Why does the system lock up while measuring high ‘negative resistance’?

High negative resistance (as observed in bulk current measurements on PMOS transistors) may result in SMU oscillation. This oscillation results in a special case for the auto ranging circuitry of the SMU. This special case resulted in a system lockup with KTE Interactive 4.3.2. Service Pack 1 (SP1) resolves the lockup problem. Contact Keithley service for an SP1 installation CD.