Fig 65
Measuring the voltage across the end of the loop for correct function this should be over 15V (usually
over 18V). If the panel is left in this state, the end devices will go into fault. The faulty device should
be one of the active devices.
Short Circuit start or end of a loop.
There is a short at the start or end of the mentioned loop. The fault can only be on the panel. The
first/last device or the wiring in between the panel and the device. This prevents the loop driver from
functioning and must be fixed in order to auto-learn the panel. Common causes would be: -
Either the first or last device is wired incorrectly.
The loop connections into the panel are wrong.
Something is shorting on the PCB.
No device between the last Spur Isolator and the panel
If the initial loop test didn't show a short across the loop power down the panel and remove the loop
driver.
Measure the resistance across the loop using the appropriate terminals, If this is still in the Mohm
region change the loop driver card. If this is short circuit recheck the loop by disconnecting the loop
and measuring.
If this is Mohms change the motherboard.
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