Answer / vikram budhiraja

A process variable can be transmitted (as an analog signal) over a pair of wires either as a voltage or a current.

A current (milliamp) analog signal is preferred in control systems over voltage because the current in a loop cannot be different at the generating end and the receiving end regardless of the length of the wire carrying the signal.

On the other hand a voltage signal suffers a drop ( IR loss) depending on the length of the wires carrying the signal resulting in error.

Why we use 4 to 20 mA, (This is International Standard) instaed of this can we use 4-16, or 4-24 or 3- 15 or any other range

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what is stability

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Dear all... I have 1 0-400 duplex type RTD, I connected the A side to the temperature indicator and B side to the PLC panel, but when I have observed then found that The PLC side temp has the variation. and it was distub to other RTD temp also. so what can I do.pls help me

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Witch type cable use for rtd ,why?

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Close loop and open loop.

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