Explain about 4 wire instrument concept & tell about its
wiring fron sensor in Field to PLC panel.Explain with an
example?

Answer Posted / hadi

4 wire connection sensor have two methods:
1-sensor's power is provided from card
2-sensor's power is provided from field
in first method the power is +24VDC and the current limit
exist but in second method the power is every thing and
transmitter feed from external power supply.
in two methods the signal lines and power lines are different.

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