I have a servo system using a JRK12V12 and when I use a 10 K feedback pot everything works just fine. Pot connected to AUX, FB & GND. Input range set to 0 and 4095. Powered only by USB with no motor connected. If I change the pot value to 30K I get a pot disconnect error at about 3000 counts of feedback. The plot shows the pot position accurately but I get the error flag. Disable the error flag and everything works fine. A DVM connected between FB and GND tracks the pot position monotonically. Obviously the source impedance of the 30K pot is 3X the 10 K pot source impedance. It acts like the FB input on the JRK outputs a glitch into the higher source impedance and trips the error flag.
It seems like the FB pin should only go to the PIC A to D input and shouldn’t put out anything. Several different JRK units behave this way.
What’s happening here and what is the official maximum pot resistance?
The 3T 30K I am using are mechanically unique and expensive to duplicate in a lower value.