[beagleboard] Re: BBB Data Aggregation Unit using external ADC

2015-12-03 Thread Chelsea Orefice 
Hi John,

Thanks for getting back to me. I was actually looking at that same ADC 
converter as you posted in your reply. Just looking for some clarification 
on a few things. What type of error would a simple resistor divider 
introduce into the system? I am currently using a cascaded inverting op amp 
system. Not really sure if this will scale the input voltage to a level 
that is compatible with my ADC.

The circuit diagram looks like this: 
[image: Inline image 1]

Looking forward to your reply,
Chels

On Thursday, December 3, 2015 at 5:07:41 PM UTC-5, Chelsea Orefice wrote:
>
> Hi everyone,
>
> I am new to the world of using MCUs and am looking for some assistance on 
> a project that I am currently working on. To sum things up quickly, I am 
> building a data aggregation unit that can convert analog voltage readings 
> to digital values that is to be stored on a USB or SD card. The DAU will 
> collect 3 types of signals, a buffer signal, clipped signal, and a signal 
> passed through a LPF. In the end, the data should be stored as either a 
> MatLab file or .xml file. However, I am facing a few road blocks relating 
> to my design. 
>
> 1.) I need to use a 24 bit ADC for high resolution purposes based on 
> design requirements that were just given to me as I will be collecting data 
> from .1mV to 50V and it has to have a high sample speed rate. Has anyone 
> connected an external ADC to the BBB? If so, what was the brand of your 
> external ADC? How did you connect the ADC to the BBB? (It'd be greatly 
> appreciated to be able to see a design).
>
> 2.) If you have had a similar project to this, was wondering how you went 
> about it. Any advice would be greatly appreciated.
>
>
> As I said before, all of this is very new to me. So thank you for taking 
> the time to help me out. 
>
> Chelsea
>
>
>

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Re: [beagleboard] Re: BBB Data Aggregation Unit using external ADC

2015-12-03 Thread John Syne 


> On Dec 3, 2015, at 3:03 PM, Chelsea Orefice  wrote:
> 
> Hi John,
> 
> Thanks for getting back to me. I was actually looking at that same ADC 
> converter as you posted in your reply. Just looking for some clarification on 
> a few things. What type of error would a simple resistor divider introduce 
> into the system?
You can calculate this from the info provided in the datasheet on page 24 and 
25. The error occurs because of the sample and hold which uses a 9pF capacitor. 
Use T=RC to calculate the time constant. R is the impedance of you input 
circuit. Given the sampling time, you can calculate the measurement error. 

> I am currently using a cascaded inverting op amp system. Not really sure if 
> this will scale the input voltage to a level that is compatible with my ADC.
> 
> The circuit diagram looks like this: 
> 

No image visible. You have to provide a link to an image.

Regards,
John
> 
> Looking forward to your reply,
> Chels
> 
> On Thursday, December 3, 2015 at 5:07:41 PM UTC-5, Chelsea Orefice wrote:
> Hi everyone,
> 
> I am new to the world of using MCUs and am looking for some assistance on a 
> project that I am currently working on. To sum things up quickly, I am 
> building a data aggregation unit that can convert analog voltage readings to 
> digital values that is to be stored on a USB or SD card. The DAU will collect 
> 3 types of signals, a buffer signal, clipped signal, and a signal passed 
> through a LPF. In the end, the data should be stored as either a MatLab file 
> or .xml file. However, I am facing a few road blocks relating to my design. 
> 
> 1.) I need to use a 24 bit ADC for high resolution purposes based on design 
> requirements that were just given to me as I will be collecting data from 
> .1mV to 50V and it has to have a high sample speed rate. Has anyone connected 
> an external ADC to the BBB? If so, what was the brand of your external ADC? 
> How did you connect the ADC to the BBB? (It'd be greatly appreciated to be 
> able to see a design).
> 
> 2.) If you have had a similar project to this, was wondering how you went 
> about it. Any advice would be greatly appreciated.
> 
> 
> As I said before, all of this is very new to me. So thank you for taking the 
> time to help me out. 
> 
> Chelsea
> 
> 
> 
> -- 
> For more options, visit http://beagleboard.org/discuss 
> 
> --- 
> You received this message because you are subscribed to the Google Groups 
> "BeagleBoard" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
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> .
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> .

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