Is an isolator needed if the transmitter is too far away from the DCS room?
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The field pressure transmitter is 1 kilometer away from the control room; it uses shielded cables. Is there much signal attenuation for a 4-20 ma signal? Is it necessary to use an isolator or any other form of compensation?
How many channel signals can a cable generally support without interference between them?
The voltage drop across the cable must ensure that the field transmitter can operate properly; otherwise, the cross-sectional area of the cable should be increased.
For wire diameters greater than 1,5 mm2, 1 km is no problem.
One kilometer isn’t a long distance; the key is that the resistance value of the instrument cable must be within the specified range – if it isn’t, even a few hundred meters won’t suffice