What is the difference between 3-wire and 4-wire connection?
Sensors in an HVAC environment
Sentera -F and -H sensors require a supply voltage of 24 VDC. This type of sensors require a 4-wire connection. They can be connected with a 4-wire electrical cable: 2 wires for the supply voltage and 2 wires for the output signal. The ground connection of the supply voltage and the analogue output are galvanically separated in -F type sensors. That is why they require a 4-wire connection.
4-wire connection reduces the risk of electrical interferences since the supply voltage and the output signal remain completely separated.
Sentera -G sensors require a supply voltage of 24 VAC or 24 VDC. This type of sensors require a 3-wire connection. They can be connected with a 3-wire electrical cable. The ground connection of the supply voltage (V-) is internally connected with the ground of the analogue output (GND). It is called a 'common ground'. This means that only 3 wires are required to connect the supply voltage and the analogue output. Due to this 'common ground', -G and -F type sensors cannot be used together on the same network.
Never connect the common ground of -G type sensors to other devices powered by a DC voltage. Doing so might cause permanent damage to the connected devices.
CO2 sensors with visual and audible alertToo high CO2 concentrations? Sentera CO2 sensors are now available with audible alert. On top of that, the green, yellow and red LED offer a clear, visual indication of the CO2 level. The supply voltage is 230 V or 24 V.>>>
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