Q.1 What does a pH sensor in a bioreactor primarily measure?
Dissolved oxygen concentration
Acidity or alkalinity of the medium
Temperature of the culture
Pressure inside the vessel
Explanation - A pH sensor detects the hydrogen ion activity, indicating how acidic or basic the solution is.
Correct answer is: Acidity or alkalinity of the medium
Q.2 Which control strategy is most suitable for maintaining a constant temperature in a bioprocess?
On‑off control
PID control
Feed‑forward control
Cascade control
Explanation - PID control can continuously adjust heating/cooling power to keep temperature at the setpoint with minimal overshoot.
Correct answer is: PID control
Q.3 In a dissolved oxygen (DO) probe, which component is responsible for the electrochemical measurement?
Glass membrane
Platinum cathode
Thermistor
pH glass electrode
Explanation - The platinum cathode reacts with oxygen, generating a current proportional to the DO level.
Correct answer is: Platinum cathode
Q.4 What is the main purpose of a feed‑forward control loop in a bioprocess?
Correct past errors
Predict and compensate for known disturbances
Maintain constant pH
Regulate temperature
Explanation - Feed‑forward control acts on measured disturbances before they affect the process, improving response time.
Correct answer is: Predict and compensate for known disturbances
Q.5 Which of the following sensors is most commonly used to monitor biomass concentration in a fermenter?
Optical density sensor
Pressure transducer
Flow meter
Thermocouple
Explanation - Optical density (turbidity) correlates with cell concentration and is measured with a spectrophotometric sensor.
Correct answer is: Optical density sensor
Q.6 A 4‑20 mA current loop is used in industrial instrumentation because:
It provides high voltage levels
It is immune to signal loss over long distances
It can only transmit digital signals
It requires complex wiring
Explanation - Current loops maintain signal integrity over long cables, as the current is independent of resistance changes.
Correct answer is: It is immune to signal loss over long distances
Q.7 What does the term 'setpoint' refer to in process control?
The measured value of a variable
The desired target value for a process variable
The maximum allowable deviation
The speed of the controller
Explanation - A setpoint is the reference value the controller aims to maintain.
Correct answer is: The desired target value for a process variable
Q.8 Which type of actuator is typically used for opening and closing valves in a bioprocess plant?
Stepper motor
Pneumatic cylinder
Solenoid valve
Hydraulic pump
Explanation - Solenoid valves provide fast, reliable on/off control of fluid flow using electromagnetic actuation.
Correct answer is: Solenoid valve
Q.9 In a cascade control system, the primary controller:
Directly manipulates the final control element
Sets the setpoint for the secondary controller
Measures the secondary variable
Operates independently of the secondary loop
Explanation - Cascade control uses a primary loop to adjust the setpoint of a secondary loop for faster response.
Correct answer is: Sets the setpoint for the secondary controller
Q.10 Which instrument is used to measure the pressure inside a bioreactor?
Thermocouple
Manometer
pH electrode
Conductivity probe
Explanation - A manometer (or pressure transducer) measures the pressure difference inside the vessel.
Correct answer is: Manometer
Q.11 The main advantage of using a digital signal processor (DSP) in bioprocess control is:
Higher voltage handling
Faster real‑time computation of control algorithms
Reduced sensor accuracy requirements
Simpler wiring
Explanation - DSPs can execute complex control calculations quickly, enabling advanced strategies like model predictive control.
Correct answer is: Faster real‑time computation of control algorithms
Q.12 What does the acronym 'PLC' stand for?
Process Linear Controller
Programmable Logic Controller
Power Level Converter
Precision Lattice Chip
Explanation - A PLC is an industrial digital computer used for automation of electromechanical processes.
Correct answer is: Programmable Logic Controller
Q.13 In a bioprocess, which parameter is most directly affected by the agitation speed?
pH
Dissolved oxygen transfer
Temperature
Sterility
Explanation - Higher agitation improves mixing and oxygen transfer rates, crucial for aerobic cultures.
Correct answer is: Dissolved oxygen transfer
Q.14 Which type of sensor would you use to monitor the conductivity of a fermentation broth?
Ion‑selective electrode
Capacitive sensor
Conductivity probe
Thermistor
Explanation - Conductivity probes measure the ability of the solution to conduct electricity, indicating ionic strength.
Correct answer is: Conductivity probe
Q.15 A dead‑time in a control system refers to:
The time taken for the controller to compute an output
The delay between a change in the process variable and the observed effect on the measured variable
The period when the system is turned off
The time it takes for a sensor to calibrate
Explanation - Dead‑time (transport delay) can destabilize control loops if not accounted for.
Correct answer is: The delay between a change in the process variable and the observed effect on the measured variable
Q.16 Which control algorithm is best suited for a system that requires zero steady‑state error for step changes?
Proportional control only
Integral control only
Derivative control only
Proportional‑Integral (PI) control
Explanation - The integral term eliminates steady‑state error, while proportional provides responsiveness.
Correct answer is: Proportional‑Integral (PI) control
Q.17 In a SCADA system used for bioprocess monitoring, SCADA stands for:
Supervisory Control And Data Acquisition
Standard Control And Diagnostic Analyzer
Systematic Control And Device Automation
Signal Conversion And Data Aggregation
Explanation - SCADA provides real‑time monitoring and control across distributed equipment.
Correct answer is: Supervisory Control And Data Acquisition
Q.18 Which of the following is a non‑invasive method to estimate cell density in a bioreactor?
Sampling and plate counting
Optical sensor measuring back‑scattered light
Gravimetric dry weight measurement
Microscopic cell counting
Explanation - Optical sensors can infer cell density without removing samples, enabling continuous monitoring.
Correct answer is: Optical sensor measuring back‑scattered light
Q.19 A transducer that converts pressure into an electrical signal is called:
Actuator
Sensor
Transmitter
Controller
Explanation - A pressure transmitter outputs a proportional electrical signal representing pressure.
