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Technologies - 4-20mA Current Loop

4–20 mA Current Loops are commonly used for electronic sensor signals.

With the two values of 4 & 20 mA representing 0–100% of the range of the measured signal. 

Current loops are used both for carrying sensor information from field instrumentation to a measurement device, and carrying control signals back to an output device, such as a valve or actuator.

The advantages of a current loop are:
•    The loop can often power the field device, with power supplied by the controller, removing need for additional power cabling.
•    The accuracy of the signal is not affected by voltage drop.
•    It has high noise immunity as it is a low impedance circuit, normally on a twisted pair.
•    It is self-monitoring; currents less than 4 mA or more than 20 mA are taken to indicate a fault, or a cable break. 
•    It can be carried over long distances.
•    In line displays can be inserted and powered by the current loop.
•    Easy conversion to voltage using resistors.

4-20mA current loops are a very popular signal type in industrial environments. Field instruments and output devices can be sourced to suit many applications, enabling complex and powerful solutions to be deployed. 

The IoT Hub 4G is compatible with 4-20mA input and output cards, allowing data to be captured from many 4-20mA current loop devices and visualised on the Go Monitor Cloud Platform.


For existing systems, solutions using signal conditioners and signal isolators allow the IoT Hub 4G to interface with pre-existing 4-20mA current loops, without disrupting the existing circuit or existing functionality. The current loop signal is simply ‘listened to’, and then brought into the Cloud Platform for use in dashboards, insights or alarming.

The IoT Hub 4G is capable of capturing data from 500+ analogue sensors signals, along with a mixture of other signal types and technologies such as Modbus RS-485, Modbus TCP/IP, 0-10V inputs, Temperature Sensors and many others.   

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