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PPM Calculation In Resistor

Discussion in 'Datasheets, Manuals and Component Identification' started by rssuresh_eee, Apr 1, 2013.

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  1. rssuresh_eee


    Apr 1, 2013

    In my Circuit using 499ohm 0.1% with 0.2ppm in one of the voltage divider section Part No: VFC1206 499R00 BBT.
    The mentioned part is absolute. Not possible to get the same one in short period. But in my company having same resistor and tolerance but only one difference is PPM. 5PPM only available.
    Plz tel me what is the role of PPM in TCR calculation and how to calculate.
    Can I use 5PPM resistor
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Presumably the resistor is 0.2ppm/degC.

    We can't answer your question.

    You need to calculate how much variance from the nominal resistance is acceptable and whether a 0.5ppm/degC resistor will be within that limit for the range of temperatures expected.

    Lets say you can tolerate 0.11% variation. 0.1% comes from the tolerance, that leaves 0.01%, which is 100 parts per million. At 5ppm/degC, a variation of 20C will take you out of spec. At 0.2ppm/degC temperature will not put you out of spec.

    But more importantly, if this is a part of (say) a voltage divider, it may vary with temperature more than other higher specced resistors and this may be an issue.

    If this is an R/2R network, changes in the resistor valuess can cause errors much greater than 1 bit. Higher specced resistors allow you to extend the network to more bits.
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