Correct answer is: Transmitter
Q.20 What is the main function of a PID controller's derivative term?
Reduce steady‑state error
Predict future error based on rate of change
Increase gain at low frequencies
Eliminate noise in the measurement
Explanation - The derivative term provides a damping action, improving stability and response speed.
Correct answer is: Predict future error based on rate of change
Q.21 Which of the following best describes a 'soft sensor' in bioprocessing?
A physical probe that directly measures a variable
A mathematical model that estimates a variable from other measurements
A sensor made of flexible material
A redundant sensor for safety
Explanation - Soft sensors use process data and algorithms to infer difficult‑to‑measure variables.
Correct answer is: A mathematical model that estimates a variable from other measurements
Q.22 Which safety instrumented system (SIS) function would automatically shut down a bioreactor if temperature exceeds a critical limit?
Alarm
Interlock
Shutdown
Bypass
Explanation - A shutdown function initiates a safe state to protect equipment and product when a hazardous condition is detected.
Correct answer is: Shutdown
Q.23 The term 'gain' in a control loop refers to:
The time delay between measurement and action
The ratio of output change to input change
The maximum allowable setpoint
The sensor's accuracy
Explanation - Gain quantifies how much the controller output responds to an error signal.
Correct answer is: The ratio of output change to input change
Q.24 In a bioprocess, the term 'sterile filtration' most commonly refers to:
Removing cells from the broth
Eliminating microbes using a 0.2 µm filter
Filtering out large particulates
Adjusting pH automatically
Explanation - 0.2 µm filters retain bacteria, providing a sterile final product.
Correct answer is: Eliminating microbes using a 0.2 µm filter
Q.25 Which communication protocol is widely used for industrial sensor networks in bioprocess plants?
Wi‑Fi
Bluetooth
Modbus
Zigbee
Explanation - Modbus is a robust, open protocol suitable for reliable data exchange in industrial environments.
Correct answer is: Modbus
Q.26 A 'deadband' in a control system is:
A region where no control action is taken to avoid frequent switching
The maximum error allowed before shutdown
The time taken for the controller to start
A safety limit for temperature
Explanation - Deadband prevents controller chatter by ignoring small deviations around the setpoint.
Correct answer is: A region where no control action is taken to avoid frequent switching
Q.27 When calibrating a pH sensor, the standard buffer solutions typically used are:
pH 4, pH 7, pH 10
pH 2, pH 5, pH 8
pH 1, pH 3, pH 9
pH 0, pH 6, pH 12
Explanation - These buffers cover acidic, neutral, and basic ranges for accurate calibration.
Correct answer is: pH 4, pH 7, pH 10
Q.28 Which instrument provides real‑time data on the rate of gas flow into a fermenter?
Mass flow meter
Thermometer
pH probe
Pressure gauge
Explanation - Mass flow meters measure the mass of gas per unit time, essential for controlling aeration.
Correct answer is: Mass flow meter
Q.29 In a temperature control loop, why is a thermocouple often preferred over a RTD for high‑temperature processes?
Higher accuracy
Faster response time
Lower cost
Both B and C
Explanation - Thermocouples respond quickly and are cheaper for high‑temperature applications, though RTDs are more accurate at lower ranges.
Correct answer is: Both B and C
Q.30 The term 'hysteresis' in sensor behavior refers to:
Delay in signal transmission
Different output values for increasing vs. decreasing input
Signal amplification
Temperature dependence of the sensor
Explanation - Hysteresis causes a lag between input changes and sensor output, leading to error.
Correct answer is: Different output values for increasing vs. decreasing input
Q.31 Which type of valve provides precise control over flow rate in a bioprocess?
Gate valve
Butterfly valve
Globe valve
Ball valve
Explanation - Globe valves have a linear flow characteristic, enabling fine flow regulation.
Correct answer is: Globe valve
Q.32 A bioreactor equipped with a 'peristaltic pump' is mainly used for:
Measuring temperature
Providing sterile air
Delivering precise liquid feeds
Regulating pressure
Explanation - Peristaltic pumps move fluid by compressing flexible tubing, ensuring sterile and accurate dosing.
Correct answer is: Delivering precise liquid feeds
Q.33 In the context of process control, 'robustness' means:
The ability to operate at high speeds
Resistance to disturbances and model uncertainties
Having a large physical size
Using expensive components
Explanation - A robust controller maintains performance despite variations and unknowns.
Correct answer is: Resistance to disturbances and model uncertainties
Q.34 Which of the following is a typical output of a bioprocess data historian?
Real‑time alarm messages
Long‑term trend graphs
Control algorithm code
Physical sensor hardware
Explanation - Historians store process data over time, enabling analysis and trend visualization.
Correct answer is: Long‑term trend graphs
Q.35 A 'gain scheduling' technique is used when:
The process dynamics change with operating conditions
The controller needs to be shut down
The sensor is offline
The setpoint is constant
Explanation - Gain scheduling adjusts controller parameters based on the current operating point.
Correct answer is: The process dynamics change with operating conditions
Q.36 Which sensor would you select to detect foam formation on the surface of a culture broth?
Capacitive foam sensor
Thermocouple
pH electrode
Dissolved oxygen probe
Explanation - Capacitive sensors detect changes in dielectric properties caused by foam on the liquid surface.
Correct answer is: Capacitive foam sensor
Q.37 In a bioprocess control system, the term 'actuator' refers to:
Device that measures a variable
Software algorithm for control
Component that moves a valve or motor to affect the process
Communication protocol
Explanation - Actuators convert control signals into physical action on the process.
Correct answer is: Component that moves a valve or motor to affect the process
Q.38 What is the primary purpose of an anti‑whirl device in a stirred‑tank bioreactor?
