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Dear Friends; Today i am stuck and do not understand how i fix the following issue? 1. We have PH controller from Hannah Model HI 8711T , PH transmitter HI 8614L and PH probe. On the terminal blocks of the controller there are  4-20mA (Isolated).  2. We have FX 2N-4AD analogue module to read the PH value on the HMI. 3. First i connect the 4-20 mA as follows Short the V+and I+ terminals and connected it to the -ve of the controller 4-20mA terminal. I- connect withe the -ve of 24 VDC. and +24 applied to the +ve of controller 4-20mA terminal. But the reading not read by the controller. Then i change the wiring as follows Short the V+and I+ terminals and connected it to the +ve of the controller 4-20mA terminal. I- terminal connected to the -ve of the controller 4-20 mA terminal. By this the reading is shown perfectly. But the issue is after 10 to 15 second all the values that is on the LCD of controller , transmitter and on HMI fluctuate. Even i connect and disconnet the shield on the Module side but the issue is not fixed. How i fix it, and guide me how i wire up properly FX2N-4AD with 4-20 mA isolated output of the controller?   Thanking you, I will remain