PDA

View Full Version : 4 to 20 ma signal DAQ question



Snap
- 3rd October 2007, 03:40
This might be a total noob question but I would like to know how you measure current with the pic. I can see several adc ic's and options that measure voltage but not current. I am starting a data logging project and the source signal is 4 to 20 ma.(Miltronics Water level meter) The difference in voltage at that small current change seems too small to measure? Can I use the ADC on the pic or do I need a special IC current to voltage converter. I have also seen some solutions with an op amp but would prefer an all in one IC.
Thanks
Snap

mackrackit
- 3rd October 2007, 04:15
A resistor is all you should need to convert the signal to a 1 to 5 volt range. A couple of links to look at.

http://www.teicontrols.com/4-20.html

http://www.allaboutcircuits.com/vol_1/chpt_9/3.html

Snap
- 3rd October 2007, 18:48
I am new to this electronics stuff (microbiology-chem background), but I am a fast learner and can not get over the fast and accurate responce I recieve in the forum. I try to help out in threads that deal directly with problems I have had and hope to one day help people in the same way I have been helped. I knew a voltage divider would some how be involved but I was unsure of the ohm's. I researched every way I knew how and still could not find the links you provided. By the way I can't get the spell checker to work in this forum and am lost whith out it.
Snap

mackrackit
- 3rd October 2007, 18:53
Spelll checker? What it that:)

Use Fire Fox.