[FAQ] How do I choose a 4-20mA transmitter?

Choosing a 2, 3, or 4-wire transmitter depends on how accessible a power supply is to the transmitter, and what type of signal your source is. You can choose to build a discrete 4-20mA transmitter, or use a partially or fully integrated 2-wire or 3-wire transmitter from TI. Make sure to read the FAQs for:

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?

2-wire transmitters are loop powered devices most commonly used to monitor a remote process with no access to a local supply. The sensor is powered by the transmitter. The transmitter and sensor must consume less than 4mA. If your system requires more than this, you may need to use a 3 or 4-wire transmitter. The sensor ground cannot be connected to the loop supply ground.

TI has the following 2-wire 4-20mA transmitters:

• Analog input, analog output: XTR101, XTR105, XTR106, XTR112, XTR115, XTR116, XTR117
• Digital input, analog output: DAC161S997, DAC161P997

3-wire transmitters can be used with a local supply to transmit control data to remote devices. The ground of a 3-wire transmitter is shared with the receiver. Because 3-wire transmitters have a local supply, the sensor and its conditioning circuitry can consume more than 4mA. This allows 3-wire transmitters to use other common output current ranges such as 0-20mA or 0-24mA.

TI has the following 3-wire 4-20mA transmitters:

• Analog input, analog output: XTR110, XTR111, XTR300, XTR305
• Digital input, analog output: DAC8771, DAC8775, DAC8760, DAC8750, DAC7760, DAC7750

4-wire transmitters have separate paths for the power current and signal current, and the receiver does not share a common ground with the transmitter supply. Similar to 3-wire transmitters, 4-wire transmitters can also use other output current ranges such as 0-20mA or 0-24mA.

TI also offers 4-20mA transmitters that provide sensor excitation and signal conditioning

See: Does TI have integrated 4-20mA transmitters for inputs from RTDs (resistive temperature detectors)? and Does TI have integrated 4-20mA transmitters for inputs from bridge sensors?