Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 92)

92 Publication 1753-UM001C-EN-P - March 2010
Chapter 8 Wire and Configure the 1753-IB16XOB8 Module
Line Monitoring with Reduced Voltage for Resistive, Capacitive
Loads
For line monitoring, a 10V signal is switched on in the output circuit
for the duration of the monitoring time. This kind of line monitoring is
designed for resistive or resistive-capacitive loads. There is no
short-circuit detection for these types of loads.
To configure this type of line monitoring:
•
set a DO.LSLB period and DO.LSLB time.
•
set the output DO[xx].2-pole signal to 1 (TRUE).
•
set the output DO[xx].LSLB monitoring signal to 1 (TRUE).
•
set the output DO[xx].LS monitoring with reduced voltage signal
to 1 (TRUE).
See Required Signals for Line Monitoring on page 93 .
Period and Monitoring Times
You must set a period and monitoring time for line control. These
configured times affect all channels that are set for line monitoring.
During monitoring time, readbacks occur at intervals of 1 ms. If no
errors occur, the output is set per the application program.
ATTENTION
During the 10V test to detect a line break, DO+ is at 24V and
DO- is at 14V. If DO- is shorted to 0V DC, then there is 24V at
the output for the duration of the monitoring time, which could
turn on the actuator.
During line monitoring time, a 10V signal is impressed at the
load (relay, actuator). This reduced voltage level (10V) of line
monitoring, is normally not enough to switch the load.
ATTENTION
The duration of monitoring time adds to the cycle time.
TIP
There are 4 tests during the LSLB test period (DO.LSLBperiod).
In principle, this means that there will be a test every 1/4 of the
period. So if the period is 1 second, there will be a test every
250 ms. If the LSLB time duration (DO.LSLB time) is 20 ms, there
will be 230 ms between 20 ms tests.