Troubleshooting device or segment errors

The device's Resource and Transducer blocks are good starting places for diagnosing device problems. Open DeltaV Explorer, select the Resource or Transducer block for the device, and view the status and mode. The status should be clear, with no errors and the mode should be AUTO. Refer to the device documentation for more information.

Next use DeltaV Diagnostics.

• Click Start → DeltaV Operator → Diagnostics to open DeltaV Diagnostics. Typically, integrity problems originate below the node and then "bubble up" to the node level. In DeltaV Diagnostics, integrity problems are indicated by the overlay. Expand the Control Network hierarchy in the left pane of DeltaV Diagnostics and look for any instances of the overlaid over a node or subsystem.
• Look for a controller with this overlay and if you find one:
  • Expand the controller hierarchy until you find the root cause of the problem. The problem could be improper wiring causing noise if:
    • There is a communication error on the device.
    • The H1 card port shows bad integrity.

Diagnose the problem with an oscilloscope:

• Connect an oscilloscope to the segment across the positive and negative leads.
• Take a snapshot of the signal to determine the noise level. The actual signal amplitude should be between 0.5 and 0.9 V peak to peak. The noise should be less than 75 mV peak to peak.
• Take the noise measurement at several different points on the segment such as the H1 card, the power supply, the field junction box, and at any of the field devices. If the signal magnitude and noise exceed the ranges listed above, fix the field wiring and cable shielding.

Fix the field wiring by:

• Grounding the shield only in one place, preferably the DeltaV system cabinet. Use shielded, twisted-pair cable.
• Cutting and taping the shield inside the instrument housing to prevent the shield from contacting the instrument housing and possibly causing a ground loop.
• Wiring all spurs in parallel (individually or as a group in a junction box, including the shield). If the wiring between the H1 card and the power supply uses untwisted, unshielded power cable, excessive noise can occur.
• Continuingthe twisted, shielded pair all the way back to the H1 card and ground the shield at the ground bus bar on the 8-wide I/O carrier.
• Checking all junction boxes and tape or tie into place any exposed shielding or drain to ensure that they do not become grounded to the junction box.