MTL4546Y safety barrier
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I only work on the system side, and I don’t know much about the circuit from the safety barrier to the valve positioner. I want to know if connecting 1 and 2 to the AO safety barrier represents the power supply of the safety barrier. When I change the OP of the valve on the DCS screen, do I change the resistance in the circuit to change the current? Then through the safety barrier photoelectric isolation through terminals 1 and 2 and then to the electrical conversion circuit, how does the current of this circuit change? Can any expert explain it? Thanks
Generally, the input signal of the valve positioner is mostly two-wire system, and the signal and power supply are shared. So the output from the safety barrier needs to power the positioner. Changing the output value on the DCS software is equivalent to giving the controller a digital quantity, which is converted into an analog quantity through the D/A conversion module. To put it bluntly, it can be understood as changing the resistance value of the channel of the output module.