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Question about AD8495

Hi All,

I have a question about the AD8495. Please take a look at the attachment.

I think it is not out of spec, but I would like to know the cause of these variation.

Regards,

Kazu

QuestionaboutAD8495.pdf
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  • Hi Kazu,

    The +/-1.5mV error is the max error you would get if you took the actual output of the AD8495 and subtracted out the polynomial that is correcting for the nonlinearity.  That is the error in mV, which would correspond to less than +/-0.5degC of error over the 0 to 220degC temp range.  The results from the CN-0354 will not be the same as your application - it is using a larger temperature range so the polynomial and subsequent error is different.

    Are you trying to measure down to -25degC?  The curve with the nonlinearity correction will depend on the temperature range used to generate the polynomial.  So if you are measuring down to -25degC, I can generate a polynomial to fit the expected data over the -25degC to 220degC range.  If I just fit the region between -25degC and 0degC and you aren't going to measure there, it won't be very accurate to your application.

    Have you been able to swap out the power supply you are using to generate the inputs?  If you sweep the source over the range you are using for the AD8495, do you have a plot of what that looks like?

    Regards,

    Jordyn

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  • Hi Kazu,

    The +/-1.5mV error is the max error you would get if you took the actual output of the AD8495 and subtracted out the polynomial that is correcting for the nonlinearity.  That is the error in mV, which would correspond to less than +/-0.5degC of error over the 0 to 220degC temp range.  The results from the CN-0354 will not be the same as your application - it is using a larger temperature range so the polynomial and subsequent error is different.

    Are you trying to measure down to -25degC?  The curve with the nonlinearity correction will depend on the temperature range used to generate the polynomial.  So if you are measuring down to -25degC, I can generate a polynomial to fit the expected data over the -25degC to 220degC range.  If I just fit the region between -25degC and 0degC and you aren't going to measure there, it won't be very accurate to your application.

    Have you been able to swap out the power supply you are using to generate the inputs?  If you sweep the source over the range you are using for the AD8495, do you have a plot of what that looks like?

    Regards,

    Jordyn

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