5790B
Operators Manual
4-8
Test Leads and Connectors
Make sure cables and connectors are rated for the voltage that will be used.
Either coaxial or twisted-pair shielded test leads with low-thermal emf connectors
are the best choice. Use short leads to minimize test lead loading. Verify that test
lead loading will not affect your measurement by checking the input impedance
information in Table 4-4. Refer to Loading later in this chapter for more
information.
Coaxial Inputs
Warning
The type "N" connector shells are connected to circuit low and
can float to hazardous voltages if the input is connected
incorrectly.
Use coaxial cable and 50 Ω Type "N" connectors when attaching cables to
INPUT 1 and the WIDEBAND coaxial input connectors. Coaxial cable and “N”
connectors minimize the possibility that radiated electromagnetic energy will
disrupt sensitive measurements. Use the shortest possible length of coaxial
cable. Be aware that if you do add a length of cable, you calibrate the source to
the end of the cable.
Dual Binding Inputs
You can connect test leads to the Product INPUT 2, GUARD, and GROUND
binding posts using banana plugs, spade lugs, or stripped insulated wire. Make
all screw-on connections tight. To avoid errors induced by thermal voltages
(thermal emfs), use connectors and conductors made of copper or materials that
generate small thermal emfs when joined to copper. Avoid using nickel-plated
connectors. Use Fluke Model 5440A-7002 Low Thermal EMF Test Leads for
optimal results.
Table 4-3. Input Test Lead Summary
Input
Connector
Input Frequency
dc to 100 kHz 100 to 300 kHz 300 kHz to 1 MHz 1 to 50 MHz
INPUT 1
TYPE "N"
Coax any
Length
Coax Up to 3 ft
(1 m)
Coax Up to 1 ft
(0.3 m)
N/A
INPUT 2
BINDING
POSTS
Twisted-pair or
coax any length
Twisted-pair or
coax up to 3 Ft.
Twisted-pair or
coax up to 1 ft
(0.3 m)
N/A
WIDEBAND
TYPE "N”
RG-58/U, 3 ft (1 m)
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