Issues related to attenuation when 4-20ma signals are transmitted to DCS
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I’d appreciate some advice…… 1. For example, in the case of the current signal from a motor (powered externally), since the signal is transmitted as a 4-20 mA current signal, theoretically, no matter how much resistance there is in the wiring, it shouldn’t affect the value that is sent to the DCS. Does that mean the distance over which this signal can be transmitted can be infinitely large? 2. For example, in the case of pressure transmitters (with internal power supply), since the DCS provides a 24V power supply, if the wiring is too long and the resistance is too high, it can result in inaccurate signals being sent from the transmitter to the DCS. But isn’t this caused by attenuation in the computer cables? Is that the reason? @1111111
Discussion is welcome{:3_51:}
What does it indicate if there is signal interference from the 4-20ma current signals of the DCS in the control room affecting our control equipment?
The maximum length at which a cable can be installed is directly related to its load capacity (the higher the load capacity, the greater the length over which the cable can be installed). The load capacity refers to the maximum loop resistance at which a circuit can operate stably. In each circuit, the impedance of each component is fixed at the time of manufacturing; therefore, the actual loop resistance is primarily determined by the resistance R of the cable itself. This, in turn, determines the cross-sectional size of the signal cable as well as its maximum installation length.