
Building a 4–20mA current transmitter and receiver for some upcoming automation projects.
After building the 4–20mA current transmitter, it was time to build a receiver. I used the companion Burr-Brown (TI) RCV420 precision current-loop receiver IC. The RCV420 is a monolithic circuit that converts a 4–20mA input signal into a 0–5V output signal, and has a 0.1% overall conversion accuracy.

The RCV420 utilizes a plus and minus 15 volt DC supply, and is not loop powered. I used a Recom RB-1215D, DC to DC converter that uses a 12 VDC input, and outputs +/- 15 VDC at up to 33 mA. I also used a Polymeric 150 mA PTC Resettable Fuse for the 12 volt input to the DC to DC converter along with some capacitors for EMC Filtering.

For filtering the +/- 15V power busses I used some United Chemi-Con 120 uF at 20 volt capacitors. These are Aluminum — Polymer capacitors with an ESR of 20 mOhms and a lifetime rating of 15000 Hrs @ 105°C. Each buss also has a 0.1 uF and 10 nF ceramic capacitor located close to the IC power pins.
To protect the input sense resistor, I chose to use a 0.032A, Lifflefuse Series 217 fast-acting fuse, as this introduced the least amount of loop voltage drop of the three recommended solutions from the datasheet.
The only other item of note is capacitor C9, a 1 uF ceramic on the IC’s voltage reference Noise Reduction pin #7 to reduce high frequency noise of the internal 10 volt reference.

I did attach an Assmann WSW Components V5619A 16 pin DIP heatsink to the RCV420 IC to reduce the affects of self-heating affecting the precision of the circuit.
I did try something new with 4–20mA transmitter and receiver boards in that I used a hatched polygon pour for the non-ground sides of the board. I used a width of 10 mils and a spacing of 40 mils for the hatch pattern with a 18 to 20 mil isolation from other traces.
For the most part, it is a simple circuit that works very well for my intended use. I will mount this board in a enclosure with several other boards and power supplies including the loop 24 volt DC supply
EagleCAD V7.7 board & schematic ZIP file for 4–20mAReceiver
OSH Park printed circuit boards for the 4–20mA Current Receiver
The Transmitter Schematics are linked here, not the Receiver Schematics. Are they still available?
Hi Shannon,
Thanks for catching that. I have corrected the link.
Greg(Barbouri)