Hello! Can you advise on which system bits I should utilize to detect faults in a specific AI or AO channel, such as a lost 4-20mA loop or a malfunction in a single input? The screenshot provided is from a PLC currently operating without that specific card installed. It seems that Local:8:I.In0Fault is functioning correctly, indicating a fault, whereas Local:8:I.In[0].ChanFault is not, likely due to the absence of the module. I am currently using both but am unsure of the difference between the two. What system bits do you recommend using for this purpose? Thank you.
Inquiring about which fault detection methods are in use? The key advantage of using a 4 - 20mA signal lies in its clear fault indication when values fall outside the normal range of 4mA to 20mA. This range can be adjusted for tolerance errors. Additionally, the 4 - 20mA signal is platform agnostic, making it compatible with comprehensive diagnostic systems from industry leaders like Rockwell and Siemens.
Perhaps my explanation was not clear enough. I have developed a high-quality bit called Temperature_QUAL and an alarm bit called Temperature_F. I use Temperature_QUAL to prevent any issues in the PLC, such as not triggering an alarm if the temperature is low when the signal fails. Instead, I prefer to display an alarm to notify the operator of the abnormal temperature value and allow them to make a decision. I have noticed that system bits are accessible, so I plan to utilize them to create these two BOOLs for each analog input. The second BOOL will serve as the opposite of the first, as I prefer to only set off alarms on screen. I aim to avoid adding additional code to check if each analog input is within the specified range, as this information is already available. I typically follow this approach for Thermocouples (TC) or Resistance Temperature Detectors (RTD) when necessary, but it appears that Rockwell system bits can handle this in this situation. Unfortunately, I will not have the Analog Input/Analog Output modules before commissioning, as we are reusing them, so I am unable to conduct any testing at this time.
The status bit is refreshed from the module memory. If the module is not found, the channel faults are updated by the controller, with all values set to ones. The InXFault is linked to the bits in ChannelFaults. To determine the module's presence and operation, use the GSV function with the parameters Module, XXX_IF8, EntryStatus, and Value16. If the upper 4 bits of Value16 return as 4, it indicates that the module is active; then, you can proceed to check the .ChanFault.
When using the command GSV(Module,XXX_IF8,EntryStatus,Value16), if the upper 4 bits of Value16 return as 4, it indicates that the module is active and operational. To verify, also check for .ChanFault. If the value of AI_AO_01_QUAL in a binary format is above 61440, it signifies a healthy module. Currently, values mostly show as 4096 (2#0001_0000_0000_0000) with a few higher readings. How can I compare 2#0001_0000_0000_0000 to 2#1111_XXXX_XXXX_XXXX accurately? I recall encountering this issue recently but can't remember where. Any guidance on this topic would be greatly appreciated. Thank you.
Is this similar to what we're looking for in terms of the module quality status?
Hey there! You're spot on about the "Local:8:I.In0Fault"; it indicates a general fault in the channel. However, "Local:8:I.In[0].ChanFault" is specifically designed to detect hardware malfunctions within the card (like a fried component). Because your setup doesn't currently have the card installed, that specific fault bit isn't functioning. For detecting issues in the 4-20mA loop, I'd advise using "Local:8:I.In0Fault". Once you've got the card installed, you should utilize the "Local:8:I.In[0].ChanFault" more extensively for specific hardware fault detection. Ultimately, using a combination of both will give a comprehensive picture of AI/AO channel health. Hope this clarifies things!
Hey there! It looks like you're on the right track with your fault detection setup. The key difference between `Local:8:I.In0Fault` and `Local:8:I.In[0].ChanFault` is that the former typically indicates a fault for the entire input channel, while the latter is more specific to individual channels or inputs when the module is fully functional. Since you're dealing with a situation where the module isn't installed, I'd focus on `Local:8:I.In0Fault` for broader fault detection. Once you get the module installed, you might want to explore using both for a more granular view of any issues. Also, consider implementing some logging for these faults; it can really help in diagnosing intermittent issues over time. Hope this helps!
It sounds like you're on the right track! The `Local:8:I.In0Fault` usually indicates a fault condition for that specific input channel, which is great for a quick check if something's wrong with the loop. On the other hand, `Local:8:I.In[0].ChanFault` typically provides more detailed status information about the channel, but as you've noticed, it may not be functional without the module present. For detecting faults in your 4-20mA loop, I recommend sticking with `Local:8:I.In0Fault` since it’s already signaling faults effectively. Once you install the card, you might want to monitor both bits to get the full picture of your input's health!
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Answer: - System bits in RSLogix Designer are used to monitor and detect faults in specific AI (Analog Input) or AO (Analog Output) channels within a PLC system.
Answer: - Local:8:I.In0Fault is a system bit that indicates a fault in a specific input channel, while Local:8:I.In[0].ChanFault is used to detect faults in individual channels of a module. The former is more general, while the latter is channel-specific.
Answer: - By utilizing appropriate system bits like Local:8:I.In0Fault and Local:8:I.In[0].ChanFault, users can effectively monitor and detect faults such as a lost 4-20mA loop or malfunction in a single input channel within the PLC system.
Answer: - For detecting faults in specific AI or AO channels, it is recommended to use system bits like Local:8:I.In0Fault and Local:8:I.In[0].ChanFault based on the requirements and granularity
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