Q1. Which feature most clearly distinguishes a microcontroller from a general-purpose microprocessor?

A. It can execute only arithmetic instructions B. It integrates CPU, memory and peripherals on one chip C. It never contains timers D. It always requires an external CPU

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A microcontroller is intended for embedded control and commonly integrates a processor core, memory, timers, communication interfaces and GPIO on a single chip.

Q2. The primary function of a microprocessor in a control system is to:

A. Generate hydraulic pressure directly B. Execute stored instructions and process data C. Act as a mechanical actuator D. Measure temperature without a sensor

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A microprocessor executes instructions, performs arithmetic and logic operations, processes data and generates decisions. Sensors and actuators require suitable interface circuits.

Q3. Which memory is commonly used to store firmware in a modern microcontroller?

A. SRAM B. Cache RAM C. Flash memory D. Register file

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Flash memory is non-volatile and retains its contents without power, making it suitable for firmware storage. SRAM is volatile and is normally used for temporary data.

Q4. An ADC in a controller is primarily used to:

A. Convert digital data into hydraulic pressure B. Convert an analog sensor signal into a digital value C. Increase CPU clock speed D. Store the program permanently

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: An analog-to-digital converter samples an analog signal and represents it as a digital number for processing by the controller.

Q5. Which peripheral is commonly used to generate periodic interrupts in a microcontroller?

A. ADC B. Timer/counter C. EEPROM D. GPIO resistor

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A timer/counter counts clock events and can generate an interrupt at a programmed interval, making it useful for periodic control tasks.

Q6. Which interface is normally used for asynchronous serial communication?

A. SPI B. PWM C. UART D. ADC

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: UART provides asynchronous serial communication using transmit and receive lines and a specified baud rate. SPI is synchronous.

Q7. A GPIO pin configured as an output is primarily used to:

A. Store program memory B. Provide or control a digital signal to an external circuit C. Perform floating-point division only D. Replace the system clock

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: GPIO means General-Purpose Input/Output. In output mode it can provide a logic HIGH or LOW signal to an external interface.

Q8. A typical PLC scan follows which sequence?

A. Output update → program scan → input update B. Program scan → shutdown → input update C. Input update → program scan → output update D. Program scan only

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: A typical PLC reads inputs, executes the user program using the input image, and then updates physical outputs.

Q9. The PLC component that interfaces field sensors and actuators with the CPU is the:

A. Heat sink B. I/O module C. Programming cable D. CPU fan

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: PLC I/O modules provide the electrical interface between field devices and the CPU. Input modules receive sensor signals and output modules command actuators.

Q10. A PLC is widely used in industrial automation because it:

A. Can only perform mathematical calculations B. Is designed for reliable industrial logic and sequential control C. Needs no I/O interface D. Cannot operate sensors

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: PLCs are rugged industrial controllers designed for reliable operation, diagnostics and deterministic control of industrial I/O.

Q11. Which is an IEC 61131-3 PLC programming language?

A. HTML B. Ladder Diagram C. SQL D. Fortran only

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Ladder Diagram is a standardized PLC programming language. Function Block Diagram and Structured Text are other commonly implemented IEC 61131-3 languages.

Q12. A normally open PLC contact instruction is logically TRUE when its associated bit is:

A. 0 B. Floating C. 1 D. Analog

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: A normally open logical contact becomes true when its Boolean variable is TRUE, conventionally represented by logic 1.

Q13. A watchdog timer is primarily used to:

A. Increase hydraulic pressure B. Detect abnormal execution or excessive scan time C. Measure torque directly D. Store calibration data permanently

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A watchdog supervises execution timing. If the controller does not complete its expected operation within a limit, a fault response or reset can occur.

Q14. Which characteristic is especially important when controlling a fast-changing process?

A. Very slow sampling B. Adequate sampling frequency and deterministic execution C. Large mechanical inertia D. No input filtering

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Fast processes require sufficiently frequent sampling and predictable execution. Poor timing can cause delayed response or missed events.

Q15. The resolution of an ideal n-bit ADC is mainly related to:

A. Sensor color B. The number of digital codes over its input range C. CPU instruction length only D. Actuator stroke

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: An n-bit ADC provides 2^n possible codes. More bits provide finer quantization for a fixed input range.

