Hi Ray , I have tried it with the sheild grounded at both ends and just one end , at the VFD and in the main cabinet, each in turn , no change.
I am using the C11 board from CNC4PC , same BOB I am using on 3 other machines running VFD .
I have to 10v power supply from the VFD attached to the external power supply input for the analog out on the BOB , The analog out signal 0-10v is attached to the analog input on the VFD .
There are two dc relays on the c11 BOB , both with NO contacts and a common in , one is triggered by pin 1 the other by pin 16 . The VFD has a 24v power supply for the inputs that choose direction , in the VFD I have the switch set to source inputs and the + from the 24v power supply run to the common in term on the relays and one wire each to the two terminals in the VFD for forward and reverse . I have set the switch to sink and attached the - to the relays, same interference.
M3 is set to output 1, output one is set to trigger pin one , When M3 is called out the relay at pin one is energized and completes the circuit to the VFD to turn clockwise (forward with my rear turret lathe). Which it does until the watchdog trig thing puts the machine in estop. Reverse is wired similarly to the relay on pin 16 , m4= output2. output2=pin 16 , m4 callout energises the relay at 16 and the spindle turns anti-clockwise until the watch dog triggers estop .
I am pretty sure the BOB to VFD wiring is correct , I have been using the same setup (smaller vfd) on three other machines for quite a while with no problems. I am sure I am just overlooking something simple