rotork Pakscan IIS, Техническое руководство

Страница: 65 / 84

Pakscan IIS Technical Manual Issue 1.0
Publication S130E 65
10.4 Diagnostic Information
The master station can provide information via its own display which can help in commissioning and fault
finding.
10.4.1 Loop Configuration
The loop should configure with no loopbacks. If loopbacks are in use (as indicated by the master station status
display), the loop diagnostic screen will indicate which field units have loopbacks asserted. The line fault will
be at or between these units.
A code indicates the reason why loop configuration was last done. This can be useful if the system keeps
doing loop configuration, or fails to configure correctly.
The Port A and Port B LED's may help in indicating what is happening. At start-up, or after a "Reset Loop"
command the master station waits until it is sure that all the field units are in loopback. This time is about 10
seconds at 1200 baud. The Port A LED will come on when there is a complete current circuit. If it does not
come on, there is a break near the Port A end.
The Port A LED then flickers as field units are found and their loopbacks removed. If the loop circuit is
complete, normal scanning will then start and this is indicated by both LED's flickering together. The master
station status will be reported as "Loopbacks Off".
If the loop continuity is incomplete, the master station switches to Port B after it has found all the field units
connected to Port A. The Port B LED then flickers as field units are found there. Having found all the field
units, the loop has to be left with loopbacks on the last-on-circuit field units only. This involves waiting for
loopbacks to come on again, and then removing all of the loopbacks up to the field unit before the loop fault.
The Port A then Port B LED's flicker during this stage. Normal scanning of a broken loop shows up as both
LED's flickering, but not together.
Should the setting of field unit parameters have been carried out incorrectly then the system will identify a
field unit that has an address to high or duplicated with another and eliminate these from the routine data
polling. They are marked in the data base as in error and their individual data screen displays show Comms
Failure and Field Unit Fault.
10.4.2 Loop Communications
On a well-behaved loop, the error rate in communications with each field unit should be very low. The system
should be Reconfigured, and once running successfully with no loopbacks present examine the FCU Map and
Failure Counts screen (as shown in section 8.4.4).
This screen allows verification that the loop wiring follows the desired pattern. The screen shows both the
physical position on the loop and the address of each field unit that is in communication with the master
station. The screen also reveals a counter recording the number of failures in communications with each field
unit. This counter records every error, including those that do not result in a communication failure alarm.
(The alarm is only generated if the communication fails 3 times in succession), and it may be set to zero by the
‘Clear’ button.