Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation - Manual (Page 22)

Chapter 2
Installing a Network
2–9
c. At the next workstation location, place the meter on pins 4 and 5.
You should have almost no resistance. A good rule of thumb is 1
ohm for every 25 feet of network cable. If there is 400 feet of cable
to the Master, then there should be no more than 16 ohms of
resistance.
d. Try each workstation in turn, checking to see that the resistance
does not change drastically. If the resistance is high, you may have
a poorly crimped pin, or a partial break in the cable itself. If the
resistance is infinite (completely open), then there is a break, or a
broken conductor.
e. By going from one station to the next, you can isolate what
segment of the cable has a problem.
f. When the entire cable has been checked, remove the jumper from
the Master’s connector.
9. Install the hoods on the connectors. Attach the connectors to the
workstations.
The Terminator Switch
After the network is installed, it is usually necessary to cancel out signal
reflections inherent in any cable layout. To do this, flip on the terminator
switch underneath the MASTER and SUBMASTER WORKSTATIONS
ONLY. The terminator switch is on the bottom of the workstation. The ON
position is toward the top of the workstation.
Figure 2.10
Terminator Switch
Note: The terminator switch should be OFF on all workstations except the
MASTER and SUBMASTER. If other terminator switches are on,
indeterminate network conditions will occur.
Communication Cables
The cables used to communicate from the Host computer to the Master or
from a Concentrator to a Sub-Master workstation use either RS-232 or
RS-422 signal standards. The connector pin-out diagrams for all of the
possible workstation configurations are shown in Appendix D.
Step By Step Installation
(cont’d)