Glossary · TOF
What is Off-delay timer (TOF)?
A block whose output Q stays true for PT after IN goes false, then drops.
Used to keep a cooling fan running after the motor stops, to hold an alarm lamp on long enough to be seen, or to ride through a brief signal dropout.
The difference from TON: one delays the rise, the other delays the fall. With them comes TP, which gives a fixed-length pulse however long the input stays on.
Related terms
- On-delay timer (TON)
- A standard function block whose output Q becomes true after IN has stayed true for PT without interruption, and resets as soon as IN drops.
- Function block (FB)
- A unit with inputs, outputs and internal memory that persists between scans, used by declaring an instance of it.