CN0326: Isolated Low Power pH Monitor with Temperature Compensation

For questions or comments on CN0326, please reply below

  • Dear Sir,

    We are excited to see pH monitor with Temperature compensation application and would like to know more on this as below

    1) This has reference to the configuration available in the evaluation kit Ref EVAL-CN0326-PMDZ Board

    2) We understand from your Description for pH application following are important

         ....Guarding, shielding, high insulation resistance standoffs, and other  such standard picoamp methods must be used to minimize leakage at the  high impedance input of the AD8603 buffer...

    3) But in the Evaluation Board we do not see any High Insulation resistance StandOff , nor any shield available?. We  see in EVAL-CN0326-PMDZ Board, AD8603 IC pin 3 is directly soldered to PCB and pH probe input is connected to this point. We wish to know wheather PCB impedance is acceptable by doing so for this application?

    4) We are unable to find uC firmware C source code for this pH application for this kit? Can we get the same?

    5) What modification need to be done for pt 100 RTD?




    •  Analog Employees 
    on Mar 17, 2014 6:06 PM over 6 years ago

    Hi Gowrishankar,

    Below are the answers to your inquires.

    3. High insulation resistance standoff and shielding will vary depending on the environment where the kit will be used.  It is highly recommended to use High insulation resistance standoff if this kit will be integrated or will be surrounded with high voltage circuits.  And a proper shielding should be applied for applications where RF noise is highly observed in the area.

    For detail discussion about shielding and guarding, please refer to this link.

    AD8603 can be directly connected to the input of the pH probe as long as a proper guarding/static shielding is observed.  Due to the low frequency operating range of the circuit (<500Hz), the performance of the board would not be highly affected by the PCB impedance. It is highly affected by the input bias current of the buffer due to the high input impedance of the  pH probe sensor.  The circuit note for this kit gives us the overall performance of the board.  It includes the system noise and offset generated base from the PCB design of the kit.

    4.  The software use for this kit is a labview and uses System Demonstration Platform (EVAL-SDP-CB1Z)

    and SDP PMOD Interposer Board (SDP-PMD-IB1Z) to evaluate the kit using the evaluation software included in the kit. You can evaluate this kit using other microcontroller  via its pmod pin (pin J2) which makes this board more flexible to use.

    5.  The RTD resistance value of the included evaluation software can be varied according to the application needed.  The RTD should be connected properly in the kit since this creates current path to the 5kohms resistor (R2) that generates the voltage reference to the ADC.



  • Dear Erbe,

    Thank you for your clarifications. we are unable to find SOURCE CODE of pH application software. Is it possible to share the same? our idea is to use this EVAL-CN0326-PMDZ module with our micro controller + display as a standalone pH meter. therefore we require pH processing algorithm for this module



    •  Analog Employees 
    on Mar 27, 2014 6:22 PM over 6 years ago

    Hi Elico,

    Unfortunately the evaluation software was designed in LabVIEW, so we won't be able to provide processor code specific to this application.

    Here are some AD7793 driver links:

    AD7793 - Microcontroller No-OS Driver    [Analog Devices Wiki]

    AD7793 IIO Low Power Sigma-Delta ADC Linux Driver    [Analog Devices Wiki]

    You might be more interested in this direct download:


    •  Analog Employees 
    on Mar 27, 2014 8:31 PM over 6 years ago

    I think you are looking for:

    It's not specific for that Pmod - but is for the same converter.