AD7193 Accuracy Issues...

   Hello,

AD7193 calibration issue is solved & now i am getting values of offset register & Full scale register as follows.

      Offset register=8389236

      Full scale register=5584950

  AD7193 Configured as follows:

Mode register=0x0C0060

Configuration register=0x040118

Gain=1, Vref1=2.5, Chop disable, FS[9:0]=96,Continuous conversion mode,unipolar configuration

0 to 2.5V dc input connected to ch1 to check linearity of  ADC.

But i am getting 3.5% error (of the reading) near 0.1V

Zero: 0v , ADC counts=0

Span: 2.5V, ADC counts = 16754713

i/p                   ADC counts          Calculated Counts        Error(%)

0.10001          644500                     670228                     3.8387

0.20001         1315798                   1340390                    1.8346

0.30001         1987091                    2010551                   1.1668

0.4001            2660577                   2681316                   0.7734 

0.5001            3331311                   3351478                   0.6017

0.6001            4002490                   4021639                   0.4761

.......

.......

2.0001            13398607                  13403902                0.0394

2.2001            14741788                  14744225                0.0165

2.4001            16083274                  16084548                0.0079

2.5001            16754713                  16754713                

 

 

Please help me how to minimize Error..

Expected error for my application should be <.25% of the reading near zero.

 

Any help will greatly appreciated...

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  • 0
    •  Analog Employees 
    on May 27, 2018 5:44 PM

    Hi,

    Does your measurement requires faster ODR? If not, can you try to enable chopping? With chopping enabled, the offset equals ±0.5 uV typical. Therefore, chopping gives an improvement in offset for gains of 1 to 64. The offset drift is better when chopping is enabled for gains of 1 to 16. May I know if you are using internal or external reference? How your inputs connected? On your configuration register, does your buffer enable? If yes, the inputs should meet the buffer headroom, otherwise linearity and noise performance degrade. If you could also share us the schematic or setup of your measurements it would be great. Since you are targeting precision measurements, care must be taken on the said setup as longer wires or improper grounding connections may introduce some noise and errors.

    Thanks,

    Jellenie

Reply
  • 0
    •  Analog Employees 
    on May 27, 2018 5:44 PM

    Hi,

    Does your measurement requires faster ODR? If not, can you try to enable chopping? With chopping enabled, the offset equals ±0.5 uV typical. Therefore, chopping gives an improvement in offset for gains of 1 to 64. The offset drift is better when chopping is enabled for gains of 1 to 16. May I know if you are using internal or external reference? How your inputs connected? On your configuration register, does your buffer enable? If yes, the inputs should meet the buffer headroom, otherwise linearity and noise performance degrade. If you could also share us the schematic or setup of your measurements it would be great. Since you are targeting precision measurements, care must be taken on the said setup as longer wires or improper grounding connections may introduce some noise and errors.

    Thanks,

    Jellenie

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