Optimizing for High-Resistance Measurements
The techniques required to accurately measure high resistances are somewhat different than those required for low resistances. Electrostatic noise pickup becomes a major concern. To prevent problems with noise pickup, shielding must be considered. Refer to Measuring on the 100 MΩ Range for more information.
Shielding
When measuring resistances >100 kΩ proper shielding is critical. High-resistance measurements are very sensitive to environmental noise such as power line pick up, changes in electrostatic fields caused by people moving nearby, and even RF pickup. For these reasons, it is strongly encouraged to use shielded cables when measuring high resistances. For 2-wire measurements the shield should be tied to the LO terminal. For 4-wire measurements, there are two pairs of shielded cables. The first pair should be tied to HI and LO (shield to LO), and the second pair to HI SENSE and LO SENSE (shield to LO SENSE). Refer to the figure below:
