SCC Modules in SCC-68 RailHardware: SCC, SCC>>Modules
Problem: When I try to read an analog input signal through an SCC module in a SCC-68 terminal block, the signal appears to rail. For example, when trying to read a 0-20mA current through a SCC-CI20 module, it always reads 20mA, regardless of the input I provide it. I confirmed that I have made the proper terminal connections for my signal and confirmed that the SCC-68 has the necessary power. Why can I not read a valid input through my analog input SCC module? Solution: For analog input SCC modules, the SCC-68 requires that AI SENSE (Pin 62) be connected to AI GND (Pin 67) for proper grounding. Neglecting to connect these two terminals can result in an analog input signal measurement railing. The following figure illustrates this connection:
After properly grounding the SCC module via the above connection, you will begin reading accurate measurements. Related Links: Products & Services: SCC -- Portable, Low-Cost Signal Conditioning Products & Services: NI SCC-68 Product Manuals: SCC-68 User Guide and Specifications KnowledgeBase 42MK86KG: What SCC Modules are Supported by the SCC-68? Developer Zone Tutorial: Field Wiring and Noise Considerations for Analog Signals Attachments: 
Report Date: 03/30/2006 Last Updated: 07/14/2008 Document ID: 3VTGAB46 |
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