Keithley 630 Instruction Manual page 10

MODEL 630 POTENTIOMETRIC ELECTROMETER OPERATION
FIGURE 4.
Input Connections to Model 630. The two diagrams show the input circuit for
measuring at ground and for floating.
In A, the unknown voltage has one terminal at ground. The shorting Link is between
the LO and GND Posts of the Model 630.
In B, the unknown voltage has both terminals off ground potential. The floating or
off-ground potential must be less than 500 volts. Also note the shorting line is pe&
used.
b.
The Model 630's high input resistance allows circuit measurements without causing
circuit loading. (See paragraph 2-6.) On the l-millivolt to L-volt null ranges, the in-
put resistance can be set to 1013 er 1010 ohms with the DETECTOR INPUT Switch. Use the
OPEN (1013 ohm input) setting for high source resistances; use the LOLO OHMS setting to
avoid pickup problems or to increase response speed.
resistance is 1010 ohms for either setting.
On ranges above 1 volt, the input
NOTE
When making measurements on devices with high contact resistances (such as
silicon), completely isolate the power supply from ground to avoid measuring
the drop acress the contact resistance.
c. Voltmeter Operating Procedures.
1.
Ten full-scale ranges are available for VTVM operation. When the NULL Switch is
at VTVM, the RANGE Switch determines one of four full-scale ranges.
By putting the five
Reference Voltage Dials at zero, the Model 630 can then operate as a voltmeter on the
six null ranges.
2.
Connect the unknown voltage to the INPUT Receptacle, using the Model 6302 Input
Cable or the Model 6301 Guarded Probe.
When using the guarded probe, use a separate
lead to the LO Terminal.
3.
Switch the RANGE Switch to the most sensitive range for an on-scale meter deflec-
tion.
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