# Examples of Calculating Accuracy Specifications[1]

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## 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:

$\mathrm{Accuracy}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}900\text{\hspace{0.17em}}\mathrm{nA}*\text{\hspace{0.17em}}0.03%\text{\hspace{0.17em}}+\text{\hspace{0.17em}}100\mathrm{pA}$ $\text{\hspace{0.17em}\hspace{0.17em}}=\text{\hspace{0.17em}}270\mathrm{pA}+\text{\hspace{0.17em}}100\mathrm{pA}$

$=\text{\hspace{0.17em}}370\mathrm{pA}$

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:

$\mathrm{Accuracy}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}\left(500\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{mV}*\text{\hspace{0.17em}}0.02%\text{\hspace{0.17em}}+\text{\hspace{0.17em}}50\text{\hspace{0.17em}}\mathrm{\mu V}\right)+\text{\hspace{0.17em}}\frac{600\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{mV}*\text{\hspace{0.17em}}3\text{\hspace{0.17em}}\mathrm{ppm}}{1\text{\hspace{0.17em}}V\mathrm{of}\text{\hspace{0.17em}}\mathrm{lead}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{drop}}*\text{\hspace{0.17em}}3\text{\hspace{0.17em}}V+\text{\hspace{0.17em}}\frac{1\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mu V}{V*\text{\hspace{0.17em}}\mathrm{\Omega }}*\text{\hspace{0.17em}}3\text{\hspace{0.17em}}V\text{\hspace{0.17em}}*\text{\hspace{0.17em}}2\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{\Omega }+\text{\hspace{0.17em}}\frac{1\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mu V}{V*\text{\hspace{0.17em}}\mathrm{\Omega }}\text{\hspace{0.17em}}\text{\hspace{0.17em}}*\text{\hspace{0.17em}}2.5\text{\hspace{0.17em}}\text{\hspace{0.17em}}V*\text{\hspace{0.17em}}1.5\mathrm{\Omega }\text{\hspace{0.17em}}$ $\text{\hspace{0.17em}\hspace{0.17em}}=\text{\hspace{0.17em}}100\mathrm{\mu V}+\text{\hspace{0.17em}}50\mathrm{\mu V}+\text{\hspace{0.17em}}1.8\mathrm{\mu V}*3+\text{\hspace{0.17em}}6\mathrm{\mu V}+\text{\hspace{0.17em}}3.75\mathrm{\mu V}$ $=\text{\hspace{0.17em}}165.15\mathrm{\mu V}$

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:

$\mathrm{Temperature}\mathrm{Variation}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}\left(23\text{\hspace{0.17em}}°C-\text{\hspace{0.17em}}5\text{\hspace{0.17em}}\text{\hspace{0.17em}}°C\right)\text{\hspace{0.17em}}-15°C=\text{\hspace{0.17em}}3\text{\hspace{0.17em}}°C\text{\hspace{0.17em}}$

$\mathrm{Accuracy}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}\left(900\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{nA}\text{\hspace{0.17em}}*\text{\hspace{0.17em}}0.03%\text{\hspace{0.17em}}+\text{\hspace{0.17em}}100\text{\hspace{0.17em}}\mathrm{pA}\right)+\text{\hspace{0.17em}}\frac{900\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{nA}*\text{\hspace{0.17em}}0.0006%\text{\hspace{0.17em}}+4\text{\hspace{0.17em}}pA}{1\text{\hspace{0.17em}}°C\text{\hspace{0.17em}}}*\text{\hspace{0.17em}}3\text{\hspace{0.17em}}\text{\hspace{0.17em}}°C$

$\text{\hspace{0.17em}\hspace{0.17em}}=\text{\hspace{0.17em}}370\text{\hspace{0.17em}}\mathrm{pA}+\text{\hspace{0.17em}}28.2\text{\hspace{0.17em}}\mathrm{pA}$

$=\text{\hspace{0.17em}}398.2\text{\hspace{0.17em}}\mathrm{pA}$

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.