CAUTION
The maximum voltage between input high
and input low is 26fJV (~&WC maximum on
mA ranges). Exceeding this value may
damage the instrument.
: r
LEGi-
ELECTROMETER
,
EXTERNAL SUPPLY
Figure 4-12. Using the Model 617 with an External
High Voltage Source
Since an external voltage source is used, resistance values can-
not be automatically calculated by the Model 617. You can,
however, simplify these calculations by maintaining a known
ratio between the external value and the programmed voltage
of the Model 617. For example, assume that an external
voltage of 2oOV is used. If you programmed the Model 617
voltage source to 20V. you could easily determine the actual
resistance by noting the displayed value and moving the
decimal point one place to the right.
The same general considerations apply to making voltage
coefficient studies at voltages higher than 10%‘. The basic
configuration shown in Figure 4-12 would be used. As
discussed in paragraph 4.8, the resistance would be measured
at two different voltages, and the resulting voltage coefficient
could then be calculated. As long as a known ratio is main-
tained between the external high voltage and the programmed
voltage of the Model 617, resistance calculations would be
relatively simple.
4-1314-w
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