Would anybody give me a pointer to an ic/simple cicuit that converts the output of a d/a to a 4-20mA loop. I prefer 5 or 12 V supply voltage. Sorry if this is a trivial question, but I am a software girl. Svenja
Best idea for this application. We use these devices in many our digital & analog I/O applications, as they provide for good isolation as well.
Svenja, Burr-Brown has a number of chips beginning with XTR-1xx that fill this need. I've used some older ones, but I did a quick search and found that they've got newer, cheaper parts. This is from 1-Jun-200 Electronic Component News: New Products 4-20 mA Current-Loop Transmitters for Industrial Sensors and Signal Acquisition Burr-Brown's new XTR115 and XTR116 are low-cost, precision 4-20 mA current-loop transmitters targeting basic 4-20 mA current loop applications including smart transmitters where sensor signals are processed with microcontrollers when electrical power is not available at the sensor site. They are also well suited for a variety of other high volume applications, such as remote signaling from a switch contact or simple variable resistor in, for example, an air duct or liquid level sensor. A 4-20 mA current-loop transmitter provides accurate transmission of analog signals from sensors (used to monitor physical parameters in industrial processes such as temperature and pressure) to remotely located measurement equipment. The devices feature low quiescent current (200 =B5A), wide loop supply range (7.5 V to 36 V), 5 V regulator for powering external circuitry, precision voltage reference for sensor excitation, and low span error (0.05%). The XTR115 and XTR116 are priced from $0.95 in 1,000-piece quantities and packaged in an SO-8. Burr-Brown Corp., P.O. Box 11400, Tucson, AZ 85734; (800) 548-6132; Take a look at their site: www.burr-brown.com . Happy hacking, Willy Smith Numatics Costa Rica
Acromag makes several different signal conditioners that should work for you. www.acromag.com Grayg Ralphsnyder
Svenja, Try www.iomega.com . They have some good, inexpensive convertors. Bob Robert J. Dusza, Jr. Treatment Manager (V) 1-860-647-3219 (F) 1-860-647-3150 E-mail - Rdusza@ci.manchester.ct.us Manchester Water & Sewer Dept. 125 Spring St. P.O. Box 191 Manchester, CT 06045-0191
I just found this website, so your problem is likely solved by now, but when it comes to 4-20mA signals I have the following recommendations: If the "user" of the signal is known, match the circuit characteristics to their need. If you are designing equipment with a 4-20mA output that can be used generically by other instruments, let the 4-20mA loop be powered in a way that lets it be jumpered for either external or internal power. Use an optically isolated converter and a power supply not referenced to your device for powering the loop. If production equipment, understand the resolution limits of your 0-5 vdcsignal and only buy as much resolution as needed.
I was looking at this myself the other day. There is a simple circuit with an op-amp that converts voltage to current. It takes an op-amp and Look for voltage to current op-amp circuits in any op-amp circuit collection
This is Venkatesh, the hardware boy. To your question, if your application is specific, I can give you a solution. Even though I provide you a rough solution. You can try XTR 116 ic which provides 4-20 mA current output.
This is not a trivial question, I also am looking for a good solution. The XTR 115 / 116 are good for sensors which are not connected to a power source, but are not good for what you want to do. I am starting to look into adjustable current voltage regulators as a cheap solution. It is surprizing that no one out there makes a chip
that generates 4-20ma from a 0-5 V input without requireing sometype of optical isolation. Have you come up with a solution yet. BTW I design products that go into the auto manufacturers for various control systems.
Try this It is simple but effective.
Good Luck D