Need help with Emerson mass flow meters?
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In my flow monitoring system, there are three Emerson mass flow meters that share one 485 communication bus; they are connected to a 485 communication card from Zhejiang University’s Control Systems Department. Previously, the display of data on these three flow meters, both on-site and remotely, was normal； Today, this situation occurred: the data from the farthest location was significantly delayed by about 1 minute compared to the on-site data (in other words, there was no traffic data shown at the on-site site, while the data on the remote monitoring interface continued to be displayed; it stopped after 1 minute) ； Also, when there is traffic at the site, the remotely transmitted data takes 1 minute to appear), and the changes in the remotely transmitted data are slow; meanwhile, the two other displays work normally. I asked Emerson’s supplier, and they said it might be a problem on the side of Zhejiang University’s Zhongkong. But the other 2 units are showing normal. I’m completely confused; please help analyze it for me. Thanks first!
Go to the site and try using a signal generator; if it still doesn’t work, try it at the indoor terminal block. If that still doesn’t resolve the issue, then there is a problem with the system channels
It is recommended to check whether there are any issues with the transmitter output of the flow meter; next, examine the communication module of the central control system and determine whether the computer configuration is sufficient.
Method for determining problems: First, communicate with the Emerson mass flow meter on-site to determine whether it is functioning properly. Second, communicate with the control room to check if everything is normal. This situation is generally not a problem with the mass flow meter. It’s a system issue.
What the people upstairs said is correct; problems usually arise from either the field instruments or the central control system. You can use a laptop for testing – install the MODSCAN and MODSIM software on it, and use a USB-to-485 converter to connect to the 485 communication network. MODSCAN acts as a simulation of the upper-level computer, while MODSIM simulates the lower-level computer. Once you understand the protocols used by the mass flow meter and the central control system, you can use the laptop to replace the central control system or to replace the flow meter itself for testing purposes.
The problem is solved. There are no issues with the instruments on site or the central control system. The problem arose from insulation damage occurring before the farthest signal lines were connected to the bus; after the heavy rains in the previous two days, those farthest signal lines were unable to transmit data. We used a megohmmeter for inspection and found that the signal wire was broken. I pulled a new signal cable, and that fixed it. Thank you all for your concern.
This issue is quite easy to resolve
The lag indicates that the flowmeter signal is useful. It’s better to focus on checking the system. .