When does the 4339B display "OVLD"?

"OVLD" message is displayed when the following conditions are met:
1. Measured input current is higher than the selected current measurement range.
2. The current measurement range suitable for the DUT measurement is not compatible with the measurement time mode setting. As a result, the selected current measurement range is lower than the appropriate range.

When the OVLD message is displayed, perform as follows:
1. Check if the current measurement range is properly set for the magnitude of measurement input current. Try setting the 4339B to auto range mode.
2. Verify that measurement time mode setting (Short, Medium or Long) is applicable to the current measurement range used for the DUT measurement.

The selectable current measurement ranges and measurement time modes are shown in Table 8-1 in Section 8 of the 4339B Operation Manual.