4 to 20 MA Industrial Process Calibrator DIY | Electronics Instrumentation

Industrial and electronics instrumentation is a very expensive field and it's not easy to learn about it if we are just self-educated or a hobbyist. Because of that my Electronics instrumentation class and I designed this low budget 4 to 20 mA process calibrator that is perfect to test our processes controllers responses to an step or ramp input.

Here I show you step by step how to make yours.

If you are a visual learner I know that a video worth more than 1000 words, so here is a 2 parts Tutorial video. (I am a Spanish speaker, so please consider turning on English subtitles):

Step 1: Skills Needed

As you can noticed, nothing looks very difficult on this project, but you will need some basics knowings about:

-Welding.

-Wiring.

-Industrial Electronics.

Step 2: Components and Parts List

PCB I really recommend to use JLCPCB SMT Services to order yours.

SPDT Switches.

Banana Jacks

Wiring cables

10 Turns 100kohm potentiometer

Enclosure

Step 3: Circuit Diagram

Here is the Circuit diagram, it has all the internal conections of the circuit that will allow us to create the PCB design later.

I also attached the PDF of the Schematics so you can see it better.

DOWNLOAD Schematics

Schematic_Transmisor 4-20mA instrumentacion electronica_2020-12-08_11-17-12.pdf
Download

Step 4: PCB Design and Ordering

For the implementation of a good project we need a reliable assembly for the circuit that makes it up, and there is no better way to do it than with a good PCB.

Here you can download the Gerber, BOM and Pick & Place Files for free, the ones you need to order your PCB on your PCB manufacturing company.

I suggest JLCPCB:

📦$2 for Five - 4 Layers PCBs & cheap SMT (2 Coupons)

DOWNLOAD ALREADY DESIGNED BOARD, Gerber + Pick & Place + BOM

Step 5: Enclosure and Housing

Here you can buy the enclosure and see it dimensions to build or 3D print yours

Step 6: Project Assembly

You can place all the switches and outputs where you prefer, in my case I made some holes with a drill and placed the switches and the potentiometer with it nuts.

In the side, I made some holes for the banana jacks for the Loop input and for the current test probe.

Step 7: Connecting the Loop

From your 24 volts power supply (+ positive) connect to the (+) input of the Loop of the calibrator.
Continue from the (-) to the positive of the grapher.
Close the loop connecting the negative of the power supply with the negative of the grapher.
Connect you ampmeter in the banana jacks in current mode.

Step 8: Final Test

Turn on the power supply, and look at the current showed by your ampmeter.

Test the different steps, and verify they produce the right current. If not, set the trimpots in the circuit until you get the right value.

Finally, you can see the pictures of the system through the grapher and the lectures in real time. As you can noticed, the steps are succesfully produced, and we also can vary the current with the potentiometer.