Q16. PWM is commonly used in controllers to:

A. Store source code B. Control average power delivered to loads such as motors C. Measure resistance without an ADC D. Replace communication protocols

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Pulse-width modulation changes the duty cycle of a switched signal, controlling average voltage or power delivered to suitable loads.

Q17. A real-time controller must ensure that:

A. All calculations are manual B. Control calculations occur within required timing deadlines C. Sensors are never sampled D. Outputs remain permanently OFF

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Real-time control requires results to be generated within specified timing constraints as well as being mathematically correct.

Q18. Which device is generally suited to high-speed general-purpose computation with external peripherals?

A. Relay B. Microprocessor C. Limit switch D. Thermocouple

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Microprocessors are general-purpose processing units commonly paired with external memory and peripheral devices.

Q19. Which device integrates processor, memory, timers, GPIO and communication peripherals in one package?

A. Transformer B. Microcontroller C. Induction motor D. Solenoid valve

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Integration of CPU, memory and peripherals is a major advantage of microcontrollers for compact embedded control.

Q20. An output coil in PLC ladder logic generally represents:

A. A physical resistor B. A command to set an output or internal Boolean according to preceding logic C. A hydraulic cylinder D. A temperature sensor

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: An output coil represents the result of the preceding ladder logic network and can control a physical output or internal Boolean variable.

Q21. Which PLC timer turns its done state ON after an enabling condition remains TRUE for a preset time?

A. CTU B. TON C. MOV D. ADD

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: TON means Timer ON-Delay. It accumulates time while enabled and becomes done after the preset delay.

Q22. A PLC counter is most appropriate for:

A. Measuring analog voltage without an input module B. Converting AC to DC C. Counting discrete events such as products passing a sensor D. Generating hydraulic pressure

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Counters are designed to count discrete transitions or events such as products detected by a photoelectric sensor.

Q23. Which serial interface is synchronous and normally uses a clock line?

A. UART B. SPI C. Analog input D. Relay contact

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: SPI is synchronous and normally uses a clock plus data lines, with chip-select signals for peripherals.

Q24. Interrupts are useful because they:

A. Increase actuator stroke B. Eliminate sensors C. Allow urgent events to receive processor attention without continuous polling D. Convert binary data into pressure

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Interrupts allow the processor to service time-critical events such as timer ticks, encoder pulses and communication reception.

Q25. A proportional controller produces an output proportional to:

A. Integral of error B. Instantaneous error C. Derivative of error D. Actuator position

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The proportional law is uP=Kp e. The controller output changes immediately with the present error.

Q26. The main limitation of pure proportional control for many type-0 plants is:

A. It always gives infinite output B. It cannot respond to error C. Nonzero steady-state error can remain D. It has no adjustable gain

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: With finite proportional gain, a persistent demand or disturbance can require a nonzero error to generate the required control effort.

Q27. Integral action primarily responds to:

A. Future reference only B. Instantaneous error only C. Accumulated error over time D. Sensor resistance

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Integral action accumulates error. Persistent error therefore causes continuing change in controller output and can remove offset in suitable systems.

Q28. Derivative action primarily responds to:

A. Actuator position B. Magnitude of accumulated error C. Rate of change of error D. Supply voltage

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Derivative action is proportional to de/dt and therefore responds to how rapidly the error changes.

Q29. A PI controller combines:

A. Integral and derivative actions only B. Proportional and derivative actions C. Proportional and integral actions D. Derivative only

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PI control combines present-error correction with accumulated-error correction and is widely used where zero steady-state error is desired.

Q30. A PD controller is often used to:

A. Eliminate all sensor noise B. Guarantee zero steady-state error in every plant C. Improve transient response and damping without integral accumulation D. Store program memory

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PD adds derivative damping to proportional control. It does not generally remove steady-state error and avoids an integrator.

Q31. A PID controller contains:

A. Only P and D B. Only P and I C. P, I and D actions D. Only I and D

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PID combines proportional, integral and derivative actions to address present error, accumulated error and error trend.

Q32. Which PID term is especially sensitive to high-frequency measurement noise?

A. Proportional B. Integral C. Derivative D. Bias

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Differentiation amplifies high-frequency components, making the derivative term particularly sensitive to measurement noise.

Q33. Integral windup mainly occurs when:

A. Kp is zero B. The sensor is disconnected and derivative is zero C. The actuator saturates while the integral term continues accumulating error D. Sampling is infinite

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: When an actuator reaches its limit, additional integral demand cannot be applied. Continued accumulation can cause overshoot when the actuator leaves saturation.

