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Question
Basic 4 to 20ma circuit with plc for power, level transmitter, to analog input card. Were in this circuit can I put a chart recorder and get a full 4 to 20 signal and not just half of the signal.Or what should I do. The chart recorder is 4 to 20 acceptable. I only get half of the signal when connecting between transmitter and card.

Answer
The three loop devices (level transmitter, analog input card, recorder) must all be wired in series. Typical loop-powered devices for use in a 4-20 mA loop (i.e. the input card and the recorder) have a 250 ohms resistor in the loop, and they measure 1 to 5 volts that develops across the resistor.  So, if you are using two such devices in the loop, they are adding 500 ohms.  The recorder may have a specified voltage drop in addition to that.  The amount of loop resistance that your level transmitter can drive depends on its specification and on the power supply voltage.  So, assuming that your devices are all connected in series, you may need to increase the power supply voltage.  If that is not possible, then a loop repeater may be installed.  That will receive its own power, while inserting only a minimal loop resistance, and then repeat the loop current with a greater voltage capability to drive your recorder.  It will be wired in series into the loop with the transmitter and input card, and its output will drive the recorder.

But maybe you wired the analog input and recorder in parallel?  If so, change that to a series connection.

Hope this helps!

Dave

Electrical Engineering

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Dave Nyce

Expertise

I have been an electronics engineer for many years. I can answer questions on analog and digital circuits and my specialty is sensors.

Experience

I am the inventor on 27 US patents, and also some foreign ones. Developed sensors for many years. Licensed private pilot (airplane and rotorcraft), have HAM radio license. I'm not an expert in computer networking.

Organizations
AAAS, Certified Control Engineer, (former UL Advisor for Intrinsic Safety), Benefactor member of NRA. Life member of the following: Experimental Aircraft Assoc., US Parachute Assoc., National Trapper's Assoc., Apex Masonic Lodge #584, Scottish Rite of Raleigh, NC, Academy of Model Aeronautics, Grass Roots North Carolina, NC Rifle & Pistol Assoc. Member of the following: Aircraft Owners & Pilots Assoc., US Hang Gliding & Paragliding Assoc., Tripoli Rocketry Assoc., Apex Historical Society, The Planetary Society, USA Volleyball, Shriners of North America, York Rite Masons, National Space Society, Benevolent and Protective Order of Elks, and the Precision Aerobatics Model Pilots' Assoc.

Publications
Books: "Magnetic Displacement Sensors" section in: Measurement, Instrumentation, and Sensors Handbook, CRC Press, 1999. ISBN 0-8493-8347-1; "Magnetostrictive Sensors", "Hall Effect Position Transducers", & "Strain Gage Accelerometers" in: Instrumentation and Control, a Mechatronics Handbook, John Wiley & Sons, Inc. NYP; “Magnetic Level Gauges” chapter in: Instrument Engineers’ Handbook - Measurement & Analysis, 4’th Edition, CRC Press, 2003; Author of the book “Linear Position Sensors, Theory & Application”, John Wiley & Sons, 2004; “Electronic Transmitters”, “Linear & Angular Positioning of Machinery”, and “Inerting Systems” sections in: “Instrumentation Engineers’ Handbook – Process Control, 4’th edition, (2005); “Hazardous area classification and management”, and “HART Networks” sections in the book: “Instrumentation Engineers’ Handbook – Digital Process Networks and Software, 4’th edition, publication in 2011 Magazines: Magnetostriction-Based Linear Position Sensors, SENSORS magazine, April, 1994: Tank Gauging Advances, Fuel Technology & Management, January, 1997: Magnetostrictive Position Sensors, Measurements and Control, September, 1998; A Moment in Positioning, PTDesign, February, 1999; Magnetostrictive Position Sensors (update), Measurements & Control, September, 1999; Position Sensors for Hydraulic Cylinders, Hydraulics & Pneumatics, November, 2000; Magnetostrictive Linear Position Sensors, Fluid Power Journal, April, 1999; Sizing & Applying Magnetostrictive Linear Position Sensors, Motion Systems, Feb., 2002; Position Sensors in Medical Applications, ECN, May 15, 2002; Featured in “Level Sensors Go Floatless”, Machine Design, May 8, 2003; "Guitar Man" feature article, The Pelican Post, Oak Island Press, Oak Is., NC, Winter 2005; The LVDT: A Simple and Accurate Position Sensor, SENSORS magazine, August, 2005; "Model Airplane Day!", FLYING MODELS magazine, September, 2006; “Kids Having Fun!”, Half-A Flyer magazine, January, 2012

Education/Credentials
BSEE, MBA, Management by Objectives - Honeywell, Total Quality Management - MTS Systems Corporation, Looking Glass Management Workshop - Center for Creative Leadership, Motion Control Systems - Western Michigan University, College of Engineering, Organizational Excellence - University of Cleveland, Finance for Executives - Sloan School of Business, MIT.

Awards and Honors
Vaaler award, EDN magazine, "Inerting for Safety", 1987 Listed in Who's Who in Engineering, in the South, in the World. "Total Quality Management" medal awarded by MTS Systems Corporation 1991 "Best Sequel" award for the video production: "For Engineers Only" at the MTS national sales meeting, Las Vegas, 1998 (written and directed by David S. Nyce) Voted "Most Effective Leader" at Center for Creative Leadership: Looking Glass, Greensboro, NC 1995 Silver Award for New Technology at SENSORS EXPO, in Chicago, 2001 for SEF Liquid Level sensor MTS Circle of Innovators award, 2003 Elected Master of Masonic Lodge #584 , Apex, NC, 2005 "Gold Honour Award" for outstanding service in York Rite Masonry, by the York Rite Sovereign College of North America, August 22. 2007 Board of Directors: WaaRev Sensors, and the Apex Historical Society Maynard Pearson House Plaque hanging in the Masonic Fellowship Hall, for Outstanding Service and Dedication to Apex Masonic Lodge #584, Apex, NC

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