Accuracy of PXIe-6570 PPMU Measure Voltage

[SongU]

Hello,

This might be a very simple question. I am confused about the resolution and accuracy definition of PXIe-6570 when measuring voltage. In its specifications, the resolution is 228 uV and the accuracy is +-5mV. What I understand the resolution is that the mininum voltage interval it can tell is 228uV. Is it right? Dose 'Accuracy +-5mV' here mean that the result might drift (plus 5mV or minus 5mV)? Does it mean if I measure a voltage in the range of 5mV to -5mV, I cannot get accurate result? Many thanks!

Best wishes,

SongU

[Valentin87]

I think: if you measure 1.000000V, the result can be 0.995V+-228 uV to 1.005V+- 228uV.

https://en.wikipedia.org/wiki/Accuracy_and_precision#/media/File:Accuracy_and_precision.svg

[SongU]

Thank you Valentin.I guess so. So it means basically it cannot measure voltage below 5mV like 1mV?

But +-5mV is quite inaccurate since my multimeter can measure 0.1mV DC voltage...LOL

[Valentin87]

When I force voltage from PXIe-6556 = 2V, example from NI measure up to 2.000+-100uV, and usual multimeter measure up to 2.000V, so very close. If need, i get pictures later.