Keithley 6517A, Getting Started Manual

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1-12 Front Panel Operation Model 6517A Getting Started Manual
Guarding
Guarding should be used for high impedance (
≥
10
9 Ω
) voltage measurements and for volt-
age measurements that use 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. Figure 1-3 shows both the guarded and
unguarded configuration of the INPUT connector.
Perform the following steps to enable or disable guard:
1. Press CONFIG and then V to display the volts configuration menu.
2. Use the and keys to place the cursor (blinking menu item) on GUARD and
press ENTER.
3. Place the cursor on the desired selection (OFF to disable or ON to enable) and
press ENTER.
4. Use the EXIT key to back out of the menu.
Current measurements
Assuming “BENCH” reset conditions, the basic procedure is as follows:
1. With zero check enabled (“ZeroCheck” displayed), select the amps function by
pressing I. The Z-CHK key is used to enable/disable zero check.
2. To achieve optimum accuracy for low current measurements, zero correct the
Model 6517A. To do this, use the RANGE
key to select the lowest measurement
range (20pA) and press REL. With zero correct enabled, the REL indicator is on,
and the message “ZCor” is displayed.
3. Select a measurement range or use autoranging:
a. To automatically select the most sensitive range, enable autorange. The AUTO
key enables and disables autorange. When enabled, the AUTO annunciator is
on.
b. For manual ranging, use the RANGE and keys to select a measurement
range consistent with the expected current.