rotork Pakscan IIS, Техническое руководство

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Publication S130E Issue 1.0
Pakscan IIS Technical Manual
In most systems communication errors will occur due to interference from associated plant. The main thing is
that they should be relatively infrequent. The system performance can be monitored by examining the counter,
waiting a short while, and rechecking the value. The counter only refreshes when the screen is first loaded, so
to see changes it is necessary to leave and return to the selected screen. There should not be a significant
change in the error count. If there is then it is an indication that there is a problem on the loop, this may be a
cable fault (low resistance to earth for example), or that the loop is being run too fast for the cable fitted, or
that a particular field unit is not functioning correctly.
If line errors cause problems the most likely causes are:
(1) - twisted pair screen not earthed at master station
(2) - twisted pair screen earthed at both ends
(3) - twisted pair screen broken/not linked at field unit(s)
(4) - line resistance too great
(5) - line capacitance too great
(6) - incorrectly adjusted loop voltages
10.4.2 Checking Host Communications
If there are no communications between host and master station, check the diagnostic screen's 'Rx' and 'Tx'
flags. Check the port setups at each end (baud rate, parity, etc.), and the cable connections between the two.
These checks will usually succeed in getting messages going to and fro.
To assist in verifying that host communications are functioning correctly a simple screen is available that
shows Modbus messages that have been received, and the validity of the messages. The 'Port Diagnostic
Display' is available for both Port 1 and Port 2 (see section 8.4.2 l). The last Modbus message received is
displayed and the number of messages together with an error count. Pressing the 'Load' button will update the
screen to the latest information. Successive screen interrogations will reveal all the modbus messages being
sent to the master station. Pressing the ‘Clear’ button will reset the message counter to zero.
10.5 Final Checks
When the system is operating correctly use the following list to verify that everything has been covered.
ACTION DONE
a) Communication with every field unit and its operation has been verified ................
b) All jumper links on the master station are correct and the station Address set ................
c) The loop parameters for highest address, baud rate and doubling are set ................
d) Port 1 and Port 2 communications have been set, ESD actions have been set ................
e) The Security PIN and Access level has been set, tag names are entered ................
f) The Comms Fail count for each field unit has been set to zero ................
g) The Port 1 and Port 2 Exception Message count has been set to zero ................
h) The Clock has been set to the correct time and date ................
i) All the covers are replaced ................
j) The documentation record is complete ................