Process Control and Instrumentation MCQs 2026

Integral mode eliminates

1. A steady-state offset for step disturbance in stable loop ✓
2. B all oscillations instantly always ✓
3. C need for sensor ✓
4. D process time delay completely ✓

Transfer function G(s) relates

1. A only time-domain impulse visually ✓
2. B only pipe schedule ✓
3. C only catalyst surface area ✓
4. D Laplace transform of output to input ✓

Second-order overdamped response has

1. A sustained oscillation always ✓
2. B inverse response only always ✓
3. C undefined output ✓
4. D no oscillation ✓

Cascade control uses

1. A only single sensor far downstream ✓
2. B only open-loop scheduling ✓
3. C secondary loop to correct disturbance before primary loop ✓
4. D only laboratory off-line tuning ✓

Feedforward control acts on

1. A only past error integral ✓
2. B only operator guess ✓
3. C measurable disturbance before it affects controlled variable ✓
4. D only annual maintenance ✓

Ultimate gain in Ziegler-Nichols closed-loop method found at

1. A critical gain causing sustained oscillation ✓
2. B zero gain always ✓
3. C maximum sensor span ✓
4. D minimum reflux ✓

Bode plot shows

1. A only time step response only ✓
2. B only XY composition ✓
3. C only tray temperature profile only ✓
4. D gain and phase versus frequency ✓

Feedback control compares

1. A only feedforward without measurement ✓
2. B measured variable to setpoint and corrects via controller output ✓
3. C only manual valve position always ✓
4. D only laboratory assay weekly ✓

PID controller combines

1. A only on-off relay without hysteresis ✓
2. B proportional, integral and derivative actions ✓
3. C only ratio without measurement ✓
4. D only cascade without secondary ✓

Derivative mode responds to

1. A only steady error magnitude ✓
2. B only setpoint constant always ✓
3. C rate of change of error ✓
4. D only manual mode ✓