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ADS1231REF: ADS1231REF

Shekhar Tilve1
Prodigy 120 points
Part Number: ADS1231REF
Other Parts Discussed in Thread: ADS1231,

Hi .   We are interfacing a strain gauge to this evaluation board .  We are unable to measure at lower input ranges in uv range . What is the minimum resolution this device can support in terms of uV  for  3 Volt VCc

Kindly share link of any application note for interface with strain gauge

  • 0
    TI__Guru** 113765 points

    Hi Shekhar,

    The ADS1231 is designed specifically for sensors that are in a Wheatstone bridge type configuration.  A strain gauge element that is part of a Wheatstone bridge configuration is called a load cell.  A load cell can be in 1/4, 1/2 and full bridge configurations.

    As I have no information as to the specifics of the strain gauge you are using nor what type of strain is being measured it is difficult for me to suggest an appropriate way to connect this to the ADS1231.  One method might be to create your own bridge where the strain gauge is one of the leg elements.  In general you cannot just connect a strain gauge element to the ADS1231 directly as you must meet the common-mode input requirements for the PGA.  

    National Instruments has a white paper that can be viewed online regarding the topic of Measuring Strain with Strain Gages:

    https://www.ni.com/en-us/innovations/white-papers/07/measuring-strain-with-strain-gages.html


    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 120 points

    HI ,

    We are interfacing the strain gauge with an wheatstone bridge configuration. The output of strain gauge arm is provided as input to this IC . We are unable to measure the lower range values ,hence the query of minimum input the IC can receive

  • 0 in reply to Shekhar Tilve1
    TI__Guru** 113765 points

    Hi Shekhar,

    Unfortunately you have given me very little useful information.  As to the performance of the ADS1231, this is given in the datasheet on page 6 in Table 1.  The best noise performance is at 10 sps, and noise-free bits or peak-to-peak noise is the most useful information for you to determine performance.  For a 3V operation, the best case scenario is typically 199.2nV.  This means that you cannot resolve less than this voltage.  So this means that you should be able to measure a uV or less.  As to the ADS1231REF, this board is designed to run from 5V AVDD and not 3V.  So have you modified the board, or are you just applying an external voltage to the reference?  How have you connected the bridge to the ADS1231REF?  Have you removed the shorting jumpers J7 and J8?  Can you send me pictures of your setup and a detailed description of the strain gauge and resistors used in the bridge?

    All that said, this is what the ADS1231 can potentially achieve, but external noise sources can make this measurement much worse.  Cabling from your bridge circuit to the ADS1231REF can act as an antenna and can pick up noise sources such as EMI/RFI.

    One further piece of information I will share regarding your bridge circuit.  If your bridge elements are such that the input can deviate too close to AVDD or AGND, then you will be outside of the input range of the PGA.  Also, a balanced bridge should have a 0 differential voltage at the outputs centered about 1/2 of the excitation supply.  If there is a mismatch in devices used, you will see and offset and this must be accounted for in your measurement.  Also, with a 3V excitation/reference the maximum input range is +/- 0.5*3/128 or +/ 11.7mV.

    Best regards,

    Bob B