A Simple Microcontroller-Based 4-20 mA Current Loop Receiver for Sensors with Current Transmitters

Abstract

A current loop receiver system based on a microcontroller has been developed. The current loop receiver system can serve 8 gas sensors with 4-20 mA outputs, which are handled by employing a multiplexer. The data acquisition of the system is composed of a common operational amplifier-based current loop receiver, a CD4051 multiplexer, an ADS7822 serial analog to digital converter (ADC), and an AT89S52 microcontroller. The measured gas concentration is displayed on the 7-segments or transmitted to a personal computer via the RS232 serial communication to be processed by the Microsoft Excel. Additional functions such as gas concentration level warning and error code display are also provi ded.

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“…The operation of the 4 to 20 mA loop is straightforward: a sensor's output voltage is first converted to a proportional current, with 4 mA representing the sensor's zero-level output, and 20 mA representing the sensor's full-scale output (Surachman et al, 2011).…”