Hi all,
I have this Knick Stratos e transmitter wich is capable of converting pH-measurements to a 4-20mA current signal. To measure this output signal I use a 250 ohm resistor to map the voltage on a scale from 1-5V. However, when I'm trying to measure this voltage using my arduino, I don't get a signal at all. Could it be that my wiring is incorrect (see diagram), should I somehow connect building ground to my arduino. Any suggestions?
didn't you swap the lines?
Have you checked the voltage with a DMM?
Hi, can you tell us the make and model of the transmitter.
Have you got it powered?
If not you may need to supply loop power of 24Vdc to get it to work, BUT before trying anything, GET the manual and check how it should be connected.
Have you tried measuring the voltage across the resistor with a DMM and the arduino disconnected?
Tom...... 
Found the problem, had to swap the lines. Thx for the comments!
nnicola:
Hi all,I have this Knick Stratos e transmitter wich is capable of converting pH-measurements to a 4-20mA current signal. To measure this output signal I use a 250 ohm resistor to map the voltage on a scale from 1-5V. However, when I'm trying to measure this voltage using my arduino, I don't get a signal at all. Could it be that my wiring is incorrect (see diagram), should I somehow connect building ground to my arduino. Any suggestions?
It may be OK for home or short distance use , but 4-20 ma current signal loop by definition should be isolated from whatever is processing it
You could replace the direct connection using optocoupler to accomplish that if necessary.
Have fun.