Guarding; Figure 3-1 Voltage Measurements - Keithley 6517B User Manual

Model 6517B Electrometer User's Manual
Figure 3-1
Voltage measurements
A. Unguarded (GUARD off)
B. Guarded (GUARD on)

Guarding

Guarding should be used for high impedance (>10
measurements when using long input cables. In a high impedance circuit, guarding greatly
reduces leakage currents. When using long input cables, guarding cancels the effects of cable
capacitance that can significantly slow down the measurement response time.
When GUARD is enabled, the INPUT triax connector is reconfigured to apply the guard potential
to the inner shell of the INPUT triax connector. With this configuration, the COMMON banana jack
is used for input low.
INPUT connector.
Perform the following steps to enable or disable guard:
1.
2.
3.
4.
6517B-900-01 Rev. A / Jun 2008
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
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Figure 3-1
Press CONFIG and then V to display the volts configuration menu.
Use the and keys to place the cursor (blinking menu item) on GUARD and press
ENTER.
Place the cursor on the desired selection (OFF to disable or ON to enable) and press
ENTER.
Use the EXIT key to back out of the menu.
Return to Section Topics
9 Ω) voltage measurements and for voltage
shows both the guarded and unguarded configurations for the
Section 3: Basic Measurements
3-3