There are issues with the communication of the differential pressure transmitter 475 regarding temperature and pressure compensation
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There is an A+K balanced flow meter on site; the manufacturer supplied it along with Rosemount differential pressure transmitters from Beijing Yuandong. After proper wiring to the DCS system (which is from Zhejiang University Zhongkong), the display worked normally. The meter has temperature and pressure compensation functions, but I’m not sure how this compensation is configured. When trying to connect the device using a 475 handheld communicator from the DCS cabinet, it indicated that the device could not be found. Question 1: The control personnel believe that the loop resistance is insufficient. But I had never encountered such a phenomenon before, because Emerson’s meter and Emerson’s handheld controller cannot communicate; only when they are connected in series do I need to add a 250-ohm resistor. Question 2: Currently, I’m wondering if it’s related to the polling address, as this sensor has temperature and pressure compensation – could there be multiple devices in one polling address circuit?
Just connect a resistor in series
If the transmitter is powered by a flow meter, a resistor is required
But I basically always needed to use a 250-ohm resistor when working with single-school setups; with DCS, I’ve never seen a situation where the 475 model couldn’t be connected to the meter due to insufficient loop resistance
But I rarely see situations where a 250-ohm load is required; this only occurs when there is a single school. In such cases, connecting to the DCS usually works fine. Is it due to problems with the DCS system in the control center? I had never seen a situation where a watch couldn’t be fitted before. After all, Rosemont’s watch is for Emerson’s hand controller
If there are multiple devices with different versions in your circuit, each having its own specific address, then you need to modify the polling menu options; it seems that selecting addresses 0-15 will do. For individual devices, it’s necessary to connect resistors in series – my 375 devices also require resistors in series in order to communicate
The model is 3051SMV, right? This watch does indeed come with built-in temperature and pressure compensation. Then, the image you sent shows the polling address set by the 475 itself. If you can use this 475 to communicate with other types of instruments, then there is no issue with the polling address. Regarding your question, here are a few suggestions. First and simplest, check the issues with the power supply and circuit resistance; try using a different power supply, or have the signal generator provide power, or use a converter to change 220V to 24V. You can also try adding a 250-ohm resistor – under normal circumstances, communication should be established after trying these steps. If communication is still not possible, then either the gauge is broken or the 475 is faulty. I suggest you try communicating with other instruments to see if they are working properly. However, for this type of instrument, after using the 475 communication protocol, it basically loses much of its significance – nothing can be changed; there is specialized software used for detailed configuration.
It might be due to problems with temperature changes if it can’t be connected. Previously, many units in our factory had issues with temperature changes; it seems we bought fake products
The model is 3051CD2A22A1AB4K5M5HR5; I plan to try adding a 250-ohm resistor. It is possible to communicate with this device using a 475 as well as with other transmitters on site (from Zhejiang University’s Zhongkong company), but only the general menu structure can be viewed. The device itself seems not to be damaged. One day, during configuration and testing, they asked me to provide a signal for circuit testing; later it was found that communication wasn’t possible from my end, so they carried out forced communication from the DCS side
For the gauge of this model you provided, the gauge itself cannot perform compensation; compensation needs to be done at the system level. It’s not the one I mentioned before. If that’s the case, is your power supply supplied directly by the card? It is still powered by a secondary meter, such as a flow integrator or something similar; if it is powered by a secondary meter, there may be issues with communication. I still suggest you replace the power supply and add a resistor.