Q34. Anti-windup methods are used to:

A. Disable feedback permanently B. Increase sensor noise C. Remove proportional action D. Limit or correct integral accumulation during actuator saturation

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Anti-windup techniques prevent excessive integral-state accumulation while the actuator is saturated.

Q35. Increasing proportional gain generally tends to:

A. Have no effect B. Always eliminate steady-state error C. Always slow response D. Reduce error but can increase overshoot and oscillation

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Higher Kp makes the loop more aggressive and can reduce error, but excessive gain can increase overshoot or cause oscillation.

Q36. Increasing integral gain generally tends to:

A. Reduce controller authority to zero B. Eliminate derivative noise C. Remove integral action D. Reduce steady-state error but can increase overshoot or oscillation

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Higher Ki strengthens accumulated-error correction, reducing offset but potentially reducing damping and stability margins.

Q37. Increasing derivative gain, when properly filtered, generally tends to:

A. Disable feedback B. Increase steady-state error directly C. Create integral windup D. Increase damping and reduce overshoot

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Derivative action responds to error slope and can improve damping. Excessive unfiltered derivative gain can amplify noise.

Q38. For negative feedback, error is commonly defined as:

A. Reference plus output B. Measured output minus controller gain C. Controller output minus reference D. Reference minus measured output

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: For a standard negative-feedback loop, e(t)=r(t)-y(t).

Q39. Negative feedback generally helps by:

A. Guaranteeing zero delay B. Making every system unstable C. Removing sensors D. Reducing sensitivity to some plant variations and disturbances

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Negative feedback compares output with reference and corrects deviations, often improving regulation and reducing sensitivity.

Q40. Derivative kick can occur when:

A. Plant has no inertia B. Integral gain is zero C. Actuator is disconnected D. Derivative action is applied directly to a sudden set-point change

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A sudden set-point step produces a sharp change in error, which can create a large derivative impulse. Derivative-on-measurement reduces this effect.

Q41. Derivative filtering is introduced mainly to:

A. Remove proportional gain B. Increase integral accumulation C. Increase actuator saturation D. Reduce amplification of measurement noise

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A practical derivative term is filtered to limit amplification of high-frequency measurement noise.

Q42. The term reset action traditionally refers to:

A. Feedforward action B. Derivative action C. Proportional action D. Integral action

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Reset is the traditional process-control term for integral action because it continues changing output while offset persists.

Q43. The term rate action traditionally refers to:

A. On-off action B. Integral action C. Proportional action D. Derivative action

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Rate action responds to the rate of change of error and corresponds to derivative control.

Q44. A controller output bias is useful because it:

A. Measures actuator speed B. Eliminates feedback C. Makes Kp infinite D. Provides a baseline control effort around which feedback corrections operate

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A bias or manual-reset value supplies the baseline output needed to maintain an operating point; feedback then makes corrections around it.

Q45. A two-position controller is also called:

A. Ratio controller B. PID controller C. Cascade controller D. On-off controller

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: An on-off controller switches between two output states according to error thresholds. It is simple but can cause cycling.

Q46. Hysteresis in an on-off controller is used mainly to:

A. Measure pressure B. Increase ADC resolution C. Create integral action D. Prevent rapid switching near the switching threshold

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Hysteresis provides separate ON and OFF thresholds, reducing chatter caused by noise or small fluctuations.

Q47. Cascade control uses:

A. Only manual control B. One sensor with no feedback C. Two actuators with no controller D. An inner control loop nested inside an outer loop

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Cascade control uses an outer loop whose controller sets the set point of an inner loop, allowing faster rejection of inner-loop disturbances.

Q48. Feedforward control differs from feedback because it:

A. Cannot use sensors B. Requires no model ever C. Uses only derivative action D. Acts using measured disturbance or process demand before the output error occurs

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Feedforward uses measured disturbance or demand to act proactively, whereas feedback reacts after an error is observed.

Q49. A PLC scan time is important because:

A. It eliminates I/O modules B. It determines HMI font size C. It sets hydraulic viscosity D. It limits how quickly the controller can detect and respond to events

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Scan time contributes to control latency. Very short events may be missed by ordinary scan-based inputs.

Q50. A digital PID controller requires:

A. No measurement B. Only a mechanical spring C. No clock D. Sampling, numerical computation and appropriate timing

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Digital PID evaluates sampled error at discrete intervals, so sampling period and execution timing affect performance.