Increase mixing efficiency
Prevent excessive vibration of the impeller
Reduce temperature gradients
Control pH automatically
Explanation - Anti‑whirl devices dampen oscillations, protecting equipment and ensuring stable operation.
Correct answer is: Prevent excessive vibration of the impeller
Q.39 Which type of control loop would you use to maintain a constant oxygen transfer rate (OTR) in a high‑density fermentation?
Temperature control loop
Cascade control loop with aeration and agitation as secondary variables
Single‑loop on‑off control
Feed‑forward only control
Explanation - OTR depends on both aeration and agitation; cascade control can manage both to keep OTR steady.
Correct answer is: Cascade control loop with aeration and agitation as secondary variables
Q.40 A 'smart sensor' differs from a traditional sensor because it:
Requires no power supply
Includes onboard processing and communication capabilities
Measures only temperature
Is always wireless
Explanation - Smart sensors can preprocess data, self‑diagnose, and communicate using digital protocols.
Correct answer is: Includes onboard processing and communication capabilities
Q.41 Which of the following is a common cause of drift in pH sensor readings?
Battery voltage fluctuation
Temperature changes only
Electrode aging and membrane fouling
Air bubbles in the reference electrode
Explanation - Over time, the glass membrane and reference electrode degrade, causing drift.
Correct answer is: Electrode aging and membrane fouling
Q.42 The Nyquist plot is used in control engineering to assess:
Sensor calibration curves
System stability and phase margin
Temperature distribution
Flow rate accuracy
Explanation - Nyquist plots represent frequency response, helping determine stability margins.
Correct answer is: System stability and phase margin
Q.43 In a bioprocess, the term 'lag phase' refers to:
Time when cells adapt before exponential growth
Delay in sensor response
Time required for temperature equilibration
Period of sterilization
Explanation - Lag phase is a biological concept, not a control term, but important for setpoint planning.
Correct answer is: Time when cells adapt before exponential growth
Q.44 Which method is most suitable for reducing noise in a sensor signal before it enters the controller?
Increasing the gain
Applying a low‑pass filter
Using a higher sampling rate
Adding more sensors
Explanation - Low‑pass filters attenuate high‑frequency noise while preserving the desired signal.
Correct answer is: Applying a low‑pass filter
Q.45 A 'redundant sensor' arrangement improves:
Cost efficiency
System safety and reliability
Sensor speed
Data storage capacity
Explanation - Redundancy allows cross‑checking and fault detection, enhancing reliability.
Correct answer is: System safety and reliability
Q.46 Which of the following is NOT a typical alarm condition in a bioprocess control system?
pH out of range
Temperature exceeds limit
Valve position unknown
Sensor cable length
Explanation - Alarm conditions are related to process variables; cable length is a design parameter, not an alarm.
Correct answer is: Sensor cable length
Q.47 In a distributed control system (DCS), the term 'node' usually refers to:
A physical sensor
A programmable controller or I/O module
The main power supply
The software user interface
Explanation - Nodes are individual processing units within the DCS network.
Correct answer is: A programmable controller or I/O module
Q.48 Which parameter is most critical for determining the scale‑up factor when moving from lab‑scale to pilot‑scale bioreactors?
Impeller diameter
Oxygen transfer coefficient (kLa)
Glass thickness
Color of the vessel
Explanation - kLa dictates oxygen availability; matching it ensures similar cellular environments across scales.
Correct answer is: Oxygen transfer coefficient (kLa)
Q.49 A 'process variable' (PV) in control engineering is:
The desired setpoint value
The measured value of a controlled variable
The output of the controller
The algorithm used by the controller
Explanation - PV is the real‑time measurement fed back to the controller.
Correct answer is: The measured value of a controlled variable
Q.50 What is the main advantage of using a 'model predictive controller' (MPC) in bioprocesses?
Simpler hardware requirements
Ability to anticipate future disturbances using a process model
Faster response than any other controller
No need for sensor calibration
Explanation - MPC uses a dynamic model to predict future behavior and optimize control moves.
Correct answer is: Ability to anticipate future disturbances using a process model
Q.51 Which type of sensor uses a membrane that changes resistance with moisture content?
Capacitive humidity sensor
Resistive humidity sensor
Thermocouple
pH electrode
Explanation - Resistive sensors detect humidity by the change in electrical resistance of a hygroscopic material.
Correct answer is: Resistive humidity sensor
Q.52 When a bioprocess control system experiences 'integral windup', the likely cause is:
Controller gain too low
Actuator saturation limiting output
Sensor noise
High sampling frequency
Explanation - When the actuator cannot follow the controller output, the integral term accumulates excessively.
Correct answer is: Actuator saturation limiting output
Q.53 A 'batch' bioprocess differs from a 'continuous' process primarily in:
The type of sensors used
The operation mode—fixed time vs. steady‑state operation
The need for temperature control
The presence of pH control
Explanation - Batch processes run for a set period; continuous processes maintain a steady state with ongoing feed and removal.
Correct answer is: The operation mode—fixed time vs. steady‑state operation
Q.54 In a PID controller, the term 'tuning' refers to:
Changing the sensor hardware
Adjusting the proportional, integral, and derivative gains
Rewiring the wiring diagram
Increasing the sampling rate
Explanation - Tuning optimizes the PID parameters to achieve desired response characteristics.
Correct answer is: Adjusting the proportional, integral, and derivative gains
Q.55 Which of the following best describes a 'zero‑order hold' in digital control systems?
A method that keeps the output constant between sampling intervals
A technique that integrates the error over time
A filter that removes high‑frequency noise
A sensor that measures zero offset
Explanation - Zero‑order hold maintains the last computed control signal until the next sample.
