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4) Check that the isometer device is active:
To verify that the isometer is sending data over RS485 and that the wiring is correct the following should be observed on the SA380TX toucscreen.
Main Screen:
Bender CONN DN indicates no connection error.
Additional alarm state changes may also be observed, but not if no fault condition exists.
Real Time Digital Screen:
Use the "Next Unit" button to scroll to digital channels received from the isometer.
This screen is a poor indicator of connection status, as the state of the digital channels depends on the fault condition of the cables under test. Bender CONN DN should be clear.
Real Time Analogue Screen:
Press the "Next Channels" button twice to scroll to the analogue channels received from the isometer.
This should show the present alarm levels, as well as the current resistance to earth reading obtained from the isometer. The value of the Bender Insulation channel must match the value displayed on the isometer display exactly.
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If no RS485 data is visible: Be patient. isometers may take up to 2 minutes to complete a single measurement, therefore it may be up to two minutes before data is visible Check the integrity of the wiring. It could be poorly terminated cable. Check the polarity of the wiring. It is very easy to get the "A" and "B" the wrong way around Check for data on the RS485 bus. Ideally use a serial port on a computer to check for traffic. The baud rate is 9,600 bps. You should a string of numbers being transmitted periodically Check for data on the RS485 bus. Alternatively connect a volt-meter with a rapid response across the A and B links. a brief spike in voltage should be observed when data is present on the bus, Bear in mind the low update rate, and that the RS485 message only lasts a few milliseconds. |
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