Q.1 Which sensor is most commonly used to monitor dissolved oxygen (DO) in a bioreactor?
pH electrode
DO probe
Temperature probe
Pressure transducer
Explanation - A dissolved oxygen probe measures the oxygen concentration directly in the culture medium, making it the standard sensor for DO monitoring.
Correct answer is: DO probe
Q.2 What does a pH electrode measure in a bioreactor?
Electrical conductivity
Acidity or alkalinity
Temperature
Oxygen levels
Explanation - A pH electrode generates a voltage related to the hydrogen ion activity, indicating the acidity or alkalinity of the solution.
Correct answer is: Acidity or alkalinity
Q.3 Which component is responsible for converting a process variable into an electrical signal?
Actuator
Controller
Sensor
Power supply
Explanation - A sensor converts a physical variable (like temperature or pressure) into an electrical signal that can be processed.
Correct answer is: Sensor
Q.4 In a bioreactor, the agitation speed is adjusted to maintain what key parameter?
Cell density
Dissolved oxygen
pH
Temperature
Explanation - Agitation improves mixing and oxygen transfer, directly affecting dissolved oxygen levels.
Correct answer is: Dissolved oxygen
Q.5 Which of the following is NOT typically an input to a PID controller in a bioprocess?
Process variable
Setpoint
Proportional gain
Thermal conductivity
Explanation - PID controllers use the process variable, setpoint, and controller parameters; thermal conductivity is not an input.
Correct answer is: Thermal conductivity
Q.6 What does the 'P' in PID stand for?
Pressure
Proportional
Phase
Power
Explanation - P represents the proportional term, which is proportional to the error between setpoint and process variable.
Correct answer is: Proportional
Q.7 A bioreactor's temperature is maintained by a heating jacket. Which sensor monitors this temperature?
Thermocouple
pH probe
DO probe
Pressure transducer
Explanation - Thermocouples measure temperature differences, suitable for monitoring the jacket temperature.
Correct answer is: Thermocouple
Q.8 Which actuator is used to control the flow rate of feed into a bioreactor?
Solenoid valve
Motor
Pump
Thermostat
Explanation - A pump regulates the liquid flow, allowing precise control of feed rates.
Correct answer is: Pump
Q.9 The term 'feedback control' refers to:
Adjusting inputs based on measured outputs
Using a feedforward strategy
Operating without sensors
Programming in advance
Explanation - Feedback control uses sensor measurements to adjust actuators and maintain desired conditions.
Correct answer is: Adjusting inputs based on measured outputs
Q.10 What is the purpose of a DO probe’s calibration?
To change its size
To ensure accurate readings
To sterilize the probe
To reduce cost
Explanation - Calibration aligns the probe’s output with known oxygen concentrations, improving measurement accuracy.
Correct answer is: To ensure accurate readings
Q.11 Which of the following is a typical output of a bioreactor controller?
pH value
Actuator command
Cell count
Temperature setpoint
Explanation - Controllers generate commands to actuators, such as valve positions or pump speeds, not direct process values.
Correct answer is: Actuator command
Q.12 Which term describes the time delay between a control action and its effect in a bioreactor?
Rise time
Settling time
Dead time
Overshoot
Explanation - Dead time refers to the lag between a control input and the observed change in the process.
Correct answer is: Dead time
Q.13 In a PID controller, the integral term is primarily used to:
Reduce overshoot
Eliminate steady-state error
Increase response speed
Add noise filtering
Explanation - The integral term accumulates error over time, driving the steady-state error to zero.
Correct answer is: Eliminate steady-state error
Q.14 Which sensor would you use to monitor pressure in a bioreactor's headspace?
pH electrode
Pressure transducer
Temperature probe
Dissolved oxygen probe
Explanation - Pressure transducers convert pressure differences into voltage or current signals.
Correct answer is: Pressure transducer
Q.15 What does SCADA stand for in process control?
