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Maxim > Design Support > Technical Documents > Reference Schematics > A/D and D/A Conversion/Sampling Circuits > APP 5610
Maxim > Design Support > Technical Documents > Reference Schematics > Amplifiers > APP 5610
Maxim > Design Support > Technical Documents > Reference Schematics > Interface Circuits > APP 5610
Keywords: 4-20mA current loop transmitter, industrial process control, industrial applications, automation, smart sensors, PLC,
HART modem
REFERENCE SCHEMATIC 5610
High-Performance, High-Accuracy 4-20mA Current-Loop
Transmitter Meets Toughest Industrial Requirements
By: Yuriy Kurtsevoy, Strategic Applications Enginee
Stuart Smith, Product Definer
Dec 17, 2013
Abstract:
This reference design
shows how to develop a high-performance, high-voltage 2- or 3-wire 4–20mA current-loop
transmitter suitable for industrial process control and smart sensors. Error analysis and overtemperature characterization data as
well as hardware design and software are provided.
A similar version of this article appeared in the August 2013 issue of EE Times China and the November 2013 issues of EDN
Europe and ELEKTRONIK.
Associated 4–20mA transmitter design calculator (XLSX) is available for download.
Introduction
The 4–20mA current loop has been widely used as an analog communication interface in industrial applications. It facilitates
transmission of data from remote sensors over a twisted-pair cable to a programmable logic controller (PLC) in a control center.
Simplicity, reliable data transfer over long distances, good noise immunity, and low implementation cost make this interface well
suited for long-term industrial process control and automated monitoring of remote objects.
To no one’s surprise, industry is evolving just like all electronic applications today. It has more stringent demands. There are new
requirements for higher accuracy, lower power, reliable operation over an extended -40°C to +105°C industrial temperature
range, added security and system protection, and implementation of the digital Highway Addressable Remote Transducer
(HART
®
) protocol. Collectively, these requirements make the design of today’s 4–20mA current loop quite challenging.
This reference design explains how to develop a 4–20mA current-loop transmitter, analyze its performance, and select the
components that meet rigorous industrial requirements. Test data for error analysis, overtemperature characterization data,
schematics, and analysis software are provided.
Principles of Operation and Key Design Parameters
We start by focusing on the new reference design. The block diagram in Figure 1 shows the high-performance, low-power, 4–
20mA current-loop transmitter that reduces component count and yields the best results for price versus performance.
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