No, actually I don´t know about the probes, since 0.1 mV is a very accurate measure.
I´ve done an experiment using common wire tho detect if a cloth is getting wet. The connections I used were:
(+) probe connected to Arduino +5V (assuming an UNO or another 5V signal board)
(-) probe connected to any Analogic Port of Arduino
a pull-down resistor from this Analogic port to GND, to ensure a zero value reading if no imput comes from the probe.