Supervisory Control and Data Acquisition
Standard Control and Data Automation
Signal Control and Data Analysis
Sensor Calibration and Data Assessment
Explanation - SCADA systems monitor and control industrial processes while collecting data for analysis.
Correct answer is: Supervisory Control and Data Acquisition
Q.16 A bioprocess HMI typically displays:
Process variables and alarms
Only raw sensor data
Actuator positions only
Power consumption only
Explanation - Human-Machine Interfaces (HMI) show real-time variables, trends, and alarms for operator interaction.
Correct answer is: Process variables and alarms
Q.17 Which of these is a common method for DO sensor calibration?
Zeroing at atmospheric oxygen
Using a nitrogen purge
Mixing with hydrogen peroxide
Heating the sensor to 100°C
Explanation - A typical calibration uses air-saturated water (approx 8 mg/L at 25°C) as a zero point.
Correct answer is: Zeroing at atmospheric oxygen
Q.18 What is the purpose of a feedforward controller in a bioreactor?
To correct errors after they occur
To anticipate disturbances and compensate in advance
To replace feedback control entirely
To reduce sensor noise
Explanation - Feedforward control uses known disturbances to preemptively adjust actuators before the error manifests.
Correct answer is: To anticipate disturbances and compensate in advance
Q.19 Which of the following is NOT typically part of a bioreactor instrumentation set?
pH sensor
DO sensor
Magnetic stirrer
Flowmeter
Explanation - A magnetic stirrer is an agitation device, not an instrumentation sensor.
Correct answer is: Magnetic stirrer
Q.20 In a bioprocess, the term 'oxygen transfer rate' (OTR) refers to:
The maximum oxygen concentration in the medium
The rate at which oxygen is transferred from gas phase to liquid
The amount of oxygen dissolved in the cell mass
The rate at which cells consume oxygen
Explanation - OTR quantifies the mass transfer rate of oxygen into the liquid phase of the bioreactor.
Correct answer is: The rate at which oxygen is transferred from gas phase to liquid
Q.21 Which signal conditioning device is commonly used with a temperature probe in a bioreactor?
Amplifier
Rectifier
Filter
Inverter
Explanation - Temperature probes often produce low-level voltage or current signals that require amplification before digitization.
Correct answer is: Amplifier
Q.22 A bioreactor's pressure setpoint is increased. What is the most likely effect on the dissolved oxygen concentration?
Increased DO
Decreased DO
No change
Immediate cell death
Explanation - Higher pressure increases gas solubility, thus raising dissolved oxygen levels.
Correct answer is: Increased DO
Q.23 Which component provides the power to all instrumentation in a bioreactor?
Generator
Transformer
Power supply
Battery
Explanation - The power supply converts mains voltage to the required levels for sensors, controllers, and actuators.
Correct answer is: Power supply
Q.24 Which of the following is a typical alarm condition for a DO probe?
Temperature too high
pH too low
Signal loss
Valve stuck
Explanation - An alarm is triggered if the DO probe fails to provide a valid signal, indicating potential failure.
Correct answer is: Signal loss
Q.25 In a PID controller, increasing the derivative gain typically:
Increases overshoot
Reduces oscillations
Decreases response time
Has no effect
Explanation - The derivative term predicts future error, dampening oscillatory behavior.
Correct answer is: Reduces oscillations
Q.26 The 'settling time' of a bioreactor process is defined as:
Time for the process to reach 90% of the final value
Time to reach the setpoint from zero
Time to stabilize within ±5% of the final value
Time until the first measurement
Explanation - Settling time measures the period until the process variable remains within a specified band around its final value.
Correct answer is: Time to stabilize within ±5% of the final value
Q.27 Which of these is a direct measurement of cell density in a bioreactor?
Optical density (OD)
Dissolved oxygen
Temperature
pH
Explanation - OD measures light scattering by cells, correlating with cell concentration.
