current limiting
current limiting
(OP)
Hi,I am building a 4-20mA circuit. I built it by getting 4-20V and throwing a 1K resistor in. What is the cons to this circuit as opposed to building a 4-20mA with an XTR116 Burrbrown?
Also, my min(4ma) is good but the 20mA drifts, how do I limit the current to 20mA using transistors?
Thank you.
Also, my min(4ma) is good but the 20mA drifts, how do I limit the current to 20mA using transistors?
Thank you.





RE: current limiting
You could build your own transmitter, but why bother if you have the XTR116. Incidentally, Burr-Brown were taken over by Texas Instrument, and they still make this device.
RE: current limiting
RE: current limiting
To answer your question, the Burr-brown part is way more accurate. The resistor will change value as it heats up (the type of resistor will determine how bad). Now you have issues with the voltage source accuracy and the resistor accuracy affecting your circuit. In addition, you have no feedback so the circuit can correct itself.
Try going to onsemi.com and look at app notes. You will find an easier, more accurate circuit using a single op-amp. Throw your circuit in the trash unless you want to learn more about electronics. Good luck.