S7-200 communicates with Modbus power meters using ModBus
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How can an S7-200 communicate with Modbus power meters via ModBus, and then communicate with Viwin touchscreens?
First, determine which one is the master station and which one is the slave station
It’s best to buy a 224 or 226, as that way you’ll have two communication ports. One communicates with the electricity meter, and the other communicates with the touch screen.
Typically, in MODBUS communication, the instruments act as MODBUS slaves while the touch screen functions as the MODBUS master; there is only one master on a single MODBUS network. The PLC is located in between; if it’s an S7-200, the 224XP or 226 model is recommended. These models have two serial ports – one for the touch screen and one for the instruments. Note that the distance between the instruments and the PLC should be less than 1 km.