Hello, I am looking to read three 4-20mA signals from a DCS (ABB) using a remote 6-channel analog input module with an RS485 Modbus port. When I connect the signals individually, I am able to read the raw count values in my AI module. However, when all three signals are connected simultaneously, none of the signals work in the module. Is there a different method to connect all three signals in a single analog input module? Thank you for any assistance you can provide.
It appears that you require isolation transmitters to ensure optimal signal quality and prevent interference.
Encountering a common mode ground loop issue is a classic scenario in industrial settings. The AI circuits in the AI module may have a ground reference at a different potential compared to the DCS AO ground reference. While connecting a single AO signal may not exceed the AI module's common mode limitation, connecting all three signals can lead to an exceedance. In rare instances, resolving the problem may involve floating the DC (-) of the power supply feeding the AI module. Surprisingly, in one instance, establishing a ground connection between the AI and AO units proved beneficial. Typically, purchasing 4-20mA isolator modules is the recommended solution for such issues.
It sounds like you might be experiencing a grounding issue. Ensure you're not creating a ground loop when connecting all three signals together. An alternative approach could be to use isolation techniques, such as implementing isolated transmitter modules in each 4-20mA signal line to prevent interference. Additionally, check the power supply of your analog input module; it needs to be adequate and stable for all three signals. Lastly, verify the addressing in your Modbus configuration to ensure there's no conflict. Stick with it, good luck!
Hi, it seems like you might be experiencing a signal interference when multiple inputs are connected simultaneously. This is not uncommon for analog input modules. One solution to try if you haven't already is to make sure each of your 4-20mA signals are sourced from independent/individual loop supplies to avoid ground loops. If they share the same power supply, conflicts can arise due to potential differences. Also, remember to consider impedance matching as it can be crucial when dealing with Modbus/RS485. Lastly, ensure you check your wiring and your AI module configuration to cater for multiple inputs. Good luck, and feel free to post any updates or additional questions you may have!
I suspect you might be running into an issue with shared return paths - each 4-20mA loop should have a separate return path to the individual module. If you've bundled them together, it might explain why you're seeing problems when you connect all three simultaneously. I recommend rechecking the wiring connections and ensuring that each signal has its own dedicated return path to the input module. Also, ensure that the module and the DCS have a common ground. If the problem persists, the issue might be within the module itself or the communication interface (RS485/Modbus).
It sounds like you're dealing with a common problem known as "ground loop". When multiple 4-20mA signals share a common ground reference, the voltage potentials might differ, causing unintended current flow between grounds, which can distort your readings. Try isolating your signals if possible, or you could use a signal conditioner module that offers ground loop isolation for each channel. If your module doesn't support this, check with ABB for a compatible one. Remember, always follow the rules for proper grounding to avoid these issues.
It sounds like you're experiencing a common issue with impedance or signal loading when trying to read multiple 4-20mA signals simultaneously. One solution could be to ensure that your analog input module allows for the configuration of input channels correctly, as some modules require specific settings for multiplexing signals. Additionally, you might want to check if your DCS output signals are properly wired in a way that they can operate without interference, such as ensuring that they are not sharing the same ground path. Lastly, using a multichannel resistor and ensuring the input module is set to read multiple signals may help; if you're still having issues, consider consulting the module's manual for any specific limitations or configurations. Good luck!
It sounds like you're dealing with a classic case of signal interference or loading issues when multiple 4-20mA signals are connected at once. Make sure that you're not exceeding the current loop requirements for each channel and check if your module supports simultaneous readings on all channels. Using separate power supplies for each transmitter can help isolate them, and ensure that the module is correctly configured to handle multiple inputs, including scaling and addressing. If the problem persists, it might be worth double-checking your wiring and grounding to eliminate any potential noise issues. Don’t forget to consult the manual for both your DCS and the remote module for any additional configuration settings!
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Answer: - The issue might be related to wiring or signal interference when connecting multiple signals at once. It is important to ensure proper wiring connections and consider signal isolation techniques to prevent interference.
Answer: - One common approach is to use signal isolators or signal splitters to isolate and condition each 4-20mA signal before connecting them to the analog input module. This helps in maintaining signal integrity and prevents cross-talk between the signals.
Answer: - Start by checking the wiring connections for any shorts or incorrect terminations. Verify the power supply requirements for the analog input module and ensure that it can handle the combined current draw of all three signals. Additionally, consider checking the configuration settings of the analog input module to ensure it supports multiple simultaneous inputs.
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