Hi All, I need to generate a 4-20mA output from a resistive probe, I have connected the probe to 5V through a 100K resistor and reading it into the A/D of a uP, works great!, then I need to add the 4-20mA output, I have connected the probe to a 741 opamp and I am getting weird readings, it is also changing the value I have on my uP when I connect the 741, does anyone have some ideas on a simple 4-20mA output?