Full Bridge Strain gauge for ADA4558

Hi

I am considering ADA4558 to measure load using a load cell with 350ohm bridge resistivity. Datasheet says minimum bridge resistance for ADA4558 should be 2kohm. Does it mean I need a different strain gauge with higher resistance or I can use a 1k resistor on each of signal input pins (or excitation)?

please let me know if I am missing something here. I think 350ohm is very common strain gauge resistance. 

Thanks in advance. 

  • 0
    •  Analog Employees 
    on Oct 19, 2021 11:11 AM

    Hi Hamedhbb,

    Looking at the ADA4558 datasheet, I would think that it's expecting to have the VREG pin drive the reference voltage for the ADC and the bridge sensor, and it can only handle up to 2kohm bridge resistance. Further looking at the spec table's Power Supply section, the supply current can only handle maximum of 7mA, this supply current includes the VREG and the DVDD section of the IC and using a 350ohm bridge resistance will exceed the supply current (I would think the 2kohm minimum bridge resistance is set looking at the VREG pin alone).

    I hope this answers your question Hamedhbb.
    Keep safe.

    Best Regards,
    Dann

  • Thank You. I arrived at the same conclusion. This means I have to either use resistors on excitation lines at the cost of loosing sensitivity or use a buffer connected to VREG to drive the bridge.