Seeking help regarding RS485 for mass flow meters
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We are using Emerson mass flow meters, which have three types of outputs: 1. 1.4–20 mA, 2. frequency output, and 3. RS485. Initially we used 4–20 mA signals, but now the client wants us to use the RS485 connection for communication. What does that mean? Do we still need to remove the 4-20mA?
RS485 can transmit various parameters such as density and volume, more than 4-20mA can, so most mass flow meters are connected via RS485 lines
These two can coexist. There is no need to remove 4~20mA.
The 485 port of the MICROMOTION 1700 is for testing purposes and should not be connected regularly; the 2700 model has a standard port. MODBUS can provide real-time data, ensuring that the system receives exactly the values contained in the table. Moreover, in reality, the 4-wire connection from MVD’s MICROMOTION core processor to the transmitter consists of one pair for 24VDC supply and one pair of data lines for Modbus communication. There are many applications where people don’t purchase transmitters but only sensors, and the PLC reads the data via MODBUS
How to coexist? Since DCS doesn’t have two input points, which one should be used? 3# 616562409
4~20mA is for AI, while 485 is used for data communication. Most DCS systems can support it; it just requires a 485 card.
Choose 2700 for the transmitter; communication and analog signals can coexist without any issues
These are two separate pathways; they are not contradictory, and it is possible to set two different points on the control panel to distinguish between these two signals!