I have a device that has 4-20mA output, referenced to circuit ground, which I used XTR111 to realize the transmitter. This device works without problem in most situations. But I got reports that in some situations, it has some issues. When the receiver(a plc) is connected to the transmitter over 30-40m shielded cable (grounded on the receiver side) in an industrial environment the output increases suddenly about 1-1.5mA at the receiver side and oscillates a bit.. I did not inspect the site yet but they say plc has a 220V supply which is a EH150 Hitachi plc. Also they say when the connection to the plc is severed the situation goes away. They also say, there is no voltage or anything at plc analog input. I've tried with 100m cable with different type of receivers with seperated ground with the transmitter in the office and did not face any problem. What may be the issue? Does using current loop transmitter like xtr117 may improve the situation? May isolating the mA improves the issue? Thanks.