![]() The voltage drop in the wire is proportional to the length of the wire. The voltage signals transmitted over long distances encounter voltage drops due to the resistance of the wire. If voltage signals are used instead of current signals, they become prone to losses. In industrial process control and instrumentation systems, accuracy is an important factor. ![]() Why Is the Signaling Range Set to 4-20 mA? Most process instrument manufacturers stick to the standard 4-20 mA range to maintain compatibility between field instruments, control systems, and sensor signals. One of the most widely used standards from ISA is ANSI/ISA-50.00.01, referred to as “Compatibility of Analog Signals for Electronic Industrial Process Instruments.” According to this standard, 4-20 mA is specified as the signaling range for analog data transmission of instrumentation, control, and other industrial electronic device signals. The current range is maintained within 4-20 mA to meet the requirements specified by the International Society of Automation (ISA). Most of these electronic process instruments utilize the 4-20 mA current loop bus. The Compatibility of Analog Signals for Electronic Process Instrumentsĭifferent instruments, sensors, actuators, valves, and process control systems are employed to enable the safe, reliable, and uninterrupted operation of systems. In this article, we will explore the 4-20 mA current loop and its receiver circuit. Usually, a 4-20 mA receiver circuit is incorporated in industrial systems to receive the current output from sensors or field instruments. Because of the various characteristics of the 4-20 mA current loop, most sensors utilized in industries are designed for an output of 4-20 mA to indicate their measurements. The biggest advantage of the 4-20 mA current loop is its non-degradation of current value over long distances. As the name suggests, the minimum and maximum values of the current in the bus are 4 mA and 20 mA, respectively. The 4-20 mA current loop bus is implemented in electronic control systems for signal transmission and process sensing. As one of the most commonly used standards for communication buses in industrial systems, the analog 4-20 mA current loop makes this possible. It is critical that industrial systems are able to exchange information about environmental variables, sensor outputs, and control signals. The analog 4-20 mA current loop is one of the most commonly used standards for communication buses ![]() The most effective current to voltage conversion method is to insert a precision shunt resistor across the terminals of the 4-20 mA receiver circuit. The receiver circuit is designed to measure or read the regulated current flowing in a 4-20 mA loop. Most industrial electronic process instruments utilize the 4-20 mA current loop bus.
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