envea VIEW 370, Руководство пользователя

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8 Maintenance VIEW 370/373
38
(PC-000855-MA Issue 6, December 2021)
ENVEA UK Ltd
8.5 Troubleshooting
8.5.1 Communication Failure
The control unit can support many sensors and devices that may be spread over
a wide area of plant. It is, therefore, essential to be methodical in the approach
to locating the cause of communications problems. If you cannot get the complete
network to communicate, it is best to disconnect some of the sensors and add
them in one by one to see where the problem occurs.
Diagnostics
• Use the control unit to check the Sensor Comms mode (refer to the
B
ASIC
S
YSTEM
S
ETUP
on page 20).
• Run AutoDetect and note which devices fail to be detected. If existing
devices have stopped communicating, this will show up as:
• A ‘ No Response ’ alarm at the bottom of the screen
• A flashing red LED
• On the QA/Self-Tests page, the Comms Check shows ‘ No Response ’.
If the problem exists with only one or two devices, visit those devices and check:
• Cable connections
• Comms DIP switch settings
• Network address DIP switch settings.
NOTE
To prevent bus conflicts, each device must have a unique address.
Devices must not use address ‘0’.
8.5.2 Checking Network Spurs
Where spurs are used, the internal yellow and green LEDs may be used as a
service guide. The devices communicate by a set of query-response cycles. If
either LED is stuck ON, this indicates a wiring error or possibly an incorrectly set
bus termination switch at some point in the network.
8.5.3 Power Loss
The sensors are powered from the control unit (24V). With long cable runs, there
will be voltage drop along the cable. If the voltage drop is too large (<18V), the
sensor will not communicate correctly. Check the voltage at each sensor with a
multimeter between the 24V and 0V pins.
NOTE
If the voltage is too low at any sensor in the network, this may
cause communication problems in the whole network. Correct
voltage problems by adding a PSU Repeater to the network. If you
are already using a PSU Repeater, check it has not been powered
OFF.
8.5.4 Frozen Readings
If a sensor reading is not updating, then
1. If there is also a ‘ No Response ’ alarm, then you have either: