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ADS124S08EVM: Question Regarding How to use GUI

Shinichi Inoue
Guru 21566 points
Part Number: ADS124S08EVM
Other Parts Discussed in Thread: ADS1220EVM, ADS124S08

Tool/software:

Dear Specialists,

My customer is testing ADS124S08EVM and has questions.

I would be grateful if you could advise.

---

I have obtained the ADS124S08EVM and am evaluating, I have some questions.

Could you please advise?

I would also like to ask the same thing with the ADS1220EVM.

If your answer is different from the ADS124S08, please comment.

1. When using the Delta-Sigma ADC Evaluation Software to connect a 3-wire Pt100 to measure temperature, how do I convert the code value and voltage value displayed in the Data Analysis tab to temperature [℃]?

2. I am measuring by selecting 3-wire RTD in the Scripts tab, how do I change or check the conversion time?

(My coworker previously asked about the conversion time in this email, and I would like to check it with this evaluation board.)

 https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1533088/ads124s08-what-is-the-total-conversion-time-for-using-2-channels-pt100 

3. When selecting 3-wire RTD for measurement, how do I change the filter selection?

4. I understand when switching between the 2 channels of the ADS124S08, it was stated that the settings must be switched for each channel

Is it possible to check the conversion time by making similar settings on the evaluation board?

Also, is it possible to do this with the ADS1220EVM?

5. What does 2048 points/samples mean under Collect Data in the bottom right of the Data Analysis tab?

What will change if I change this?

6. Are the code and voltage values displayed on the Data Analysis tab raw values?

Are they averaged internally and then output?

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru 51846 points

    Hi Shinichi Inoue,

    Here are the answers to your questions

    Shinichi Inoue said:
    1. When using the Delta-Sigma ADC Evaluation Software to connect a 3-wire Pt100 to measure temperature, how do I convert the code value and voltage value displayed in the Data Analysis tab to temperature [℃]?

    There is no direct option to convert code / voltage to temperature using the ADC GUI. You would need external firmware or a calculator to do so.

    We do have temperature sensor example code that can help with the calculation, see here: https://www.ti.com/tool/ADC-TEMP-SENSOR-FW

    Note this code has to be implemented in an external controller, it cannot be ported to the ADC EVM

    Shinichi Inoue said:
    2. I am measuring by selecting 3-wire RTD in the Scripts tab, how do I change or check the conversion time?

    You cannot check the conversion time from the GUI, you will need a logic analyzer or oscilloscope to measure the time between DRDY pulses. This provide you the time between conversions

    Shinichi Inoue said:
    3. When selecting 3-wire RTD for measurement, how do I change the filter selection?

    I am not sure what you mean by "filter selection"? Are you referring to the ADC's digital filter?

    Shinichi Inoue said:

    4. I understand when switching between the 2 channels of the ADS124S08, it was stated that the settings must be switched for each channel

    Is it possible to check the conversion time by making similar settings on the evaluation board?

    There is no good way to multiplex through channels using the EVM. The EVM is intended for evaluation of the ADC, but does not support every use case. I would recommend using the ADS124S08 example code as a base to write a simple program that communicates with the EVM and can multiplex through the channels. Then, use the method in #2 to check the conversion time

    Shinichi Inoue said:
    5. What does 2048 points/samples mean under Collect Data in the bottom right of the Data Analysis tab?

    That means the GUI will collect that number of samples from the ADC and display them on the screen. Note that the default ADC data rate is 20 SPS, so collecting 2048 samples at 20 SPS will take 2048 / 20 = 102 seconds! This is acceptable of course, you will just need to wait 102 seconds for any data to be displayed

    Shinichi Inoue said:
    6. Are the code and voltage values displayed on the Data Analysis tab raw values?

    Yes, these are the raw ADC values. There is no filtering / averaging in software

    -Bryan

  • 0 in reply to Bryan Lizon86
    Guru 21566 points

    Hi Bryan,

    Thank you for your reply and sorry for late reply.

    I sent your answer to the customer.

    When the customer has an additional question, I consult you again.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 21566 points

    Hi Bryan,

    The customer has an additional question.

    Could you please advise?

    ---

    When switching between two channels of the ADS124S08, I think it is necessary to change the register settings for each channel.
    How many msec does it take to switch?

    ---

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Guru 51846 points

    Hi Shinichi Inoue,

    I don't understand what specific information the customer wants to know

    Yes, the customer needs to change the register settings for each channel - are they only changing the INPMUX channel? Are they changing other registers? Is there a specific sequence you can provide to understand what is changing from one channel to the next?

    The time to write a register depends on the SCLK speed, and then the total time it takes depends on the total number of registers that need to be written. As mentioned previously, the actual mux switching is effectively instantaneous, so there is negligible time for the mux to actually switch from one channel to the next. Typically the time between channels is dominated by any external analog settling

    -Bryan

  • 0 in reply to Bryan Lizon86
    Guru 21566 points

    Hi Bryan,

    Thank you for your reply.

    I'll confirm the customer's register setting and feedback to you.

    Could you please wait a couple of time.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Guru 51846 points

    Hi Shinichi Inoue,

    Yes, understood. If the thread locks you are always able to start a new thread, then link back to this thread in case there is important information that we need to review.

    -Bryan