The loop is nothing but the wiring which carries the signal from transmitter to receiver and then back to it.īut, even 4-20 mA has some demerits. The transducer provides the physical signal and the transmitter converts this into an electrical signal.Ī power source is used to produce the required electrical signal and drive the current in the circuit. The sensor consists of a transducer and transmitter. Now, let us consider the second image below. If you remember, according to Ohm’s law, V=I*R. However, current remains the same in the whole circuit. Through current passing across each load, voltage drop occurs each of them and will vary according to the resistance available. The power supply will give the voltage required to drive the current loop. The circuit consists of a power supply and two loads. Now, let us understand first how a current loop flows in an analog circuit by simple Ohm’s law. This problem does not occur in current transmitters. Current transmitters are less prone to electromagnetic interference.Īlso, if the distances are long for connection, resistances increase with distance which causes a larger voltage drop. A voltage transmitter will mostly require a 4-wire connection.īut, a current transmitter can be configured with only 2 wires in connection. The most important advantage of the current signal over voltage signal is wiring. Of these, the widely popular one that is used is the 4-20 mA type one. The two most used types of analog signals in instrumentation are 0-10 V and 4-20 mA. In this post, we will see the use of isolators and barriers in an electrical panel.
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