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pga309 evm calibration Vout can not reach my setting

yao Tim
Intellectual 270 points
Other Parts Discussed in Thread: PGA309

1 .  i use PGA309 evm to calibrate my bridge sensor.but now have one problems.that is the Vout is not reach my setting after calibration.my setting is Vout :max 4.5V,min 0.5.real Vout is  :max  4.2V,min 0.055V,i am confused,who know the reasion? the picture below is my calibration. Vout in red box

 

2. i have designed one NEW  PCB board which contain  PGA309 and EEPROM.i also design one PRG port. on my new board .my question is:

can i connect  my new PCB board  PRG port to PGA309 USB-DAQ-platform  PRG port to calibrate my bridge sensor.and  then download result into EEPROM?   After that  just need to connect TEST pin to GND  and then my new board will work.

  • 0
    TI__Mastermind 27715 points

    Hello Yao,

    1. Are these the results of your attempted calibration, or was calibration successful and you simply can't get accurate output when you run a post-calibration test? Do you have a power supply voltage of at least +4.8V? Can you post your pre-cal file for me to review?

    2. Yes, you can connect the 1W and GND nodes from the USB-DAQ platform to your PCB to program it during calibration.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

  • 0 in reply to Ian Williams
    Intellectual 270 points

    hello Williams,

    1.i use internal  power supply  4.096V.

       yes,the output voltage is not the same to my pre-cal setting.

       i use RT-  mode.  picture below is my connections

      

          this is my pre-cal file  :

    7457.v_4wire_p5_4p9.txt 
    [PGA309_Settings]
Numb Reg=3
Poly Order=2
Output Mode=0
Vout_High_Target=4.500000
Iout_High_Target=0.000000
Iout_Low_Target=0.000000
Vout_Low_Target=0.500000
Vs=5.000000
Vref=4.096000
Calibrate Nonlin=TRUE
Reg0=0
Reg1=0
Reg2=0
Reg3=1280
Reg4=0
Reg5=0
Reg6=5135
Reg7=0
Reg8=0
Temp0=10.000000
Temp1=25.000000
Temp2=60.000000

     

     

     

     

     

     

     

  • 0 in reply to yao Tim
    TI__Mastermind 27715 points

    Hello Yao,

    Your drawing of the bridge sensor connections is correct for Rt- mode. Your pre-cal file also looks correct.

    Are you using the sensor emulator for calibration, or your real bridge sensor connected to the PGA309EVM?

    Best regards,

    Ian Williams

  • 0 in reply to Ian Williams
    Intellectual 270 points

    hi Williams,

    i redraw  a picture of my setting;  use real sensor.

     i use the sensor emulator for calibration with diode mode,the result is right.

    just only use real sensor for calibration ,the result is not right.for example:

    Output  voltage  my  pre-cal set is 0.5V-4.5V,but result is 0.055V-4.2V.I think the result of my calibration  should  be  same to pre-cal setting.

  • 0 in reply to Ian Williams
    Intellectual 270 points

    hello  Williams,

    i think maybe is my Zero Dac  value and  Gain  Dac  value  are  wrong.my Zero Dac  value and  Gain  Dac  value  are  2.18 and 3.20.do you know the reasons ?