User Manual

2400 Series SourceMeter
®
User’s Manual Ohms Measurements 4-9
Ohms accuracy calculations
Example accuracy calculations for various combinations of source readback, off-
set compensation, and normal/enhanced mode are shown below. See
Appendix A for detailed specifications.
Ohms accuracy of 100mΩ @ 5mA source current, normal mode
Source readback OFF, Offset Compensation OFF
Ohms accuracy = Isource accuracy + Vmeas accuracy:
I source accuracy = (5mA) (0.045%) + 2µA
2.25µA + 2µA = 4.25µA
4.25µA / 5mA = 0.085%
Vmeasure accuracy for (100mΩ) (5mA) = 500µV:
(500µV)(0.012%) + 300µV
60nV + 300µV = 300.06µV
300.06µV / 500µV = 60.01%
Total Ohms Uncertainty
60.01% + 0.085% = 60.09%
100mΩ
± 60.09% = 39.9mΩ to 160.09mΩ
Ohms accuracy of 100mΩ @5mA source current, normal mode
Source Readback ON
Ohms accuracy = Imeas accuracy + Vmeas accuracy:
Imeasure accuracy = (5mA) (0.035%) + 600nA
1.75µA + 600nA = 2.35µA
2.35µA / 5mA = 0.047%
Vmeasure accuracy = (500µV)(0.012%) + 300µV
60nV + 300µV = 300.06µV
300.06µV / 500µV = 60.01%
Total Ohms uncertainty:
60% + 0.047% = 60.06%
100mΩ
± 60.06% = 39.94mΩ to 160.06mΩ