Change excitation voltage to 10 mV in EVAL-AD5933EBZ

Hello,

I am trying to use EVAL-AD5933EBZ for corrosion tests. For this I need to use an excitation voltage of 10 mV or 20 mV. Do you have any tips on how to do this? The board has a minimum 200 mV from the factory.

Thanks for your time

Best regards,

Rafael!

  • Unfortunately there seem to be no easy or elegant way of doing so without cutting some traces on the EVAL board and adding some dangling components. If we refer to the diagram in the UG-364, p.23, Fig. 31. the most straightforward modification would be disconnect the C7 right pin from the line it shown connected to and adding a resistive R-R divider between the LK2-T8-VOUT and the ground: say 19k to VOUT and 1k to the ground and reconnecting the right C7 pin to the point between the two resistors. This would divide the output voltage by 20, which at 200 mV setting wold give the desired 10 mV excitation.

    If mutilating the board is not acceptable, an OPAMP with two resistors could be mounted in breadborging area of the demo board: OPAMP V+ connected to VDD, V- to GND, In+ connected to the point between R2 and R1,  A resistor of, say 1k is connected between the OPAMP Vout and In- and a resistor of, say 20k connected between In- and the bottom pin of Z. This would make the OPAMP into a 1/20 attenuator. Atter this modification Z should be connected to the new OPAMP's  Vout.

    The EVAL board references its signals with respect to Vdd/2, hopefully you will not run into additional issues with your experimental cell as it may require real ground etc.

  • Hi Snorlax

        Thank you very much for your help! I'll try the use of breadbord.

    Best regards,

    Rafael