Correct answer is: A method that keeps the output constant between sampling intervals
Q.56 When implementing a safety interlock for a sterilization step, the interlock should be activated if:
Temperature reaches the sterilization setpoint
The door is opened during heating
The pH is stable
The flow meter reads zero
Explanation - Opening the door compromises sterility; the interlock prevents operation under unsafe conditions.
Correct answer is: The door is opened during heating
Q.57 What is the purpose of a 'bias' setting in a sensor's signal conditioning circuit?
To amplify the signal
To offset the signal to a desired range
To filter out noise
To increase the sensor's lifespan
Explanation - Bias adds a fixed voltage or current, shifting the signal into the usable range of the ADC.
Correct answer is: To offset the signal to a desired range
Q.58 Which of the following statements about 'soft PLCs' is true?
They are hardware‑based only
They run control logic on standard computers
They cannot communicate with field devices
They replace all sensors
Explanation - Soft PLCs use software on PCs to execute PLC programs, offering flexibility and scalability.
Correct answer is: They run control logic on standard computers
Q.59 In a bioprocess, the term 'kLa' is used to describe:
Mass transfer coefficient for oxygen
Heat transfer coefficient
Viscosity of the broth
pH buffering capacity
Explanation - kLa quantifies the rate at which oxygen transfers from gas to liquid phase.
Correct answer is: Mass transfer coefficient for oxygen
Q.60 Which communication protocol is specifically designed for real‑time industrial automation and is widely used in motion control?
Ethernet/IP
PROFINET
CANopen
Modbus TCP
Explanation - CANopen provides deterministic communication suitable for real‑time control applications.
Correct answer is: CANopen
Q.61 A 'batch reactor' with an automated sampling system typically uses which type of valve for sterile sampling?
Globe valve
Needle valve
Stainless‑steel valve with a sterile filter
Butterfly valve
Explanation - These valves maintain sterility while allowing sample extraction.
Correct answer is: Stainless‑steel valve with a sterile filter
Q.62 When calibrating a temperature sensor, the term 'offset error' refers to:
A constant difference between measured and actual temperature
A variation that changes with temperature
Noise in the sensor signal
Delay in sensor response
Explanation - Offset error is a fixed bias that can be corrected by adjusting the sensor output.
Correct answer is: A constant difference between measured and actual temperature
Q.63 What does the term 'dead‑time compensation' aim to improve in a control loop?
Sensor accuracy
Response speed and stability
Power consumption
Physical size of the controller
Explanation - Compensating for dead‑time reduces overshoot and improves stability.
Correct answer is: Response speed and stability
Q.64 In a bioprocess, which sensor is most appropriate for monitoring the concentration of a specific substrate like glucose?
pH electrode
Near‑infrared (NIR) spectroscopy sensor
Thermocouple
Pressure transducer
Explanation - NIR can be calibrated to quantify specific chemical concentrations non‑invasively.
Correct answer is: Near‑infrared (NIR) spectroscopy sensor
Q.65 A 'setpoint tracking' controller is primarily used for:
Maintaining a constant temperature
Following a predefined trajectory over time
Detecting sensor faults
Increasing the gain of the system
Explanation - Setpoint tracking adjusts the setpoint dynamically according to a schedule or recipe.
Correct answer is: Following a predefined trajectory over time
Q.66 Which factor most directly affects the accuracy of a flow meter in a liquid feed line?
Pipe diameter variations
Ambient temperature
Electrical noise
Color of the fluid
Explanation - Changes in pipe diameter alter flow profile, impacting measurement accuracy.
Correct answer is: Pipe diameter variations
Q.67 The term 'process analytical technology' (PAT) in bioprocessing emphasizes:
Manual sampling and analysis
Real‑time monitoring and control of critical quality attributes
Post‑process product testing only
Reducing the number of sensors
Explanation - PAT integrates sensors, models, and control to ensure product quality during manufacturing.
Correct answer is: Real‑time monitoring and control of critical quality attributes
Q.68 Which of the following is a typical cause of sensor 'bias drift' over long operation periods?
Changes in ambient light
Electrode fouling
Power supply voltage fluctuation
All of the above
Explanation - Various environmental and hardware factors can cause gradual shifts in sensor output.
Correct answer is: All of the above
Q.69 In a distributed control system, a 'redundant controller' architecture provides:
Higher processing speed
Backup control capability if the primary controller fails
Lower cost
Simpler wiring
Explanation - Redundant controllers ensure continuous operation by taking over if one fails.
Correct answer is: Backup control capability if the primary controller fails
Q.70 Which of the following sensors would be unsuitable for measuring temperature in a high‑pressure steam sterilization step?
Thermocouple
RTD
Infrared pyrometer
Capacitive humidity sensor
Explanation - Humidity sensors cannot survive high‑temperature, high‑pressure steam environments.
Correct answer is: Capacitive humidity sensor
Q.71 A 'process deadband' of ±0.5 °C in temperature control is used to:
Increase the controller's response speed
Prevent frequent on/off cycling of the heating/cooling system
Reduce sensor accuracy
Allow the temperature to drift far from the setpoint
Explanation - Deadband creates a tolerance zone, reducing wear on actuators.
Correct answer is: Prevent frequent on/off cycling of the heating/cooling system
Q.72 The main advantage of using a 'digital twin' in bioprocess engineering is:
Eliminating the need for sensors
Providing a virtual replica for simulation, optimization, and predictive control
Reducing the physical size of the reactor
Increasing the power consumption
Explanation - Digital twins enable testing control strategies virtually before applying them to the real system.
Correct answer is: Providing a virtual replica for simulation, optimization, and predictive control
Q.73 In a feedback control loop, the term 'loop gain' is defined as:
The product of controller gain and process gain
The speed of the actuator
The sampling frequency
The maximum sensor range
Explanation - Loop gain determines overall system responsiveness and stability.