Q51. A shorter sampling period generally provides:

A. Only slower response B. Guaranteed instability C. No change D. More frequent control updates, if computation and noise are properly managed

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A shorter sampling interval permits more frequent updates and better representation of process dynamics, provided noise and computation are properly managed.

Q52. Which controller is commonly selected when zero steady-state error is needed but derivative noise is undesirable?

A. P B. PD C. PI D. D

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PI combines proportional and integral action. Integral action removes steady-state offset without the explicit derivative term that is sensitive to noise.

Q53. Which controller can improve damping without introducing integral windup?

A. Relay B. I-only C. On-off D. PD

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: PD has proportional and derivative terms but no integrator, so integral windup is avoided while damping can be improved.

Q54. A very large proportional gain may cause:

A. Elimination of saturation B. Perfect stability C. Zero sensor noise D. Oscillation or instability for a sufficiently dynamic plant

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Closed-loop dynamics depend on gain and plant dynamics. Excessive proportional gain can reduce stability margins and cause oscillation or instability.

Q55. Derivative action is often applied to measured output rather than error to:

A. Remove all noise B. Increase windup C. Create open-loop control D. Reduce derivative kick caused by set-point changes

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Derivative-on-measurement avoids differentiating a sudden reference step and reduces derivative kick.

Q56. Controller tuning means:

A. Deleting feedback B. Replacing a sensor with a motor C. Changing supply voltage only D. Selecting controller parameters to achieve desired dynamic and steady-state performance

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Tuning selects controller parameters to meet requirements for stability, response speed, damping, steady-state error and robustness.

Q57. A stable closed-loop system generally has a response that:

A. Has infinite gain B. Is always zero C. Must be open-loop D. Remains bounded and settles appropriately under specified conditions

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Stability concerns boundedness and acceptable long-term behavior of the closed-loop response under specified conditions.

Q58. A PLC analog output is used when:

A. A controller must send a continuous command such as 0–10 V or 4–20 mA B. Only a push button is needed C. No actuator exists D. Only program memory is required

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Analog output modules convert digital controller values into standardized analog signals used to command valves, drives and other continuous actuators.

Q59. A 4–20 mA signal is useful in industrial instrumentation because:

A. It uses a live-zero convention and is relatively robust for long-distance transmission B. It requires no power C. It cannot detect loop faults D. It is purely mechanical

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The 4 mA live zero can distinguish a valid zero measurement from a zero-current condition, and current transmission is relatively robust over long cables.

Q60. Which register normally contains the address of the next instruction to be executed?

A. Stack pointer B. Program counter C. Status register D. Accumulator

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The program counter stores the address associated with the next instruction in the processor instruction sequence. The stack pointer instead identifies the current stack location.

Q61. The accumulator in a processor is commonly used for:

A. Temporary arithmetic and logical results B. Hydraulic pressure storage C. Sensor insulation D. PLC rack mounting

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: An accumulator is a processor register used to hold operands or intermediate results during arithmetic and logical operations.

Q62. A PLC interlock is primarily used to:

A. Prevent incompatible or unsafe operations from occurring simultaneously B. Increase CPU clock frequency C. Store analog values permanently D. Replace all sensors

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: An interlock imposes logical conditions that prevent conflicting or unsafe commands, such as simultaneous forward and reverse motor operation.

Q63. A PLC emergency-stop input should normally be arranged so that:

A. A defined stop condition removes the relevant operating permissive B. The PLC ignores the stop input C. The motor automatically restarts after power loss D. The stop signal is hidden

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: A stop condition should place the machine in a defined safe state. Safety-related emergency stopping normally requires appropriate safety-rated hardware and design.

Q64. Which microcontroller peripheral converts a digital code into an analog signal?

A. DAC B. ADC C. UART D. Timer

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: A digital-to-analog converter converts a digital numerical code into a corresponding analog voltage or current.

Q65. A UART communication frame commonly contains:

A. Start and stop bits around transmitted data B. Only a clock line C. A hydraulic accumulator D. A ladder rung

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: UART is asynchronous, so it normally uses start and stop bits to frame transmitted data. A separate clock line is not required.

Q66. Which controller action reacts directly to the present value of error?

A. Proportional B. Integral C. Derivative D. Reset

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Proportional action is directly proportional to the instantaneous error, uP=Kp e.

