I am facing an issue with 7 Allen Bradley 1756-IT6 thermocouple input cards, all using J type thermocouple inputs along with cold junction sensors. One of the cards is providing accurate readings, while the other 6 cards are consistently showing a 110-degree variance. Uncertain whether the cards are faulty or require calibration, I attempted to calibrate them as per the manual instructions. However, I encountered an error message stating "The module cannot be found. The path specified was invalid," hindering the calibration process. Despite ensuring proper settings for major and minor revisions, I am unable to resolve the issue. Notably, all cards function correctly with milivolt inputs instead of thermocouples, adding to my confusion. Your assistance is greatly appreciated.
Welcome to the forum! It appears that the issue you are facing pertains to configuration settings. Can you please provide a photo showcasing how you have set up your cards? This will help us better understand and assist you.
If you replace a "Bad" card with a "Good" card, the accuracy of the "Good" readings may still be reliable. If not, there may be a configuration problem or a wiring issue with the "Bad" cards. You have the option to hot-swap (if safe for your operations) using Logix.
Thank you for your assistance. My current setup includes the power supply, the 1756-l55 processor in slot 0, and the 1756-it6i/a in slot 1. My goal is to test all the inputs on the card. Despite setting the properties under configuration the same for both good and bad cards, and using the same testing program and wiring connector for all cards, the issue does not seem to be related to configuration.
The image shows the card in slot 9, but I experimented with various slots. I tested different configurations for optimal performance.
Calibrating at 110 degrees involves more than just a simple adjustment. It is essential to thoroughly inspect the wiring to ensure correct polarity throughout the entire system, not just at the card. For a helpful guide on thermocouple color codes, visit Omega's website: http://www.omega.com/techref/thermcolorcodes.html.
It's apparent you've made several attempts to diagnose and resolve the issue yourself, which is commendable. The error message stating "The module cannot be found. The path specified was invalid" suggests a possible communication error rather than a calibration issue. Have you tried checking the ControlLogix chassis? Sometimes, a loose backplane or improper seating of your card can cause this sort of anomaly. I would also suggest cross-checking the terminal block connections. If the cards function correctly with millivolt inputs, it doesn’t seem like the cards are faulty. Also, consider revisiting the firmware, ensure it's updated and compatible with your module. I hope this helps!
It sounds like a frustrating situation. One thing to consider is the integrity of your thermocouples and cold junction compensation (CJC) sensors. There might be a compatibility issue with the CJC sensors and the cards. Also, just to confirm, you're not exceeding the cable length for J type thermocouples, right? Regarding the error message, it could be a software issue. Are you using the correct version of RSLogix 5000? Make sure all software updates have been done. Indeed, the issue with mV inputs is puzzling, this inconsistency definitely points towards an input or setup problem.
It sounds like a frustrating situation you’re dealing with! Given that one card is accurate and the others show such a large discrepancy, it might be worth checking the wiring and connections for the thermocouples themselves first. Sometimes, improper connections can lead to erratic readings. Also, since you’re able to get good readings with the millivolt inputs, it suggests that the cards are generally working. Have you tried swapping the thermocouples between the functioning card and the ones with the variance to see if the problem follows the thermocouples or stays with the cards? That could provide more insight into whether it’s a calibration issue or something specific to the faulty cards.
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Answer: Answer: Inconsistent readings on multiple cards could indicate a calibration issue or potential faults within the cards themselves.
Answer: Answer: The error message during calibration may point to incorrect settings or potential issues with the calibration process.
Answer: Answer: Correct functionality with milivolt inputs but not with thermocouples could indicate specific issues related to the thermocouple inputs or their calibration settings.
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