Correct answer is: Optical density (OD)
Q.28 What is the primary function of a level sensor in a bioreactor?
Monitor temperature
Measure liquid height
Control gas flow
Detect pH changes
Explanation - Level sensors keep the liquid volume within desired limits to avoid overfilling or draining.
Correct answer is: Measure liquid height
Q.29 A typical bioprocess PLC uses what communication protocol for sensor inputs?
Ethernet/IP
Modbus RTU
CAN bus
All of the above
Explanation - PLCs support various industrial protocols like Ethernet/IP, Modbus, and CAN for interfacing devices.
Correct answer is: All of the above
Q.30 Which of the following is a major safety requirement for bioreactor instrumentation?
Use of non-conductive materials
Redundant sensors for critical variables
High voltage operation
Large physical size
Explanation - Redundancy ensures reliable operation in case one sensor fails, critical for safety.
Correct answer is: Redundant sensors for critical variables
Q.31 The 'zero' calibration of a pH sensor is typically performed using:
Pure water
pH 7 buffer
pH 4 buffer
pH 9 buffer
Explanation - pH 7 is the neutral point used to set the zero reading on a pH electrode.
Correct answer is: pH 7 buffer
Q.32 A bioreactor's agitation speed is increased to improve which of the following?
Mixing homogeneity
Cell growth rate
Oxygen transfer rate
All of the above
Explanation - Higher agitation enhances mixing, increases DO transfer, and can boost cell productivity.
Correct answer is: All of the above
Q.33 Which type of control strategy is used to maintain a constant temperature in a bioreactor?
Feedforward
Feedback
Open-loop
Closed-loop
Explanation - Feedback control adjusts heating/cooling based on temperature sensor readings to keep the setpoint constant.
Correct answer is: Feedback
Q.34 A bioreactor controller that adjusts the oxygen supply based on DO sensor feedback is an example of:
Proportional control only
PID control
Feedforward control
Open-loop control
Explanation - Most DO controllers use PID loops to maintain DO setpoints by adjusting aeration and agitation.
Correct answer is: PID control
Q.35 The term 'process variable' (PV) refers to:
Desired setpoint
Measured process condition
Control algorithm
Actuator output
Explanation - PV is the actual measured value of a process variable, e.g., temperature or pH.
Correct answer is: Measured process condition
Q.36 Which of the following is an example of a non-invasive bioreactor sensor?
Dissolved oxygen probe
pH electrode
Optical density measurement
Pressure transducer
Explanation - OD sensors use light transmission through the culture, not inserted into the medium.
Correct answer is: Optical density measurement
Q.37 What does 'setpoint' refer to in process control?
The desired target value
The measured process value
The error value
The controller output
Explanation - The setpoint is the value the controller strives to maintain.
Correct answer is: The desired target value
Q.38 A bioreactor controller typically uses which type of output signal to drive an actuator?
Analog voltage (0-10 V)
Digital pulse
Current (4-20 mA)
All of the above
Explanation - Controllers can output voltage, current, or digital signals depending on the actuator.
Correct answer is: All of the above
Q.39 Which safety feature protects a bioreactor from over-pressurization?
Pressure relief valve
Temperature probe
pH sensor
Flowmeter
Explanation - A relief valve opens when pressure exceeds a set threshold, preventing damage.
Correct answer is: Pressure relief valve
Q.40 Which of the following sensors is typically used to monitor the pH of a bioprocess?
pH electrode
Oxygen probe
Thermocouple
Pressure transducer
Explanation - pH electrodes measure hydrogen ion activity, directly reflecting acidity/alkalinity.
Correct answer is: pH electrode
Q.41 In a bioreactor, what does a 'dead time' of 5 minutes mean?
The controller takes 5 minutes to start
The sensor signals are delayed by 5 minutes
The process variable takes 5 minutes to respond after a control action
The reactor needs 5 minutes before operation
Explanation - Dead time is the lag between a control input and the observed effect on the process.