Q67. Which controller action can continue changing output because of accumulated past error?

A. Integral B. Proportional C. Derivative D. On-off

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Integral action depends on accumulated error, so its contribution represents the history of error rather than only its instantaneous value.

Q68. A derivative term can improve transient response because it:

A. Responds to the trend of error and can add damping B. Stores all past error C. Eliminates actuator saturation D. Creates another sensor

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Derivative action responds to error rate of change and can oppose rapid changes, thereby adding damping in suitable systems.

Q69. Which controller is generally unable to eliminate constant steady-state offset by itself in a typical type-0 plant?

A. Pure proportional control B. PI control C. PID control D. Integral control

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: With finite proportional gain, a constant load or reference demand generally requires a nonzero error to generate the required control effort. Integral action is normally added to remove the offset.

Q70. In a digital PI controller, integral action is normally implemented using:

A. Numerical accumulation of sampled error B. A mechanical spring C. A relay contact only D. A fixed resistor

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Digital integration is implemented by accumulating sampled error over successive control intervals, with the sampling period included in the numerical approximation.

Q71. A PLC analog input module is needed when a sensor provides:

A. A continuous signal such as 0–10 V or 4–20 mA B. Only a dry contact C. Only a mechanical key D. Only a ladder instruction

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Analog input modules condition and digitize continuous electrical signals so the PLC CPU can process the measured process variable.

Q72. A set point in a feedback control loop represents:

A. The desired value of the controlled variable B. The actuator maximum current only C. The PLC scan time D. The sensor cable length

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The set point is the target value. The controller compares it with the measured process variable to determine the control error.

Q73. Bumpless transfer between manual and automatic control aims to:

A. Avoid a sudden controller-output change during mode switching B. Increase derivative noise C. Disable feedback D. Force maximum actuator output

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Bumpless transfer matches the controller state or output to the current operating condition so switching modes does not produce a large output discontinuity.

Q74. Integral-state initialization is important at controller startup because:

A. The stored integral value directly affects the initial controller output B. It determines ADC resolution C. It replaces the plant model D. It sets the PLC clock

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The integral state contributes directly to controller output. Poor initialization can create an unwanted output bump at startup.

Q75. A PLC normally uses an input image table so that:

A. The program can process a consistent sampled state of inputs during a scan B. Analog signals need no conversion C. The CPU never reads inputs D. Outputs become sensors

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: In a conventional scan, physical inputs are sampled into an input image and the program executes using that consistent snapshot before outputs are updated.

Q76. A proportional controller has Kp=3 and an error of 4 units. Its proportional contribution is:

A. 12 units B. 7 units C. 1.33 units D. 0 units

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: uP=Kp e=3×4=12 units.

Q77. A PI controller has Kp=2, Ki=0.5 s^-1, e=4 and integral of error=6 unit-s. Output excluding bias is:

A. 5 B. 8 C. 11 D. 14

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: u=Kp e+Ki∫e dt=2×4+0.5×6=8+3=11.

Q78. A PID controller has Kp=1.5, Ki=0.2 s^-1, Kd=0.5 s, e=4, integral=10 and de/dt=2. Output excluding bias is:

A. 9 B. 8 C. 10.5 D. 12

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: u=1.5×4+0.2×10+0.5×2=6+2+1=9.

Q79. A 10-bit ADC has a 0–5 V range. Approximately what voltage increment corresponds to one LSB?

A. 4.88 mV B. 9.77 mV C. 19.53 mV D. 0.488 mV

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: There are 1024 codes. Approximate LSB=5/1024=0.004883 V=4.88 mV.

Q80. An 8-bit DAC has a 0–10 V range. Its approximate LSB size is:

A. 10 V B. 39.1 mV C. 78.1 mV D. 19.5 mV

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: There are 256 levels. Approximate step=10/256=0.03906 V=39.1 mV.

Q81. A PLC executes one scan in 10 ms. Approximately how many scans occur in one second?

A. 10 B. 50 C. 100 D. 200

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Scan frequency=1/0.010=100 scans/s.

Q82. A microcontroller clock is 20 MHz and one instruction cycle requires four clock periods. Instruction-cycle frequency is:

A. 5 MHz B. 20 MHz C. 80 MHz D. 4 MHz

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Instruction-cycle frequency=20/4=5 MHz.

