| ??? 11/14/06 19:18 Read: times |
#127987 - Are the devices plugged >> Erik Responding to: ???'s previous message |
Hi Erik,
Many thanks for your suggestions. Are the devices plugged in in an outlet with ground? Have you grounded the PC? The devices have only 2 supply terminals (Line, Neutral). So there is no possibility of connecting the Earth Terminal. And These instruments are PID Temperature Controllers (made in Taiwan), and usually all of them use SMPS Supply inside these instruments but they do NOT have an Earth Terminal. (nor the GND Terminal for RS485). Yes, The PC is properly Grounded, and so the RS232-RS485 Convertor. is that BOTH ends? Yes the terminating resistor are at both ends of the cable only. What I would consider is to split the RS 485 in two one for the instruments and one for the AC drives. To test this - what happends if you disconnect the instrunents and run the AC drives only? Yes, I had tested this. With Only the AC Drives (all 4 of them), the communication works OK till all the Drives are in the "STOP" Mode. Anyone of them goes in "RUN" Mode, the communication starts failing. One last thought: do you have 3 resistor termination at either end, if not try it (it is in 10 ways) I am Not sure about this because the convertor is purchased and in a ready-to-use box. But I will definitely open it up and check for this suggestion. Thanks Again, From Kiran V Sutar |
