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ADS1248

surender kumar
Prodigy 120 points

Thank you very much for your timely response. Sorry that i had uploaded a old schematic before. The present circuit schematic has been uploaded now in which i hav been facing the fluctuation issues . And the VREFCOM has been connected to AGND in this schematic as suggested but problem still persists .

The problem is that if the ic is sampled at 20 sps a stable reading is obtained in the output, But when the sampling is done at 80 sps , there is a huge fluctuation in the output count obtained from the Ic.

The reason for going for a higher sps is the conversion time. Sampling @20sps with 6 ADS1248 IC's for reading 12channels takes a time of ~3sec for convertion. So for bringing down the conversion time, we are planning to sample @ 80 sps which may decrease the conversion time to ~1.2 seconds. sampling @80sps is also reading the proper value , but the fluctuation has been the issue.

Any help will be appreciated. Thank you in advance. .

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    TI__Guru* 94285 points
    Surender,


    First, when you want to respond to the same topic, just reply to the original post so that we can keep the line of questions and answers in the same place. Let's use the original post here, and reply to that:

    e2e.ti.com/.../426634

    You refer to my second post about the unconnected VREFCOM, but you didn't say anything about my first post. Go to the above link and read through my first response.

    Is it possible that what you are seeing is line cycle noise? In addition to my recommendations, you may want to try to read the data at 1kSPS and see if you can clearly see 50Hz noise.


    Joseph Wu