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?
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.
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
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:
You might be more interested in this direct download:
I think you are looking for:
It's not specific for that Pmod - but is for the same converter.
Under section 3.3 found form the link below is a good reference to implement in C code the equations for pH calibration.
I am working with "EVAL-CN0326-PMDZ REV.A" evaluation board for pH measuring application. While searching for CN0326 Evaluation LabWIEW Software, i found that there are three different version of the software could you please what difference is there between each version. Is it possible to get source code for latest version for studying the working flow, CAL and pH measurement math function.
Thank you for having an interest with CN0326 Evla Board.
you should use the latest version 2.0.0 found for your study.
the source code for CN0326 Evaluation Software will be sent over to your email address.
The software we develop for CN0326 Evaluation board is for evaluation purposes only.
Attached is a source code of the latest Evaluation Software V2.0.0
Note: We gladly give out the source code of the software to expidite the user's development tiem but we'e not steup to support any modification to the code.
Currently we want to use the CN0326 chip for integrating pH and temperature indications in a controller, using a regular pH electrode and a pT100 temperature sensor. For a while I am testing the chip for precise temperature indications (pH indications work quite fine), but here a problem is occuring in terms of precision. I have been testing some configurations for the AD7793 registers but I'm not sure which setting is the best.
Currently the configuration of the AD7793 is the following:
IOUT1 current = 1 mA
Biasing= Bias AIN1
Gain = 2
Reference voltage = external reference
Channel = AIN2
This configuration results in a standard deviation of 0.16 Degrees celsius (N=70). Is this the expected precision for a pT100, do I need a different configuration?
thank you for considering CN0326 as part of your system.
i currently not seeing any issue with the configuration you write in the ADC register.
The issue with the precision would somehow be related to the precision of the DAC current source of AD7793, which shows a 5% initial tolerance at 25degC. But from the result you have just shown, a deviation of 0.16degC is still acceptable. If the source of error is correct, we can compute for the error introduce by the current source which gives us a result of +/-0.5616uA or +/-0.05%.
Please let me know if there is anything else you want to verify.