Keithley 2461 Quick Start Manual page 25

The voltage measurements appear in the Measure Voltage area of the
Home screen.
To save the data to a USB flash drive:
1. Insert a USB flash drive into the front panel USB connector.
2. Press the MENU key.
3. Under Measure, select Reading Buffers.
4. Select defbuffer1. A menu is displayed.
5. Select Save To USB.
6. Enter the file name.
7. Select OK (on the screen).
8. A confirmation message is displayed. Select Yes.
The instrument saves the data to a .csv file on the flash drive.