Table Of Contents

Examples of Calculating Accuracy Specifications[1]

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    Last Modified: August 16, 2021

    Example 1: Calculating 5 °C Accuracy

    Calculate the accuracy of 900 nA output in the 1 µA range under the following conditions:

    Ambient temperature 28 °C
    Internal device temperature within Tcal ±5 °C[2]
    Self-calibration within the last 24 hours

    Solution

    Because the device internal temperature is within Tcal ±5 °C and the ambient temperature is within 23 °C ±5 °C, the appropriate accuracy specification is the following value:

    0.03% + 100 pA

    Calculate the accuracy using the following formula:

    Accuracy = 900 nA * 0.03 % + 100 pA    = 270 pA + 100 pA

    = 370 pA

    Therefore, the actual output is within 370 pA of 900 nA.

    Example 2: Calculating Remote Sense Accuracy

    Calculate the remote sense accuracy of 500 mV output in the 600 mV range. Assume the same conditions as in Example 1, with the following differences:

    HI path lead drop 3 V
    HI sense lead resistance 2 Ω
    LO path lead drop 2.5 V
    LO sense lead resistance 1.5 Ω

    Solution

    Because the device internal temperature is within Tcal ±5 °C and the ambient temperature is within 23 °C ±5 °C, the appropriate accuracy specification is the following value:

    0.02% + 50 μV

    Because the device is using remote sense, use the following remote sense accuracy specification:

    Add 3 ppm of voltage range per volt of HI lead drop plus 1 μV per volt of lead drop per Ω of corresponding sense lead resistance to voltage accuracy specifications.

    Calculate the remote sense accuracy using the following formula:

    Accuracy = ( 500 mV * 0.02 % + 50 μV ) + 600 mV * 3 ppm 1 V of lead drop * 3 V + 1 μ V V * Ω * 3 V * 2 Ω + 1 μ V V * Ω * 2.5 V * 1.5 Ω    = 100 μV + 50 μV + 1.8 μV * 3 + 6 μV + 3.75 μV = 165.15 μV

    Therefore, the actual output is within 165.15 µV of 500 mV.

    Example 3: Calculating Accuracy with Temperature Coefficient

    Calculate the accuracy of 900 nA output in the 1 µA range. Assume the same conditions as in Example 1, with the following differences:

    Ambient temperature 15 °C

    Solution

    Because the device internal temperature is within Tcal ±5 °C, the appropriate accuracy specification is the following value:

    0.03% + 100 pA

    Because the ambient temperature falls outside of 23 °C ±5 °C, use the following temperature coefficient per °C outside the 23 °C ±5 °C range:

    0.0006% + 4 pA

    Calculate the accuracy using the following formula:

    Temperature Variation = ( 23 ° C 5 ° C ) 15 ° C = 3 ° C

    Accuracy = ( 900 nA * 0.03 % + 100 pA ) + 900 nA * 0.0006 % + 4 p A 1 ° C * 3 ° C

       = 370 pA + 28.2 pA

    = 398.2 pA

    Therefore, the actual output is within 398.2 pA of 900 nA.

    • 1 Specifications listed in examples are for demonstration purposes only and do not necessarily reflect specifications for this device.
    • 2 Tcal is the internal device temperature recorded by the PXIe-4135 at the completion of the last self-calibration.

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