# Ability of PLC's to communicate via 4-20mA and 0-10volts between laboratory devices and the PLC

#### bluecaribou521!

Joined Apr 17, 2020
2
Hey guys, I'm studying electrical engineering technology and the Coronavirus turned my capstone project into a research paper. My assignment is on PLC's, which we have covered the basics of, but I still know little about how they operate. Here is the prompt:

"Research the ability of PLC's to communicate via 4-20mA and 0-10volts between the laboratory devices and the PLC.

This would include how to communicate between these devices using an analog device that has 0-10 volts and converts to 4-20mA.

Look up information about the circuits required for converting this function 0-10v to 4-20mA and 4-20mA to 0-10volts. Look up circuits that can do this on GOOGLE. Shouldn't be too difficult, but I would like this information in a particular format using a schematic, along with information how this can be done ."

If anyone has any information that might help me out with this paper that would be amazing. Or if you know of any resources or websites that might cover this topic, that would help too. I am really lost and don't know where to start. Thanks!!

#### WBahn

Joined Mar 31, 2012
29,146
MOD NOTE: Moved to Homework Help (is an academic assignment)

#### WBahn

Joined Mar 31, 2012
29,146
Here's another amazing thing you might try: Look up circuits that can do this on GOOGLE.

Do that and learn what you can (that's sometimes called "research") and then ask specific questions related to what you have learned.

#### GetDeviceInfo

Joined Jun 7, 2009
2,173
Are you thinking to add communications embedded into the signal ? Check out Hart for the current loop.

Joined Jul 18, 2013
27,601
Most PLC's now have the ability to communicate over a few methods. Modbus RTU. EtherNet/IP. Ethernet TCP/IP.
Max.

Joined Jan 15, 2015
7,217
"Research the ability of PLC's to communicate via 4-20mA and 0-10volts between the laboratory devices and the PLC.

This would include how to communicate between these devices using an analog device that has 0-10 volts and converts to 4-20mA.
Just to make sure everyone is on the same channel I see this as laboratory devices such as sensors of various engineering units sending data to a PLC using 4 ~ 20 mA or 0 ~ 10 volts. Would that be about correct? Most sensors I have worked with send 4 to 20 mA which is passed through a resistor on the PLC resulting in a voltage. Normally 2 to 10 volts or 1 to 5 volts. Would that be what you have in mind? Additionally the PLC can output voltages or currents to devices like a I to P converter for a pneumatic valve.

Then we have communications as Max mentions.

Ron

#### WBahn

Joined Mar 31, 2012
29,146
Look up information about the circuits required for converting this function 0-10v to 4-20mA and 4-20mA to 0-10volts.
As best I can tell, the purpose of the assignment is primarily to explore conversion back and forth between 0 - 10 V and 4 - 20 mA.

So the scenario I think that is being implied is that there is a sensor that outputs 0 - 10 V and a PLC that takes in input that is 0 - 10 V, but the communication between them is to be a 4 - 20 mA loop.