Programmable logic controllers (PLCs) use fast, deterministic functions, such as logic, sequencing, timing, counting, and arithmetic algorithms, to control machines and processes. They use analog and digital signals to communicate with end nodes (reading sensors and controlling actuators, for example). Typical methods of communication include current/voltage loops, Fieldbus, and industrial Ethernet protocols.
The industry has a continuing tendency to increase the number of sensor and control nodes in the remote area, causing a corresponding increase in the number of I/O module nodes in the controller—and some distributed control systems (DCS) can handle thousands of nodes. This concentration of nodes brings increased temperature-related challenges, especially for systems that implement the 4-mA to 20-mA loop communications standard.
Perhaps the biggest and most relevant challenge to the system designer is the need for greater efficiency and reduced power consumption, as the inefficiency of existing systems results in wasted power and increased operating costs. This article explains the challenges of designing such systems for greater efficiency and introduces the AD5755, a versatile, 4-channel, 16-bit digital-to-analog converter (DAC) as a more integrated solution to help resolve these issues.
The article is presented as a pdf file, in two parts (no registration required):
Part 1: System overview, and power dissipation concerns, click here.
Part 2: System error checking and diagnostics under fault conditions, flexible output-range programmability, communicating additional information over the 4- to 20-mA current loop, AD5755 complete solution, click here.
About the author
a system applications engineer for the Industrial and Instrumentation segment
at Analog Devices, Inc. (Limerick, Ireland). After working in test-development
engineering at Microsemi, he joined ADI in 1998. He spent three years in an
applications role in Shanghai. He graduated in 1995 from the University of
Limerick, Ireland, with a bachelor's degree in electronic engineering.
Fortunately for circuit designers, a new tool is available that can simplify the process of identifying the ESD suppression device best suited to an application, which makes it far easier to incorporate circuit protection earlier in the board planning process. The Littelfuse iDesign™ Online Simulation and Product Selection Tool
. I received a very good reader question from my last blog post regarding the various parameters that are reported by the tool. Let’s take a look at an example and explore the parameters that are returned. In this example we will look at the AD9643-250.
Managing system thermal performance is critical in today’s electronic systems if you are to maximize performance and the user experience. As systems grow more powerful, and in many cases smaller in size, managing the thermal profile has become an ever-increasing challenge. Monitoring the current provides a leading indicator to potential thermal issues.
In blog number 3, we are going to divert a little from our normal trend of evaluating power supply design and simulation tools. Instead, we are going to look into power management tools that are online.