Resistance Standards
Operating Notes
Operating Notes
This part of the manual explains operational and environmental considerations
for the 742A Series. Follow these guidelines when operating or storing the
resistance standard. Precautions for handling are under “Care and Maintenance.”
Connecting to the 742A Series
Caution
Do not apply voltages above the maximum voltage printed on
the front panel. Excessive voltage can cause a permanent shift
in resistance values or damage.
The specifications for models with CURRENT and SENSE binding posts require
four-wire connections to the standard. Use these binding posts as described in
Table 2.
For the case to act as a shield, the CHASSIS GROUND binding post must be
connected to earth ground or instrumental guard at some point in a calibration
system. Normally when two or more instruments with guards are connected
together, the use of a single common grounding point avoids ground loops. If
applicable, ground the 742A CHASSIS GROUND binding post to that common
grounding point.
Figure 3 shows a typical connection to a four-wire ohmmeter. Figure 4 shows the
connection used to calibrate the 1
Ω
internal resistance standard in the 5700A.
Cable Recommendations
For optimum results, use two sets of the Fluke 5440A-7004 Low Thermal Test
Leads, which are designed to reduce errors caused by thermal emfs.
Figure 3. Connection to a Four-Wire Ohmmeter
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