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ADS1246 for Strain gauge bridge

Luis Filipe Rossi1
Prodigy 250 points
Other Parts Discussed in Thread: ADS1246, ADS1248, ADS1220

I posted this in the wrong Forum  with my other account (HERE) . Sorry for that

Hello, 

I need to implement a Full Strain Gauge Bridge sensor with minimum BW of 40Hz. I am considering using the ADS1246 with a 5V Analog Supply  generated by a TPS7A49 and reference in ratiometric mode.  Is there any pitfall i should take in consideration. As the ADS1246 is suposed to be used in temperature sensors i might be missing something. The best solution would be ADS1230 but the cornet frequency of 11hz is too low. I will probably be using some CM0 microcontroller with 3.3V power. Finally, any advice on using or not a common mode input filter, or maybe just a capacitor between both inputs (as recommended in the slyp163.pdf presentation)

Regards,).

  • 0
    TI__Guru* 97585 points
    Luis,


    There shouldn't be anything wrong with using the ADS1246 for a strain gauge measurement. I know of a few applications that use the ADS1248 family for that application.

    There are a couple of things to note in using this device. The reference voltage input only goes up to about 4V using a 5V supply (which might limit the source of the bridge). Another thing is that you need to make sure that the inputs are within the common mode input range. When PGA=1 and AVDD=5V, make sure the input is between the GND+0.1V, and AVDD-0.1V. When the PGA is on, there are additional range restrictions because the input and output common mode of the PGA needs to be met.

    If you want to consider it, the ADS1220 might be a better choice. The reference voltage goes all the way to AVDD. While the PGA will have similar input range restrictions, there is a slightly better input range. In particular, When the gain is 1, 2, and 4, the gain is implemented without the PGA and has a much better input range.


    Joseph Wu
  • 0
    TI__Guru* 97585 points
    Luis,


    Also, we also recommend modest filtering with common-mode and differential capacitors.

    If you look at the ADS1248EVM, there are input filters on the board and you can use the values shown in the schematic. They should work as basic input filtering.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 250 points
    Joseph, Thank you for your replay and answer. I am strongly considering the ADS1220 for my design. The only point that bothers me is the lack of calibration. Am i not going to have a long time problem of drift with no calibration?
  • 0 in reply to Luis Filipe Rossi1
    Prodigy 250 points
    Never mind. Just noticed i can do that manually storing the offset value in the microcontroller.