Correct answer is: The product of controller gain and process gain
Q.74 Which of the following is a common method to ensure sterile connections between bioreactor and downstream equipment?
Using rubber gaskets
Applying silicone grease
Using sterile welding (e.g., welded tubing) or sterile quick‑connects
Taping the connections
Explanation - Sterile welding or aseptic connectors maintain sterility during transfer.
Correct answer is: Using sterile welding (e.g., welded tubing) or sterile quick‑connects
Q.75 The term 'Bode plot' is used to analyze:
Time‑domain sensor drift
Frequency response (gain and phase) of a control system
Temperature distribution in a reactor
Chemical composition of the broth
Explanation - Bode plots help assess stability margins and design controllers.
Correct answer is: Frequency response (gain and phase) of a control system
Q.76 Which of the following is most appropriate for measuring very low dissolved oxygen levels (<0.5 mg/L) in a bioreactor?
Clark‑type electrochemical probe
Optical (luminescence) DO sensor
Thermocouple
pH electrode
Explanation - Optical sensors have higher sensitivity and lower drift at low DO concentrations.
Correct answer is: Optical (luminescence) DO sensor
Q.77 In a bioprocess, the term 'specific growth rate' (µ) is measured in:
g/L·h
h⁻¹
°C
mL/min
Explanation - Specific growth rate describes the exponential growth per unit time.
Correct answer is: h⁻¹
Q.78 Which control strategy is best suited for a process where the measured variable must never exceed a safety limit?
PID control
On‑off control with a hard limit
Cascade control
Feed‑forward control
Explanation - A hard limit (safety interlock) ensures the variable cannot surpass the critical threshold.
Correct answer is: On‑off control with a hard limit
Q.79 When a sensor signal is digitized using an analog‑to‑digital converter (ADC), the term 'resolution' refers to:
The speed of conversion
The smallest change in input that can be distinguished
The voltage range of the sensor
The power consumption of the ADC
Explanation - Resolution determines how finely the analog signal is quantized.
Correct answer is: The smallest change in input that can be distinguished
Q.80 A 'pneumatic actuator' in a bioprocess control system is powered by:
Electric current
Compressed air
Hydraulic fluid
Magnetic fields
Explanation - Pneumatic actuators use pressurized air to move mechanical components.
Correct answer is: Compressed air
Q.81 Which parameter is most directly influenced by the impeller design (e.g., Rushton vs. marine) in a stirred‑tank bioreactor?
pH stability
Oxygen transfer rate
Temperature uniformity
Foam formation
Explanation - Impeller geometry affects mixing intensity and gas dispersion, impacting kLa.
Correct answer is: Oxygen transfer rate
Q.82 In the context of bioprocess instrumentation, 'calibration curve' is used to:
Determine sensor lifespan
Convert raw sensor output to engineering units
Adjust the control algorithm gains
Measure process dead‑time
Explanation - A calibration curve maps sensor readings (e.g., voltage) to known values of the measured variable.
Correct answer is: Convert raw sensor output to engineering units
Q.83 Which of the following best describes a 'process variable' that is considered 'controlled' rather than 'manipulated'?
Valve opening percentage
Temperature setpoint
Measured pH value
Controller output signal
Explanation - The pH value is observed (PV) and the controller manipulates an input (e.g., acid/base addition) to control it.
Correct answer is: Measured pH value
Q.84 A 'soft sensor' estimating biomass concentration from dissolved oxygen and CO₂ data would be an example of:
Model‑based estimation
Direct measurement
Redundant sensing
Calibration drift
Explanation - The soft sensor uses a mathematical model linking DO and CO₂ to biomass.
Correct answer is: Model‑based estimation
Q.85 Which of the following is a typical cause for a sudden drop in dissolved oxygen reading during a fermentation run?
Increase in agitation speed
Sensor fouling or membrane blockage
Decrease in temperature
Addition of buffer solution
Explanation - Fouling reduces sensor sensitivity, causing an apparent drop in DO.
Correct answer is: Sensor fouling or membrane blockage
Q.86 The term 'PID auto‑tuning' refers to:
Manually adjusting gains by trial and error
Using an algorithm that automatically determines optimal PID parameters
Increasing the sampling frequency
Replacing the controller with a PLC
Explanation - Auto‑tuning simplifies controller setup by analyzing process response.
Correct answer is: Using an algorithm that automatically determines optimal PID parameters
Q.87 In a bioprocess control system, the term 'HMI' stands for:
Human‑Machine Interface
High‑Memory Interface
Hybrid Modulation Input
Hydraulic Motor Integration
Explanation - HMI provides operators with visualisation and control capabilities.
Correct answer is: Human‑Machine Interface
Q.88 When implementing a 'cascade control' for temperature and agitation, which variable is typically the primary loop?
Agitation speed
Reactor temperature
pH
Dissolved oxygen
Explanation - Temperature is the main controlled variable; agitation acts as a secondary variable to improve temperature control.
Correct answer is: Reactor temperature
Q.89 A 'zero‑order hold' in a digital control system is used to:
Eliminate dead‑time
Maintain the last computed control output until the next sample
Increase sensor resolution
Provide power to the actuator
Explanation - Zero‑order hold keeps the output constant between sampling instants.
Correct answer is: Maintain the last computed control output until the next sample
Q.90 Which sensor type is typically used for measuring the concentration of dissolved gases like CO₂ in a bioreactor?
Electrochemical sensor
Optical (NIR) sensor
Capacitive humidity sensor
Thermistor
Explanation - Electrochemical sensors can selectively measure dissolved gases based on diffusion through a membrane.
Correct answer is: Electrochemical sensor
Q.91 What is the main purpose of a 'process safety valve' in a bioreactor system?
Regulate temperature
Prevent over‑pressure conditions
Control pH
Measure flow rate
Explanation - Safety valves release excess pressure to protect equipment and maintain safety.
