Keithley 6514, Instruction Manual, Page: 61 / 334

3-4 Volts and Ohms Measurements
Volts and ohms measurement procedure
CAUTION The maximum input voltage to Model 6514 is 250V peak. Exceeding this
value may cause damage to the instrument that is not covered by the
warranty.
WARNING The maximum common-mode input voltage, which is the voltage between
the input (HI or LO) and chassis ground, is 500V peak. Exceeding this value
may create a shock hazard.
Step 1 Enable zero check and select the volts (V) or ohms (
Ω
) function
Zero check should always be enabled before making function or connection changes. The
ZCHK key toggles zero check on and off. When on, the “ZC” or “ZZ” message is displayed. See
Section 2 for details on zero check.
The volts function is selected by pressing the V key, and the ohms function is selected by
pressing the Ω key.
NOTE
Zero check will enable whenever the ohms function is selected.
Step 2 Enable or disable guard
The GRD key toggles the driven guard on and off. If performing unguarded measurements,
press GRD until the “GUARD OFF” message is displayed. If performing guarded measure-
ments, press GRD until the “GUARD ON” message is displayed.
WARNING Hazardous voltage may be present on the inner shield of the triax cable
when GRD is on. A metal safety shield connected to safety earth ground (as
shown in Figure 3-5) must be used for voltage measurements at or above
30V.
Step 3 Perform zero correction (volts only)
To achieve optimum accuracy for low voltage measurements, it is recommended that you zero
correct the electrometer. To do so, select the 2V range (which is the lowest range) and press the
ZCOR key until the “ZZ” message is displayed. See Section 2 for details on zero correction.
Step 4 Select a manual measurement range or enable auto range
Use the RANGE and keys to select a manual measurement range, or press AUTO to
enable auto range. With auto range enabled, the instrument will automatically go to the most
sensitive range to make the measurement. See Section 6 for details on range.