Guard Selection - Keithley 6430 Instruction Manual

Guard selection

Cable guard is used for high-impedance guarding for cables (i.e., coax and triax) and test
fixtures. Ohms guard provides a high-current guard output, which allows in-circuit guarded
ohms measurements.
The guard setting (cable or ohms) only applies to mainframe guard (V,Ω GUARD banana
jack). Cable guard is always available at the Remote PreAmp, regardless of the guard setting.
Ohms guard is only available at the mainframe. On power-up, the mainframe defaults to cable
guard.
NOTE
When the guard selection is changed, the OUTPUT will turn OFF.
Front panel guard selection
Perform the following steps to check or change the guard selection:
1. Press CONFIG and then the SOURCE V, SOURCE I, or Ω. Changing guard in one con-
figuration menu changes it in all of the others.
2. Using the
ENTER.
NOTE Cursor position indicates the present guard selection (OHMS or CABLE). To retain
the present selection, use the EXIT key to back out of the menu structure and skip the
next two steps.
3. To change the guard selection, place the cursor on the alternate selection and press
ENTER.
4. Use the EXIT key to back out of the menu structure.
NOTE
Do not connect ohms guard using coaxial cabling, or oscillations may occur.
Remote command guard selection
Use the :SYSTem:GUARd command in Section 17 to choose between cable and ohms guard
mode via remote. For example, send the following command to enable ohms guard:
:SYST:GUAR OHMS
Conversely, send this command to enable cable guard:
:SYST:GUAR CABL
and keys, place the cursor (flashing menu item) on GUARD and press
Connections 2-13