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Multi channel Sigma Delta ADC

Ammar Gandhi76
Prodigy 120 points
Other Parts Discussed in Thread: ADS1232REF, ADS1258, ADS1230
I want to design 16 channel Strain Analyser with 1/4 bridge,1/2 bridge and full bridge applcaition.It uses 120 ohms bridge similar to weigh scale but sensitivity will differ by 1/4,1/2 1nd full i.e. i need thee gain gain of 1,2 and 4 
I need multiplexer at front end to select multiple input good mux with good CMRR and preferably constant current excitation of bridge : can u support with design or application note  
We have good working design with 20 bit sigma delta ADC and 8 bit micro controller and can use any sigma delta adc 
  • 0
    TI__Guru* 92715 points
    Ammar,


    I don't know of any specific strain gauge application notes that cover what you're looking for. However the ADS1232REF is a reference design for a load cell which does cover some of the basics on how things are set up. If you want to read through the user guide, it may provide some information for you:

    www.ti.com/.../sbau120b.pdf

    However, it may be more complicated with 16 channels. One solution may be to use a different ADC with the on-board multiplexer. Of the devices available, I think the ADS1258 might suit your needs. It has a 16-channel multiplexer, with a separate common input. I'd look through the datasheet. This device does have an evaluation module and I'd also look through the user guide for more information:

    www.ti.com/.../sbau126c.pdf

    As for other external multiplexers, I'm not sure I have any recommendations for you. Generally, we do have ADCs with multiplexers, just not with that many channels. I'd ask in another forum if there are any suitable 16 channel multiplexers. I'd try in the Signal Switches Forum here:

    e2e.ti.com/.../170890


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 120 points
    Thanks : I am already using ADS1230 for weigh scale application for qnty of more than 1000 nos per month and good hand on same : We are extending range for other application : ADS1258 should be enough however for better results I want with current source excitation since project is test bench with lot of PC software and there will be distance in wire so to avoid noise I want current source
  • 0 in reply to Ammar Gandhi76
    TI__Guru* 92715 points
    Ammar,
    Ok, I would note that there is no PGA in the ADS1258. If you do decide to try to build your own with the connections from mux out to ADC in, there are limitations with the op-amp because of it's input and output ranges. Also there may be settling time needed because of the op-amp's settling time.
    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 120 points
    I am on way back to India after starting office in Katy-TX:44794: for Indo US business relation so I will reply after three days : However if ADS12158 is not feasible Pl advise other soltion