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Why do I Get Intermittent Errors When I Use a [c]FP-RLY Module?

Hardware: FieldPoint>>Discrete I/O Modules>>FP-RLY-420, Switches>>General-Purpose>>FP-RLY-420, FieldPoint>>Discrete I/O Modules>>FP-RLY-422, Switches>>General-Purpose>>FP-RLY-422, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-420, Switches>>General-Purpose>>cFP-RLY-420, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-421, Switches>>General-Purpose>>cFP-RLY-421, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-422, Switches>>General-Purpose>>cFP-RLY-422, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-423, Switches>>General-Purpose>>cFP-RLY-423, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-425, Switches>>General-Purpose>>cFP-RLY-425

Problem:
I am using a [c]FieldPoint Relay module to switch an inductive load and I get intermittent errors. Most of the time I am able to read and write the channels on the relay module without a problem.

Occasionally I will get one of the following errors:
  • 33027: Addressed module does not exist.
  • 33440: Bad channel status reported for all contained channels: The specified channel is not configured.
  • 33443: Several contained channels reported a bad channel status.
  • 33497: No error message
Also, if I look at the module I see the ready light turn off and then come back on. What could be the cause of this?

Solution:
When switching DC or AC current and you have an inductive load, such as a solenoid, a large voltage potential is generated. The current in the inductive load can not change instantaneously so a large voltage potential is produced. This voltage spike can be enough to cause the relay module to go offline. The amount of time the module is offline varies, but while it is offline you will see the ready light turned off. During this time you may see one of the errors mentioned above. If power has been jumpered between modules using the V and C terminals, the isolation has been defeated and other modules may also go offline.

To prevent the voltage spikes, protective circuitry needs to be added. For more information see the Guidelines for Selecting Contact Protection Circuits section in the Operating Instructions for FP-RLY or the Protecting Contacts for Inductive Loads section in the Operating Instructions for cFP-RLY . Links to the Operating Instructions of the relays modules are given in the Related Links section of this knowledge base.

Related Links:
FP-RLY-420 Operating Instructions
FP-RLY-422 Operating Instructions
cFP-RLY-421 Operating Instructions
cFP-RLY-423 Operating Instructions
cFP-RLY-425 Operating Instructions

Attachments:





Report Date: 06/14/2002
Last Updated: 05/11/2008
Document ID: 2MDAQBOH

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