Trane Tracer ZN517, Installation And Operation Manual, Page: 79 / 111

Sampling frequency
CNT-SVX12C-EN 67
The control system should always wait to process the result of a change
before making another change.
Figure 23 shows the process variable if sampling times are too fast,
acceptable, and barely acceptable. If the sampling frequency is too fast (2
seconds), the process variable begins to oscillate and finally destabilizes
because the PID loop output drives the actuator to extremes.
Figure 23. System stability with different sampling times
Sampling freq. = 10 s Sampling freq. = 20 s
Sampling freq. = 2 s
(system destabilizes if
sampling freq. is too fast)
Time
P
rocess v
a
riable