a CMOS CAZ (commutating auto-zero) op-amp. When
you are working with a signal that is significant at 0.5 millivolt,
you have to keep the amplifier errors well below that level.
Another option would be a high resolution ADC. There are 24 bit chips
like the TI ADS124x or the LTC24xx from Linear tech. These can go
right next to the sensor and digitize right down to the microvolt
level. There is Stamp code for them around (SPI serial).
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
>I need to sample a signal that fluctuates from about .5 millivolts to
>around 15 millivolts and convert to digital with my stamp. Does
>anyone know of an ADC capable in that range. Is there a better way?
>Any help appreciated.
level signals directly from a transducer and outputs a serial digital word.
>From: "sr2500flyer" <fdarnell@c...>
>Reply-To: basicstamps@yahoogroups.com
>To: basicstamps@yahoogroups.com
>Subject: [noparse][[/noparse]basicstamps] ADC in the millivolt range - please help
>Date: Wed, 10 Apr 2002 14:33:28 -0000
>
>I need to sample a signal that fluctuates from about .5 millivolts to
>around 15 millivolts and convert to digital with my stamp. Does
>anyone know of an ADC capable in that range. Is there a better way?
>Any help appreciated.
>
>
>
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
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sounds like your amp will work. I'll look into it and the ADC you mention.
Thanks. Thanks to the others that replied as well.
Original Message
From: Tracy Allen [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=zmz3IgUupeCJp46jUFZn0wGOcWmSQZ4BVGQFaG8EGexyiiIYXuDwFS-Snvc_EcIW7a2yoAniH8-o9vBjWw]tracy@e...[/url
Sent: Wednesday, April 10, 2002 11:32 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] ADC in the millivolt range - please help
Is this a slowly varying signal (time scale ~>1 second)? The
simplest option is an amplifier, one that will bring your signal up
to the range of 1 to 5 volts full scale that an ADC can work with. A
gain factor of x200 would bring the 15 millivolts fs up to 3 volts
fs. For example,
http://www.owlogic.com/usea_dat.htm
is an low-level signal amplifier we sell that offers gain factors
from x2 up to x1500. The circuit inside is straightforward, a two
stage op amp noninverting amplifier. It uses an LT1051 op amp, which
is special due to its very low and stable input offset voltage, <10
microvolts. It is a CMOS CAZ (commutating auto-zero) op-amp. When
you are working with a signal that is significant at 0.5 millivolt,
you have to keep the amplifier errors well below that level.
Another option would be a high resolution ADC. There are 24 bit chips
like the TI ADS124x or the LTC24xx from Linear tech. These can go
right next to the sensor and digitize right down to the microvolt
level. There is Stamp code for them around (SPI serial).
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
>I need to sample a signal that fluctuates from about .5 millivolts to
>around 15 millivolts and convert to digital with my stamp. Does
>anyone know of an ADC capable in that range. Is there a better way?
>Any help appreciated.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/