Low Voltages
When setting up systems using relay switching, keep in mind that low–voltage performance is largely limited by the switches selected and the input terminals used on the switch.
Good low–thermal relay switching cards are available from NI.
Common, uncompensated reed relays can reach tens of µV of rather unstable offset, but high–performance reeds can reach below 1 µV.
Many armature–style latching reed relays can give very low drift (one such device is used in the NI 4065 and NI 4070/4071/4072 signal path). It is sometimes possible to compensate for this drift by using similar relays in both HI and LO connections or by placing adjacent poles of a 2–pole relay back–to–back.
Lastly, a common metrology technique involves making a measurement, reversing the leads, taking another measurement, and subtracting and averaging the two readings.