This post serves as a landing pad for frequently asked questions that arise when designing with 4-20mA current loop transmitters. Keep in mind that there are other common output current ranges such as 0-20mA or 0-24mA, and the ideas presented in the following links can apply to those ranges as well. The information in this post focuses on the theory behind 4-20mA current transmitters, and common questions surrounding TI's XTR current transmitters.
Watch the TI Precision Labs Series on Current Loop Transmitters here:
Video1: Introduction to 4-20mA current loop transmitters
Video2: Current loop transmitters configurations
Video3: Analog Input 2-wire 4-20mA Transmitters
Video4: Analog Input 3-wire 4-20mA Transmitters
What is a 4-20mA current transmitter?
What is a 2-wire 4-20mA current transmitter?
What is a 3-wire 4-20mA current transmitter?
What is a 4-wire 4-20mA current transmitter?
How do I choose a 4-20mA transmitter?
Does TI have integrated 4-20mA transmitters for inputs from RTDs (resistive temperature detectors)?
Does TI have integrated 4-20mA transmitters for inputs from bridge sensors?
Can I use multiple XTR devices if I have multiple DAC outputs or multiple sensors that share a supply and ground?
Are there reference designs that can help me build a 4-20mA transmitter?
What types of applications or end equipment are 4-20mA transmitters used in?
The minimum output current of my 2-wire 4-20mA transmitter is greater than 4mA.
Can I use a 2-wire transmitter with a sensor or microcontroller that uses its own supply?
Why does my 2-wire 4-20mA transmitter output not reach the full 20mA?
When do I need to input isolate a 3-wire transmitter?
Can I use the XTR300 or XTR305 with a single supply?