Correct answer is: Prevent over‑pressure conditions
Q.92 In a bioprocess, the term 'feed‑forward' control is distinguished from feedback control by:
Acting on measured disturbances before they affect the process
Using only historical data
Adjusting the setpoint only after the error occurs
Operating without any sensors
Explanation - Feed‑forward uses disturbance measurements to pre‑emptively correct the process.
Correct answer is: Acting on measured disturbances before they affect the process
Q.93 Which of the following best describes the function of a 'process analytical technology' (PAT) sensor network?
To replace all human operators
To provide real‑time data for process monitoring and control
To increase the physical size of the plant
To reduce the number of sensors required
Explanation - PAT integrates sensors and data analytics to ensure product quality during manufacturing.
Correct answer is: To provide real‑time data for process monitoring and control
Q.94 A 'dead‑time' of 2 seconds in an oxygen control loop can lead to:
Faster response
Increased overshoot and possible instability
Reduced sensor drift
Elimination of steady‑state error
Explanation - Dead‑time introduces a lag that can cause the controller to over‑react, destabilizing the loop.
Correct answer is: Increased overshoot and possible instability
Q.95 Which sensor technology is most appropriate for online measurement of cell viability (live/dead ratio) in a bioreactor?
Fluorescence‑based optical sensor
pH electrode
Thermocouple
Pressure transducer
Explanation - Fluorescent dyes can differentiate live and dead cells, enabling real‑time viability monitoring.
Correct answer is: Fluorescence‑based optical sensor
Q.96 In a control loop, the term 'integral action' primarily helps to:
Reduce response speed
Eliminate steady‑state error
Increase noise sensitivity
Prevent actuator saturation
Explanation - The integral term accumulates error over time, driving the steady‑state error to zero.
Correct answer is: Eliminate steady‑state error
Q.97 Which of the following is a typical method for ensuring the sterility of a sampling line in a fed‑batch bioprocess?
Using a silicone tube
Applying a sterile filter in the line
Leaving the line open to air
Connecting directly to the reactor wall
Explanation - Sterile filters prevent microorganisms from entering the sampling line while allowing fluid passage.
Correct answer is: Applying a sterile filter in the line
Q.98 When a bioprocess control system uses a 'watchdog timer', its purpose is to:
Measure temperature
Detect controller software failure and trigger a safe shutdown
Increase the sampling rate
Adjust sensor gain
Explanation - Watchdog timers monitor system health and ensure safe actions if the controller becomes unresponsive.
Correct answer is: Detect controller software failure and trigger a safe shutdown
Q.99 A 'process variable' of 2 g/L biomass concentration is measured. If the setpoint is 3 g/L, the error signal for a proportional controller is:
1 g/L
−1 g/L
2 g/L
0 g/L
Explanation - Error = Setpoint − Measured = 3 g/L − 2 g/L = 1 g/L.
Correct answer is: 1 g/L
Q.100 In a bioprocess, a 'soft sensor' can be used to estimate which variable when a physical sensor is unavailable?
Temperature
pH
Biomass concentration
Pressure
Explanation - Soft sensors combine measurable variables (e.g., DO, CO₂) with models to estimate biomass.
Correct answer is: Biomass concentration
Q.101 Which of the following is a key benefit of using a 'distributed control system' (DCS) over a single PLC in large bioprocess plants?
Lower initial cost
Scalability and modularity
Simpler programming language
Elimination of sensors
Explanation - DCS can manage many control loops across dispersed equipment, making expansion easier.
Correct answer is: Scalability and modularity
Q.102 When calibrating a flow meter, the term 'zero‑flow offset' refers to:
The flow rate at maximum pressure
The reading shown when there is no flow
The temperature correction factor
The sensor's response time
Explanation - Zero‑flow offset is the baseline reading that must be subtracted from actual measurements.
Correct answer is: The reading shown when there is no flow
Q.103 A 'deadband' of ±5 % in a valve position controller helps to:
Increase valve wear
Prevent frequent small adjustments (chattering)
Improve sensor accuracy
Reduce dead‑time
Explanation - Deadband creates a tolerance zone, reducing unnecessary valve actuation.
Correct answer is: Prevent frequent small adjustments (chattering)
Q.104 In the context of bioprocess instrumentation, 'signal conditioning' typically involves:
Amplifying, filtering, and converting sensor signals to a suitable format
Cleaning the bioreactor
Increasing the reactor volume
Sterilizing the sensors
Explanation - Signal conditioning prepares raw sensor data for accurate acquisition and control.
Correct answer is: Amplifying, filtering, and converting sensor signals to a suitable format
Q.105 Which type of controller is most suitable for a process that requires rapid correction of small disturbances with minimal overshoot?
On‑off controller
PID controller with well‑tuned derivative action
Integral‑only controller
Feed‑forward controller only
Explanation - Derivative action damps rapid changes, reducing overshoot while maintaining fast response.
Correct answer is: PID controller with well‑tuned derivative action
Q.106 A 'process analytical technology' (PAT) initiative would most likely include which of the following activities?
Manual off‑line sampling every hour
Real‑time spectroscopic monitoring of substrate concentration
Eliminating all sensors to save cost
Increasing the size of the bioreactor
Explanation - PAT focuses on inline, real‑time measurement to control critical quality attributes.
Correct answer is: Real‑time spectroscopic monitoring of substrate concentration
Q.107 Which of the following is a common cause for a sudden increase in reactor temperature during fermentation?
Decrease in agitation
Microbial heat generation due to high metabolic activity
Cooling system failure only
Addition of cold water
Explanation - Active cells produce metabolic heat, raising temperature if not removed.
Correct answer is: Microbial heat generation due to high metabolic activity
Q.108 In a bioprocess control loop, the term 'actuator saturation' means:
The sensor has reached its maximum reading
The actuator cannot provide more output beyond its limit
The controller is offline
The process variable is zero
Explanation - Saturation occurs when the actuator is at its physical maximum/minimum, limiting control action.
