Current signals are often used in sensors because the current response is usually more linear than the voltage response. Current signals also typically provide a low impedance for sensors, with the benefit of better immunity to noise. One practical consideration is that current signals can extend much further than voltage signals, allowing robust signal wire lengths of up to 1, meters.
Most mA loops use two wires, but there are also three- and four-wire configurations that separate a positive supply from the output connection. The advantage of using a mA signal is that Current signals do not have this problem.
The current can induce a magnetic field and cross talk to parallel lines. One should use twisted wire and keep it distant from other communication lines.
Skip to content Any process parameter such as Temperature, Pressure, Flow, Density is sensed, measured by a sensor and is converted to an electrical signal in the form of voltage. Most of the applications use mA signal instead of mA or V, or V. Calculate percentage of signal corresponding to mA signal Measured Value -. Advantages : It is more robust against electromagnetic interference.
Disadvantages: The current can induce a magnetic field and cross talk to parallel lines. The voltage drop will affect the reading. But the device it drives, the positioner, uses 3. If the range zero were truly zero mA, then there would be no loop current or too little loop current at 1mA or 2mA to power a field instrument. Then field instruments would have to 3-wire or 4-wire devices, with all the attendant cost of additional wiring. With a milliameter inserted into the circuit or across a diode in the circuit.
Lots of resistor values, from 1 ohm to ohms, have been used ohms is the most common. Recommended Articles. More Articles. Instrumentation Design.
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