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What is PoM or Power over Modbus?

Modbus RTU – how to interconnect Sentera devices

Sentera products share information via Modbus RTU communication. Modbus RTU is a serial communication protocol that uses RS485 technology.
 
The term ‘PoM’ stands for ‘Power over Modbus’. It refers to a technology that both Modbus RTU communication and the 24 VDC power supply for the connected devices are distributed via one single UTP cable (Unshielded Twisted Pair cable). This makes it possible to connect different HVAC sensors, potentiometers and other Sentera devices via one cable. 
 
Some Sentera sensors have classic terminal blocks. In this case a UTP cable with loose wire ends is required. Sentera -M series HVAC sensors can be connected via one simple RJ45 connector. Sentera 24 VDC power supplies are also available with RJ45 connectors.
 
 Sentera PoM cable with RJ45 connector
 
PoM wiring makes wiring more efficient and reduces the risk of wrong connections. Modbus RTU communication offers the advantage of higher cable lengths compared to analogue signals. PoM combines 24 Volt supply voltage and Modbus RTU communication in one UTP cable. That reduces the risk of disturbances and all devices can be connected via one cable.
  

This movie shows how easy it is to crimp an RJ45 connector:
 
video
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