1. task is to measure 16 different 4-20mA transmitter outputs without shorting each other ground reference.
Receiver side controller is microcontroller is powered by 3.3V.
2. I have attached a pdf, having two different circuits. First page shows a circuit in which transmitter has been individually enabled by CD4067(16:1 mux demux). 150 ohm resistor cmake 150x20mA = 3V. First both mux are inhibited then combination is formed & output is taken. Its equivalent diagram is shown in rectangular box. CD4067 has 125 Rdson & 25mA max current capability. Problem in this circuit that on return path the ground is different, a additional 125ohm is added between two. Although much current will not flow from it, but it would create offset.
3. Second page, uses only one 150 ohm resistor. Its equivalent is also shown. Although groung problem is corrected in it but it allow entre 20mA to flow from CD4067, & it has max specified limt as 25mA. I dont know how safe it would be here?
4. Is there any better method to do where there is isolation also?
Receiver side controller is microcontroller is powered by 3.3V.
2. I have attached a pdf, having two different circuits. First page shows a circuit in which transmitter has been individually enabled by CD4067(16:1 mux demux). 150 ohm resistor cmake 150x20mA = 3V. First both mux are inhibited then combination is formed & output is taken. Its equivalent diagram is shown in rectangular box. CD4067 has 125 Rdson & 25mA max current capability. Problem in this circuit that on return path the ground is different, a additional 125ohm is added between two. Although much current will not flow from it, but it would create offset.
3. Second page, uses only one 150 ohm resistor. Its equivalent is also shown. Although groung problem is corrected in it but it allow entre 20mA to flow from CD4067, & it has max specified limt as 25mA. I dont know how safe it would be here?
4. Is there any better method to do where there is isolation also?
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