User`s guide

6 Agilent 34980A Mainframe User’s Guide
1 Introduction to the 34980A
Plug-In Modules
The 34980A offers a complete selection of plug- in modules to give you
high- quality measurement, switching, and control capabilities. The
plug- in modules communicate with the main system processor via the
internal digital bus. The multiplexer modules also connect to the internal
DMM via the internal Analog Buses. Each module has its own
microprocessor to offload the main system processor and minimize
backplane communications for faster throughput. See Chapter 4,
“Introduction to the Plug- In Modules for the 34980A” for an overview of
the available plug- in modules and their functions. Each module is
shipped with its own User's Guide.
System Cabling
Depending on your specific requirements, you can connect your device
under test (DUT) to the 34980A using several optional interconnection
solutions (see “Interconnection Solutions Overview” on page 167).
Detachable terminal blocks are available for low- frequency modules and
offer an extremely flexible method for connecting external wiring. You
can also connect to the plug- in modules directly using standard cabling
with 50- pin D- Sub and 78- pin D- Sub connectors. Optional solder cup
connector kits are also available if you choose to build your own custom
cabling.
The type of cabling that you use to connect your signals, transducers,
and sensors to the module is critical to ensure measurement integrity.
Some types of transducers, such as thermocouples, have very specific
requirements for the type of cabling that should be used to make
connections. Be sure to consider the usage environment when choosing
wire gauge size and insulation qualities. Wire insulation typically consists
of materials such as PVC or PTFE. The table below lists several common
cable types and describes their typical uses.
Cable Type
C o m m o n U s e s C o m m e n t s
Thermocouple
Extension Wire
Thermocouple
measurements
Available in specific thermocouple types.
Also available in a shielded cable for added
noise immunity.
Twisted Pair,
Shielded Twisted
Pair
Measurement inputs,
voltage outputs,
switching, counting
Most common cable for low-frequency
measurement inputs. Twisted pair reduces
common mode noise. Shielded-twisted pair
provides additional noise immunity.
Shielded
Coaxial,
Double-Shielded
Coaxial
VHF Signal switching Most common cable for high-frequency
signal routing. Available in specific
impedance values (50 or 75). Provides
excellent noise immunity. Double-shielded
cable improves isolation between channels.
Requires special connectors.
Flat Ribbon,
Twisted Pair
Ribbon
Digital Input/Output Often used with mass termination
connectors. These cables provide little
noise immunity.