Correct answer is: The actuator cannot provide more output beyond its limit
Q.109 Which of the following is NOT a typical component of a SCADA system in bioprocess monitoring?
RTU (Remote Terminal Unit)
HMI (Human‑Machine Interface)
PLC (Programmable Logic Controller)
Centrifuge
Explanation - Centrifuges are equipment, not a software/hardware component of SCADA.
Correct answer is: Centrifuge
Q.110 A 'process dead time' of 5 seconds can be reduced by:
Increasing the sensor sampling rate
Using a faster actuator
Implementing a dead‑time compensator in the controller
All of the above
Explanation - Higher sampling, faster actuation, and compensation algorithms all help mitigate dead‑time effects.
Correct answer is: All of the above
Q.111 In a fed‑batch bioprocess, the feed rate is typically adjusted based on:
Time elapsed only
Measured substrate concentration and growth rate
Color of the broth
Ambient humidity
Explanation - Feed rate control uses real‑time measurements to avoid substrate inhibition or limitation.
Correct answer is: Measured substrate concentration and growth rate
Q.112 Which of the following best describes the function of a 'process historian'?
Real‑time alarm generation
Long‑term data storage for trend analysis
Control algorithm execution
Physical actuation of valves
Explanation - Historians archive process data, enabling post‑run analysis and compliance reporting.
Correct answer is: Long‑term data storage for trend analysis
Q.113 A 'pneumatic valve' in a bioprocess control system is primarily actuated by:
Electric current
Compressed air
Hydraulic fluid
Magnetic field
Explanation - Pneumatic valves use pressurized air to open or close.
Correct answer is: Compressed air
Q.114 When a sensor's output shows a constant offset from the true value, the error is called:
Gain error
Offset error
Linearity error
Hysteresis
Explanation - Offset error is a fixed bias added to all measurements.
Correct answer is: Offset error
Q.115 In a bioprocess, the term 'specific oxygen uptake rate' (qO₂) is expressed in:
mmol O₂·g⁻¹ h⁻¹
g/L·h
°C
L/min
Explanation - qO₂ quantifies oxygen consumption per unit biomass per hour.
Correct answer is: mmol O₂·g⁻¹ h⁻¹
Q.116 Which of the following is a typical characteristic of an 'on‑off' controller?
Continuous variable output
Smooth response with no overshoot
Binary output (full on or full off)
Integral action only
Explanation - On‑off controllers switch fully between two states, like a thermostat.
Correct answer is: Binary output (full on or full off)
Q.117 The main purpose of a 'redundant sensor' configuration is to:
Increase measurement speed
Provide backup and fault detection
Reduce power consumption
Simplify wiring
Explanation - Redundant sensors allow comparison to detect failures and ensure reliability.
Correct answer is: Provide backup and fault detection
Q.118 Which sensor technology uses a light‑emitting diode (LED) and a photodetector to measure turbidity?
Thermocouple
Optical density sensor
Capacitive humidity sensor
Pressure transducer
Explanation - OD sensors emit light and detect scattered light to infer cell concentration.
Correct answer is: Optical density sensor
Q.119 In a bioprocess, a 'feed‑forward' controller would most likely use which measurement as its input?
Measured temperature
Predicted substrate consumption rate
pH reading
Valve position
Explanation - Feed‑forward uses a model of expected disturbances (e.g., substrate uptake) to adjust the feed before the effect appears.
Correct answer is: Predicted substrate consumption rate
Q.120 What is the primary function of a 'mass flow controller' (MFC) in a bioprocess?
Measure temperature
Regulate the mass flow rate of gases or liquids precisely
Control pH
Detect foam formation
Explanation - MFCs provide accurate, programmable flow rates essential for aeration and feed delivery.
Correct answer is: Regulate the mass flow rate of gases or liquids precisely
Q.121 When a control system experiences 'integral windup', a common mitigation technique is:
Increasing the proportional gain
Implementing an anti‑windup scheme that limits the integral term
Reducing sensor sampling frequency
Using a slower actuator
Explanation - Anti‑windup prevents the integral term from accumulating excessively when the actuator is saturated.
Correct answer is: Implementing an anti‑windup scheme that limits the integral term
Q.122 In a bioprocess, the term 'kLa' is used to describe:
Heat transfer coefficient
Mass transfer coefficient for oxygen
Viscosity of the broth
pH buffering capacity
Explanation - kLa quantifies the rate of oxygen transfer from gas to liquid phase.
Correct answer is: Mass transfer coefficient for oxygen
Q.123 A 'soft PLC' differs from a traditional PLC mainly because:
It runs control logic on general‑purpose computers
It cannot communicate with field devices
It is only used for HVAC systems
It uses analog signals exclusively
Explanation - Soft PLCs use software on PCs, offering flexibility and easy integration with IT systems.
Correct answer is: It runs control logic on general‑purpose computers
Q.124 Which of the following is a typical indicator that a bioreactor's pH control loop is poorly tuned?
Steady pH at setpoint with no oscillation
Large, sustained oscillations around the setpoint
Slow response with no overshoot
Constant valve position
Explanation - Underdamped or overly aggressive tuning leads to oscillatory behavior.
Correct answer is: Large, sustained oscillations around the setpoint
Q.125 In a bioprocess, an 'air sparger' primarily contributes to:
Mixing the broth
Increasing dissolved oxygen by creating bubbles
Cooling the reactor
Measuring pH
Explanation - Air spargers inject gas, enhancing oxygen transfer to the liquid phase.
Correct answer is: Increasing dissolved oxygen by creating bubbles
Q.126 Which of the following best explains why a 'low‑pass filter' is used on sensor signals before they enter a controller?
