Rockwell Automation 1790-TXXXX CompactBlock LDX I/O Profibus Analog, RTD and Thermocouple - Manual (Page 10)

10
Publication 1790-IN010B-EN-P - April 2003
Connect Field Wiring
System Wiring Guidelines
Follow these guidelines when wiring your system:
• Use shielded, twisted pair wire to ensure proper operation
and high immunity to electrical noise.
• To limit noise, locate RTD and resistance device signal wires
as far away as possible from power lines, load lines and
other sources of electrical noise, such as hard-contact
switches, relays and AC motor drives.
• Under normal conditions, connect the drain wire and shield
junction to earth ground, via a panel or DIN rail mounting
screw at the block end.
• Keep shield connection to ground as short as possible.
• To ensure optimum accuracy, limit overall cable impedance
by keeping the cable as short as possible. Locate the I/O
system as close to your field devices as your application will
permit.
RTD Wiring Guidelines
Since the operating principle of the RTD module is
based on the measurement of resistance, give special
consideration when selecting the input cable. For 2-wire
or 3-wire configurations, select a cable that has
consistent impedance throughout its entire length.