Proportional Band and Reset Rate Converter
Different controllers use different tuning units. Convert gain to proportional band and integral time (minutes per repeat or seconds) to reset rate (repeats per minute).
- PB (%) = 100 ÷ gain
- Repeats per minute = 1 ÷ (minutes per repeat)
Tuning Unit Conversions
Reset rate (repeats/min) = 1 ÷ Ti (min/repeat)
Ti (s) = Ti (min) × 60
Worked example
A gain of 2.5 is a proportional band of 40 %. An integral time of 3 min/repeat equals 0.333 repeats/min or 180 s/repeat.
Frequently Asked Questions
What is proportional band?
The percentage of input span needed to move the controller output through 100 %. PB = 100 / gain, so PB 50 % equals gain 2.
What is the difference between minutes per repeat and repeats per minute?
They are reciprocals. Integral time is minutes per repeat; reset rate is repeats per minute.
Which controllers use proportional band?
Many older pneumatic and single loop controllers, and some DCS systems such as those inherited from Foxboro, use PB; most modern systems use gain.
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