rta53
Lifetime Supporting Member
One more question from a rookie ControlLogix programmer. As I mentioned in another topic I am troubleshooting an existing program for a customer. I have a subroutine that has 2 PID instructions for controlling 2 VFDs that are controlling 2 pumps. One of the PIDs gives me an output when it is called for in the program. I cannot get any output from the other PID. The PID that is working has a timer done bit in the rung that toggles on and off every 2 seconds. The timer for this done bit is in the rung that immediately precedes the PID rung. Several rungs down is the second PID which also has the same timer done bit. Someone told me that I needed to user another timer and done bit and put the timer in the rung before the PID instruction. They said the scan time was too fast for the same done bit to be used since the timer was several rungs before the PID. Does this sound right? Seems too easy.