Keithley 2461, Reference Manual, Page: 355 / 1109

Model 2461 Interactive SourceMeter® Instrument Reference Manual Section 4: Source-measure considerations
2461-901-01 A/November 2015 4-19
Calculating source or measure accuracy
The source and measure accuracy specifications are expressed as a percent of reading or source
value and an offset. To calculate source accuracy, use the formula:
Accuracy
= ± ( %
of reading
+
offset)
For example, assuming:
•
Current output = 100 mA on 100 mA range
•
Accuracy specification = ± (0.020 % of 15 µA)
Calculate the current source accuracy as shown in the following equations.
Error = {(100 mA * 0.0002) + 15 µA}
= ± {20 µA + 15 µA}
= ± 35 µA
Thus, the current output in this example could fall anywhere within the range of 100 mA ± 35 µA, an
uncertainty of ± 0.035 %.
Calculate accuracy of a resistance measurement made by sourcing I
and measuring V
This example shows how to use the summation method to calculate the accuracy of a resistance
measurement made by sourcing current and measuring voltage. With this method, the accuracy of
the source and measurements are found separately and then added together.
Device to be measured = 20
Ω resistor using 100 mA test current
Current source accuracy:
Current output = 100 mA on 100 mA range
Accuracy specification = ± (0.02 % of 15 µA)
Error = ± {(100 mA x 0.0002) + 15 µA}
= ± {20 µA + 15 µA}
= ± 35 µA
Error % =± 0.035 %