Keithley SourceMeter 2400 Series - Cable Guard; Figure 5 Cable Guard Connections; Ohms Guard

8 Quick Results Guide
Cable guard
When testing high-impedance DUT (>1G Ω ), cable guard is used to drive the shields of
cables and test fixtures to minimize leakage currents and input capacitance. A typical connec-
tion scheme using cable guard is shown in Figure 5. The following menu sequence selects
cable guard:
Press CONFIG > press SOURCE V (or SOURCE I or MEAS
Ω ) > select GUARD > select
CABLE
The guard terminal of the SourceMeter is at virtually the same potential as input/output HI.
Therefore, if there is hazardous voltage at input/output HI, it is also present on the guard shield
for the test circuit.
WARNING To prevent injury from electric shock, the guard shield must be enclosed in
a safety shield (i.e., test fixture) that is connected to safety earth ground (as
shown in Figure 5).
Ohms guard
Ohms guard allows in-circuit resistance measurements on DUT where other parasitic leak-
age devices are present. Connection schemes for a Delta DUT configuration is shown in
Figure 6.
INPUT/
OUTPUT
4-WIRE
SENSE
HI
LO
IEEE-488
(ENTER IEEE ADDRESS
WITH FRONT PANEL MENU)
V, Ω
GUARD
GUARD
SENSE
WARNING:NO INTERNAL OPERATOR SERVICAB
CAUTION:FOR CONTINUED PROTECTION AGAINST FIR
RS232
DUT
Connect to earth safety ground
using #18 AWG wire or larger.
Guard Shield
Test Fixture
Figure 5
Cable guard connections