4-20mA current loop

[mychangl]

hi there !!
anyone can give me some info how to interface 4-20mA signal from pressure transducer to a PIC ? Any suitable device to use ?

Thx !

[mister_e]

op-amp in between? Change the current reading into voltage...

Or use something like
http://focus.ti.com/lit/ds/symlink/rcv420.pdf
if still available ...

[mat janssen]

Or just take a resistor of 250 ohms.(4 resistors of 1K in parrallel)
Connect 1 point of the resistor to an analog input of the processor and the + output of the current device. The other point of the resistor to the gnd of the processor and the - output of the current device.
The you will have 0 to 5 volt for 0 to 20 mA.
The 4 mA (1volt in this case) you subtract in the programm and the rest is your value.

[Luciano]

Hi,

(Read first Mat Janssen post).

See this link:
http://www.processautomationcontrol.com/download/4-20mA-Current-Loop-Primer.pdf

Best regards,

Luciano

[dragons_fire]

when i made an Airspeed and altitude recorder for my RC planes, i used an opamp between the pic and pressure sensors.. it worked well, if i can find the documentation for it, i will post it...

if you search for model rocket altimeter schematics, you will find lots of people that have used pressure sensors with PICs.

[mychangl]

Got the concept. Thx guys !!!! :-p