Im working on a project to read a 4-20ma pressure transducer that normally gets power from a 9-36v supply and I know how to wire the measuring circuit for that setup. my issue is I am now going to use a 3.6v to 12v converter and mosfet to power up the loop take a reading and shut the loop down after. My problem is how do I wire this circuit since both the sensor and arduino will be powered from the same battery.
Currently my circuit looks like the image attached.
Nothing will be applied to senor, A0 is attached to arduino as in input.
I have since changed the diagram ( see attached ) to avoid measurements being effected by the mosfet.
Better to replace the 100ohm resistor with a 51ohm resistor (E24), and enable 1.1volt Aref in void setup().
Then readout is more stable, and you use the full resolution of the A/D.
Increase R16 to 10k and add a 100n cap from A0 to ground for increased pin protection and stability.
Leo..
AFAIK most Arduinos have a 1.1volt Aref, but you can check in the products pages of this site.
If there isn't any 1.1volt Aref, increase the 51ohm resistor to 160ohm (E24 value).
That should use max A/D range at ~3.3volt default Aref. Stability will then depend on VCC.
Leo..
