• State
  • Locked Locked
  • Replies 8 replies
  • Subscribers 31 subscribers
  • Views 590 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PGA300: PGA300

Ed Payne
Intellectual 375 points
Part Number: PGA300

Compound Transducer -15 psi to +30 psi with PGA300

When calibrated:

  • Calibration point #1: -13.5 psi / 4.428 mA / HEX 818 (based to -14.7 psi / 4.0 mA / HEX 766)
  • Calibration point #2: 0 psi / 12 mA / HEX 1800
  • Calibration point #3: 30 psi / 20 mA / HEX 2700

When verified:

  • Calibration point #1: 0.1% accuracy
  • Calibration point #2: up to 4.5% accuracy, I can manually try hex and adjust it to achieve 0.2% later.
  • Calibration point #3: 0.1% accuracy

Please advise, thanks.

  • 0
    TI__Mastermind 31655 points

    Hello Ed,

    Can you please show a screenshot of the GUI's calibration page? It would be helpful to see the ADC data during the calibration, and during the verification portion could you also place the PGA300 in reset and read the ADC values from the ADC settings page to see what the raw data shows for each of the calibration points? I would like to make sure that the input is the same in both the calibration and verification stages.

    Regards,

    Scott

  • 0 in reply to Scott Cummins
    Intellectual 375 points

    1) During calibration

    2) During verifying

    3) Tune-up by manually changing HEX @ 0 psi

    • FFF3 HEX = 1.202 psi (calibration hex with real pressure reading)
    • 0 HEX = 1.107 psi
    • 90 HEX = 0.099 psi
    • 99 HEX = 0.038 psi (BEST Point)
    • 100 HEX = -0.634 psi
    • 101 HEX = -0.640 psi

    There is abrupt jump at 100 HEX

    Please advise.

  • 0 in reply to Ed Payne
    TI__Mastermind 31655 points

    Hi Ed,

    It looks like your inputs are very consistent, but according to the DAC calibration window it looks like you are setting the desired output to 9.68mA for the middle pressure point instead of 12mA as you described before. Is there a reason for this change?


    Regards,

    Scott

  • 0 in reply to Scott Cummins
    Intellectual 375 points

    Hi Scott,

    9.68 mA = 4 mA + (20 mA - 4 mA) * (( 0 psi - (-14.7 psi)) / ((30  psi - (-14.7 psi))

    Thanks a lot.

    Ed

  • 0 in reply to Ed Payne
    Intellectual 375 points

    Hi Scott,

    Could you please answer this question?

    Ed

  • 0 in reply to Ed Payne
    TI__Mastermind 31655 points

    Hi Ed,

    Since the input is quite consistent at the middle point between the calibration and the verification, it looks like this may be a tricky calibration for the coefficient calculation. Can you also show the coefficients and digital scaling that are calculated and displayed in the digital EEPROM page?

    What is the PADC_gain on the digital EEPROM page? If the value is more than 1, it will be helpful to increase the PGAIN in the analog EEPROM to counter this. It will likely result in a better calibration.


    Regards,
    Scott

  • 0 in reply to Scott Cummins
    Intellectual 375 points

    Hi Scott,

    PADC_gain on the digital EEPROM page was automatically generated as 1. If It needs to be changed for better accuracy, what is the rule to change it?

    Thanks again.

    Ed

  • 0 in reply to Ed Payne
    TI__Mastermind 31655 points

    Hi Ed,

    If it is already set as 1 that is the ideal setting. If it were higher than 1, then it would be useful to set the analog PGAIN to a higher value to avoid the need for additional digital gain.

    Let me look into this a bit more and get back to you later this week.

    Regards,