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Improve AD8218 accuracy

Question asked by DanTheMan on Sep 13, 2013
Latest reply on Sep 16, 2013 by Emman.A

I need to measure high side current 0-24mA, with a high accuracy 0.1mA, during a -10 - +125deg temperature.

The AD8218 seems to be a nice component, but when i starting to calculate there are way to inaccurate. Most of the error is comming from GAIN and Voltage Offset errors. I can do callibration in the production of each product, to eventually improve accuracy, but I need to understand whats the datasheet say to me. Please help me to demystify the values below:

 

from datasheet:

http://www.analog.com/static/imported-files/data_sheets/AD8218.pdf

 

Gain Initial Accuracy                                  Typ:+-0.1%                                     

     Is this a gain offset at 25C, that can be removed by calibration in 25C?

 

Gain Initial Accuracy over temperature         Max:+-0.35%

      Is this a gain offset at whole temp range? In this case why is then +-5ppm/C stated? Can this be removed by calibration in 25C?

 

Gain Initial Temp vs temperature                  +-5ppm/C

      Normally I would beleve that this is the gain change over temperature but whit a  Gain Initial Accuracy over temperature in the datasheet I      dont know what this data means any more?

 

Voltage Offset-Voltage Offset                                    Max:+-200uV                                     

     Is this a Voltage offset at 25C, that can be removed by calibration in 25C?

 

Voltage Offset-Voltage Offset Over Temperature        Max:+-300uV                                     

      Is this a Voltage Offset at whole temp range? In this case why is then +-100nV/C stated? Can this be removed by calibration in 25C?

 

Voltage Offset-Offset Drift                                       +-100nV/C                                    

      Normally I would beleve that this is the Offset change over temperature but whit a  Voltage Offset-Voltage Offset Over Temperature in the       datasheet I dont know what this data means any more?

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