User`s guide

67
Chapter 3 System Overview
Data Acquisition System Overview
3
System Cabling
The plug-in modules have screw-terminal connectors to make it easy to
connect your system cabling. The type of cabling that you use to connect
your signals, transducers, and sensors to the module is critical to
measurement success. Some types of transducers, such as
thermocouples, have very specific requirements for the type of cable that
can be used to make connections. Be sure to consider the usage
environment when choosing wire gauge 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.
Note: Wiring insulation and usage is described in more detail in "System
Cabling and Connections" starting on page 257.

Cable Type Common Uses Comments
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.
34970A Refresh UG.book Page 67 Wednesday, February 17, 2010 12:34 PM