cli21 wrote:
1. According to the PID user manual, the PID VI uses trapezoidal integration for the the integral action. The formula is shown in attachment. I wonder does the dt in PID VI the same with Δt in the formula?
Yes, that's correct.
cli21 wrote:
2. If dt is leaved unwired, according to labview help, "this VI calculates the time since it was last called using an internal timer with 1 ms resolution." My question is if I use the PID Vi inside a while loop, does this mean the dt will be equal to the while loop rate?
Yes, dt will be the time between loop iterations. Each time the PID VI executes it will recalculate dt as the time since the previous execution.