To amplify high‑frequency noise
To remove high‑frequency noise and retain the low‑frequency signal
To increase sensor range
To convert analog signals to digital
Explanation - Low‑pass filters smooth out rapid fluctuations that could cause control instability.
Correct answer is: To remove high‑frequency noise and retain the low‑frequency signal
Q.127 A 'process variable' (PV) is measured at 5 °C while the setpoint is 6 °C. If the controller uses proportional gain of 2, what is the controller output (ignoring other terms)?
2 units
−2 units
1 unit
−1 unit
Explanation - Error = 6 °C – 5 °C = 1 °C; Output = Kp × Error = 2 × 1 = 2 units (positive output to increase temperature).
Correct answer is: 2 units
Q.128 Which communication protocol is most suitable for high‑speed, deterministic data exchange in a bioprocess control network?
Modbus RTU
Ethernet/IP
PROFINET IRT (Isochronous Real‑Time)
Wi‑Fi
Explanation - PROFINET IRT provides deterministic timing required for fast control loops.
Correct answer is: PROFINET IRT (Isochronous Real‑Time)
Q.129 In a bioprocess, which parameter is directly linked to the need for antifoam addition?
pH drift
Excessive foam formation due to high gas flow
Temperature spikes
Low dissolved oxygen
Explanation - Foam can block spargers and sensors; antifoam reduces surface stability.
Correct answer is: Excessive foam formation due to high gas flow
Q.130 Which of the following best defines 'robust control'?
Control that works only under ideal conditions
Control that maintains performance despite model uncertainties and disturbances
Control with the highest possible gain
Control that requires no tuning
Explanation - Robust control ensures stability and performance even when the process varies.
Correct answer is: Control that maintains performance despite model uncertainties and disturbances
Q.131 A 'temperature sensor' that outputs a voltage proportional to temperature (e.g., 10 mV/°C) is known as:
Thermistor
Thermocouple
RTD
Thermopile
Explanation - Thermopiles generate a voltage proportional to temperature differences.
Correct answer is: Thermopile
Q.132 Which type of sensor is most appropriate for detecting the presence of organic solvents in exhaust gas streams?
Electrochemical gas sensor
Thermocouple
Capacitive humidity sensor
pH electrode
Explanation - Electrochemical sensors can be tailored to detect specific volatile organic compounds.
Correct answer is: Electrochemical gas sensor
Q.133 In a bioprocess, the term 'lag phase' refers to:
The period where cells adapt before exponential growth
The delay in sensor response
The time taken to sterilize the reactor
The cooling period after fermentation
Explanation - During lag phase, cells prepare for rapid division, affecting process dynamics.
Correct answer is: The period where cells adapt before exponential growth
Q.134 Which of the following is NOT typically considered a 'critical quality attribute' (CQA) in bioprocessing?
Product purity
Cell viability
Reactor wall thickness
Glycosylation pattern
Explanation - CQA relate to product quality; reactor wall thickness is a design parameter.
Correct answer is: Reactor wall thickness
Q.135 A 'digital twin' of a bioreactor is primarily used for:
Replacing physical sensors
Virtual simulation, optimization, and predictive control
Reducing the reactor size
Increasing power consumption
Explanation - Digital twins mirror the physical system, enabling testing of control strategies without risk.
Correct answer is: Virtual simulation, optimization, and predictive control
Q.136 What does a 'low‑pass filter' do to a sensor signal?
Amplifies high‑frequency components
Attenuates high‑frequency noise while passing low‑frequency information
Converts analog to digital
Increases sensor range
Explanation - Low‑pass filtering smooths the signal, reducing the impact of noise on control.
Correct answer is: Attenuates high‑frequency noise while passing low‑frequency information
Q.137 Which control strategy combines the benefits of feedback and feed‑forward control?
On‑off control
Cascade control
Hybrid control
Dead‑band control
Explanation - Hybrid control uses feedback for correction and feed‑forward for anticipating disturbances.
Correct answer is: Hybrid control
Q.138 In a bioprocess, an 'impeller speed' of 300 rpm is increased to 500 rpm. The most immediate effect is:
Increase in pH
Increase in mixing and oxygen transfer
Decrease in temperature
Reduction in foam formation
Explanation - Higher impeller speed enhances shear and gas dispersion, raising kLa.
Correct answer is: Increase in mixing and oxygen transfer
Q.139 Which of the following best describes a 'dead‑time' in a control loop?
The time required for the controller to compute an output
The delay between a change in the manipulated variable and its effect on the measured variable
The time the actuator spends in standby mode
The sampling period of the sensor
Explanation - Dead‑time (transport delay) can degrade stability and must be compensated.
Correct answer is: The delay between a change in the manipulated variable and its effect on the measured variable
Q.140 A 'process analytical technology' (PAT) sensor network typically includes all EXCEPT:
Real‑time spectroscopic sensors
Manual off‑line sampling equipment
Data acquisition and analysis software
Control algorithms
Explanation - PAT aims for inline, real‑time data, reducing reliance on manual sampling.
Correct answer is: Manual off‑line sampling equipment
Q.141 When a bioprocess controller is set to a high integral gain, the most likely observed behavior is:
Slow response with no overshoot
Rapid elimination of steady‑state error but possible overshoot and oscillation
No change in control performance
Immediate actuator saturation without effect
Explanation - High integral gain can speed up error correction but may cause instability.
Correct answer is: Rapid elimination of steady‑state error but possible overshoot and oscillation
Q.142 Which of the following is a typical feature of a 'soft sensor' used in bioprocesses?
Physical contact with the broth
Use of mathematical models to estimate unmeasured variables
Requirement for frequent calibration
High power consumption
Explanation - Soft sensors rely on data and algorithms, not direct physical measurement.
Correct answer is: Use of mathematical models to estimate unmeasured variables