Unexpected Relay Behavior on [c]FP-RLY-42x ModulesHardware: Switches>>General-Purpose>>cFP-RLY-420, Switches>>General-Purpose>>cFP-RLY-421, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-422, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-423, Switches>>General-Purpose>>cFP-RLY-425, FieldPoint>>Discrete I/O Modules>>FP-RLY-420, FieldPoint>>Discrete I/O Modules>>FP-RLY-422, Switches>>General-Purpose>>cFP-RLY-420, Switches>>General-Purpose>>cFP-RLY-421, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-422, Compact FieldPoint>>Discrete I/O Modules>>cFP-RLY-423, Switches>>General-Purpose>>cFP-RLY-425
Problem: When I write to one or more channels on a [c]FP-RLY-42x module, other channels on that module or adjacent modules exhibit unexpected behavior. Why is that? Solution: National Instruments recently discovered that if NI [c]FP-RLY-42x FieldPoint or Compact FieldPoint relay modules are exposed to high levels of electromagnetic interference (EMI), relays in the modules or in adjacent modules may open or close unexpectedly. The unexpected relay closure issue was discovered during internal testing and is unlikely in most use cases. National Instruments is expediting upgrades to these products to make them more immune to high levels of EMI. Additional information on how to reserve an upgraded module is included below. Sources of EMI include noise from switching inductive loads (for example, motors and solenoids) and power-supply surges. Proper customer-installed surge suppression on the power supply, and the use of metal oxide varistors (MOVs) or flyback diodes across the load, reduce the effects of EMI and make unexpected relay behavior less likely. Please refer to the operating instructions for your [c]FP-RLY-42x for more information about properly connecting MOVs and flyback diodes. The following link has additional information regarding protecting your relay module when switching inductive loads: KnowledgeBase 4IHG8JLE: Protecting NI Switch Modules when Switching Inductive Loads In addition to unexpected relay closures, high levels of EMI may also cause a [c]FP-RLY-42x to reset unexpectedly. When the module resets, all channels open for 100 ms before returning to the position they were in. You may notice a momentary dimming of the Ready light on the module, or an unconfigured channel error in Measurement & Automation Explorer (MAX), LabVIEW, or other programming environment you are using. Also, the cFP-RLY-425 may report false over temperature errors in MAX, LabVIEW, or another programming environment. This error causes all eight channels to remain in the open position until the module is reset either by hot swapping the module or by rebooting the controller. ACTION REQUIRED – Evaluate the use of these products in your application to ensure that unintentional opening and closing of relays will not create a hazard. Please accept our apology for the inconvenience. National Instruments is committed to your satisfaction and to maintaining your confidence in our products. Related Links: KnowledgeBase 4IHG8JLE: Protecting NI Switch Modules when Switching Inductive Loads Attachments:
Report Date: 01/04/2008 Last Updated: 09/04/2008 Document ID: 4H3DG7SK |
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