Q83. A digital input pulse lasts 0.5 ms while PLC scan time is 2 ms and no high-speed input is used. Main risk is:

A. The event may be missed B. It will always be detected twice C. It becomes analog D. The CPU stops

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The pulse is shorter than the scan interval and may occur entirely between input-image updates.

Q84. A PWM controller applies 60% duty cycle to an ideal 24 V supply. Average voltage is approximately:

A. 9.6 V B. 12 V C. 14.4 V D. 24 V

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: For ideal PWM, average voltage≈DVs=0.60×24=14.4 V.

Q85. A proportional controller has Kp=4, error=2 V and bias=3 V. Output is:

A. 8 V B. 11 V C. 12 V D. 5 V

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Proportional contribution=4×2=8 V. Adding bias gives 11 V.

Q86. A PI controller has Kp=2, Ki=0.25 s^-1, constant error 5 for 8 s, and zero initial integral. Output excluding bias is:

A. 10 B. 15 C. 18 D. 20

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Proportional=2×5=10. Integral=0.25×5×8=10. Total=20.

Q87. A derivative controller has Kd=0.8 s. Error falls from 10 to 6 in 0.5 s. Derivative contribution is:

A. -6.4 B. -3.2 C. 3.2 D. 6.4

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: de/dt=(6−10)/0.5=−8 units/s. uD=0.8×−8=−6.4.

Q88. A 12-bit ADC uses a 0–3.3 V range. Approximate LSB size is:

A. 0.805 mV B. 1.61 mV C. 2.44 mV D. 3.30 mV

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: 4096 codes are available. LSB≈3.3/4096=0.0008057 V=0.806 mV.

Q89. A PLC output is updated at the end of a 5 ms scan. Ignoring other delays, maximum scan-related waiting time is approximately:

A. 0 ms B. 2.5 ms C. 5 ms D. 10 ms

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: An event just after an update may wait nearly one full scan for the next update, approximately 5 ms.

Q90. A controller output is limited to ±10 V. Computed PID output is +14 V. With hard saturation the actuator command is:

A. +4 V B. +10 V C. +14 V D. 0 V

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The actuator command is clipped at its physical maximum of +10 V.

Q91. Set point is 2 V and measured output is 1.5 V. With negative feedback, error r−y is:

A. -0.5 V B. 0.5 V C. 1.5 V D. 3.5 V

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: e=r−y=2−1.5=0.5 V.

Q92. An encoder generates 80 pulses/s. Pulse period is:

A. 5 ms B. 10 ms C. 12.5 ms D. 20 ms

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: T=1/f=1/80=0.0125 s=12.5 ms.

Q93. A 4–20 mA transmitter is scaled 0–100 bar. Pressure at 12 mA is:

A. 25 bar B. 40 bar C. 50 bar D. 75 bar

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Normalized current=(12−4)/(20−4)=0.5. Pressure=0.5×100=50 bar.

Q94. A 4–20 mA signal represents 0–200 °C. Temperature at 16 mA is:

A. 100 °C B. 125 °C C. 150 °C D. 175 °C

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Normalized current=(16−4)/16=0.75. Temperature=0.75×200=150 °C.

Q95. A PI controller has Kp=5. Using PB=100/Kp, proportional band is:

A. 5% B. 10% C. 20% D. 50%

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PB=100/5=20% under the common proportional-band definition.

Q96. A controller samples at 250 Hz. Sampling interval is:

A. 1 ms B. 2 ms C. 4 ms D. 8 ms

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: T=1/fs=1/250=0.004 s=4 ms.

Q97. A digital PID uses a 10 ms sampling period. Number of calculations in one minute is:

A. 600 B. 1000 C. 3000 D. 6000

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: There are 60/0.01=6000 control intervals in one minute.

Q98. A PLC has 16 digital inputs and 12 are ON. Percentage ON is:

A. 25% B. 50% C. 75% D. 80%

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: 12/16=0.75=75%.

Q99. A PID controller has Kp=2, Ki=0.5, Kd=1, e=3, integral=4 and de/dt=-1. Output excluding bias is:

A. 6 B. 7 C. 8 D. 9

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: u=2×3+0.5×4+1×(−1)=7.

Q100. A microcontroller outputs PWM at 25% duty cycle from an ideal 12 V supply. Average voltage is:

A. 3 V B. 6 V C. 9 V D. 12 V

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Average ideal PWM voltage≈0.25×12=3 V.