Wiring of pneumatic cut-off valves and control valves
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Why do pneumatic cut-off valves use a six-wire connection system, while pneumatic control valves use a two-wire system? What do DI/DO, AI/AO correspond to in a DCS?
The input signal for the control valve is a 4-20mA current signal, transmitted over 2 wires； Cut-off valves are generally controlled by solenoid valves, which require 2 wires. Cut-off valves usually need 2 position switches to indicate the valve’s operating state, and these position switches require 3 or 4 wires. DI: Digital input ； DO: Digital output ； AI: Analog input ； AO: Analog output.
Activate the cut-off valve; there are feedback signals via two or three wires, including two DI points and one DO point. Feel free to ask if you have any questions
DO 1: Solenoid valve signal; DI 2: Valve open position, Valve closed position
The answer on floor 4 is not as good as that on floor 2 – how can it be chosen as the best?
The input signal for the control valve is a 4-20mA current signal, transmitted over 2 wires； Cut-off valves are generally controlled by solenoid valves, which require 2 wires. Cut-off valves usually need 2 position switches to indicate the valve’s operating state, and these position switches require 3 or 4 wires. DI: Digital input ； DO: Digital output ； AI: Analog input ； AO: Analog output. Two DI points, one DO point. For the DO point: one for solenoid valve signal, and two for valve position – open and closed. I’ve learned it.*
Can a pneumatic on-off valve with feedback be powered directly by a single 6-core control cable with overall shielding?