ADC for strain gauge measurement

Discussion in 'General Electronics Chat' started by aamirali, Aug 11, 2014.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    I have strain gauge of 1K, 50000 microstarin , & Gf = 2, so for 1 microstarin change in resistance is 2milliohm.
    I am using external reference created by IDAC current on reference pins


    1. Currently i am using ADS1248, by directly passing 50uA through strain gauge without any bridge, with PGA = 32

    So ideally at 1000ohm i.e 0 strain, voltage is 50000 microvolt

    & 1 microstain voltage is 50000.1 microvolt. So change of 100nV.

    Will ADS1248 will be able to sense such small changes?

    2. If not, is there any ADC which can do this job better

    3. Is is correct method to directly send current across strain gauge & measure change in resistance rather than brigde
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,693
    2,762
    You need to study the datasheet. The input referred RMS noise at a gain of 32 varies between 70nV at a sample rate of 5 per second to 1.36 uV at 2000 samples per second.

    If you choose the slowest sample rate, you will have, 20.9 effective bits of resolution, or 1 in 1,956,712.

    You can also use a faster sample rate, but use a rolling average to eliminate noise.

    Keep in mind, though, that this is the noise performance of the A/D itself, which is quite good. I don't know the level of your experience, but I think it will be difficult to reduce the noise of your input signal to less than that of the A/D.
     
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