PLC Timer Preset Calculator
Work out the preset value for a TON, TOF or RTO timer from the delay you need and the timer time base, and the longest delay the timer can hold.
- Preset = delay ÷ time base = 2.5 ÷ 0.01 = 250
Timer Preset Formula
Maximum time = maximum register value × time base
Rockwell Logix TON timers use a 1 ms base with a 32 bit preset; older SLC and S5 style timers use selectable bases. IEC 61131-3 TON timers take a TIME value directly (for example T#2s500ms).
Worked example
A 2.5 s delay on a 10 ms time base needs a preset of 250. A 16 bit signed preset limits this base to 327.67 s.
Frequently Asked Questions
How do I calculate a PLC timer preset?
Divide the required time by the time base: 5 s on a 100 ms base is a preset of 50.
What is the maximum time of a 16 bit timer?
32767 × time base: 327.67 s on a 10 ms base.
What is the difference between TON and TOF?
TON delays switching on; TOF delays switching off.
Learn more on the blog
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