Fluke 5522A - Recommended Cable and Connector Types; When to Use EARTH and EXGRD; Earth

Front Panel Operation
How to Connect the Calibrator to a UUT 4
4-9
Recommended Cable and Connector Types
 Warning
To prevent possible electrical shock, fire, or personal injury, do
not touch exposed metal on banana plugs, they can have
voltages that could cause death.
Cables to the calibrator are connected to the NORMAL and AUX terminals. 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. Optimum results can be obtained by using Fluke Model
5440A-7002 Low Thermal EMF Test Leads, which are constructed of well-insulated
copper wire and tellurium copper connectors. (See Chapter 9, “Accessories.”)
When to Use EARTH and EXGRD
Figure 4-1 shows the internal connections made by the Z and B keys.
Chassis ground
Internal guard shield
NORMAL LO
signal ground
NORMAL LO
binding
post
Safety ground
through
ac line cord
Lit = open
Not lit = open
EARTH
EXGRD
GUARD
binding
post
nn003f.eps
Figure 4-1. EARTH and EXGRD Internal Connections
Earth
The Calibrator front panel NORMAL LO terminal is normally isolated from earth
(chassis) ground. When it is desired to make a connection between the NORMAL LO
terminal and earth ground, press the Z key, lighting the key annunciator. When the
earth key is pressed, the NORMAL LO terminal is connected to earth ground through
approximately 30 Ω.
To avoid ground loops and noise you must have only one earth ground-to-LO terminal
connection in the system. Usually you make all signal ground connections at the UUT
and verify the Z annunciator is off. Generally, Z is on only for ac and dc volts
where the UUT is isolated from earth ground. There must, however, be a safety ground
for the Calibrator. See “Connecting to Line Power” in Chapter 2. When enabled by the