GATE 2023 BT – Question 64

Fundamentals of Biological Engineering · Process Control: Measurement devices, valves, first and second order systems, feedback and feed forward control, P, I and D controllers and tuning · 2 marks · Numerical answer

A proportional controller is used to control the temperature of an autoclave from 60 C ° to 130 C ° . If the proportional band setting of the controller is 25%, the proportional gain value is __________.

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Correct answer: 4

Explanation

For a proportional controller, the **proportional band (PB)** is the percentage of the input range over which the output moves through its full range. The gain is the reciprocal of the band:
$$K_c=\frac{100}{PB}=\frac{100}{25}=\mathbf{4}.$$

A 25% band means the controller output goes through its full range when the temperature changes by a quarter of the span, so a change of 1% of span gives a 4% change in output.