Correct answer is: The process variable takes 5 minutes to respond after a control action
Q.42 Which of these is a typical advantage of using a 4-20 mA current loop for sensor signals?
High noise immunity
Easy to amplify
Low cost
Large dynamic range
Explanation - Current loops are immune to voltage drops and electrical interference, ideal for long cables.
Correct answer is: High noise immunity
Q.43 The main goal of 'process monitoring' in bioreactors is to:
Predict future market demand
Track variables in real time for control decisions
Measure the weight of the bioreactor
Calibrate sensors monthly
Explanation - Monitoring provides data needed for timely control actions and quality assurance.
Correct answer is: Track variables in real time for control decisions
Q.44 What does 'sampling' in a bioreactor context refer to?
Taking a small volume of culture for analysis
Drawing a sensor probe
Measuring temperature
Adjusting aeration rate
Explanation - Sampling collects material from the reactor for laboratory tests, e.g., cell count or metabolite analysis.
Correct answer is: Taking a small volume of culture for analysis
Q.45 Which control loop would be most appropriate for maintaining constant dissolved oxygen while accounting for changes in biomass concentration?
Open-loop
PID with feedforward on cell density
Manual control
Deadband control
Explanation - A feedforward term using biomass helps predict DO changes caused by increased oxygen demand.
Correct answer is: PID with feedforward on cell density
Q.46 What does an 'alarm threshold' for DO usually indicate?
A permissible range for DO
A target DO setpoint
A maximum allowable DO value
A minimum allowable DO value for operation
Explanation - Alarms trigger if DO falls below a critical threshold, signaling possible process failure.
Correct answer is: A minimum allowable DO value for operation
Q.47 The term 'setpoint drift' refers to:
A change in the desired target over time
A sensor output moving away from zero
A controller output exceeding limits
An actuator failing to respond
Explanation - Setpoint drift occurs when the target value changes, intentionally or due to malfunction.
Correct answer is: A change in the desired target over time
Q.48 Which of the following best describes 'PID tuning'?
Adjusting sensor calibration
Choosing the correct setpoint
Adjusting proportional, integral, and derivative gains
Changing the process variable
Explanation - Tuning modifies PID parameters to achieve desired transient and steady‑state performance.
Correct answer is: Adjusting proportional, integral, and derivative gains
Q.49 A typical bioreactor DO probe is made from:
Platinum wire
Graphite rod
Silver chloride electrode
All of the above
Explanation - DO probes often contain platinum or graphite for oxygen sensing and a silver chloride reference.
Correct answer is: All of the above
Q.50 Which type of sensor is used to detect the presence of a gas phase in a bioreactor?
Pressure transducer
Flowmeter
Gas analyzer
Temperature probe
Explanation - Gas analyzers measure concentrations of gases in the headspace, such as CO₂ or O₂.
Correct answer is: Gas analyzer
Q.51 In a bioprocess, what is a 'steady state' condition?
Process variable is at zero
Process variables remain constant over time
The reactor is filling with medium
The cells are dividing rapidly
Explanation - Steady state means all variables are stable, allowing accurate measurement and control.
Correct answer is: Process variables remain constant over time
Q.52 Which of the following is a typical function of a process historian in a bioreactor system?
Collecting and storing time‑series data
Controlling actuators
Calibrating sensors
Operating the bioreactor
Explanation - A historian records data for analysis, reporting, and traceability.
Correct answer is: Collecting and storing time‑series data
Q.53 What type of controller is commonly used to maintain a constant pH in a bioreactor?
On‑off controller
PID controller
Feedforward controller
Manual controller
Explanation - PID provides smooth adjustment of acid/base addition to keep pH at its setpoint.
Correct answer is: PID controller
Q.54 A bioreactor's agitation speed is often controlled by:
A DC motor with speed controller
A pneumatic cylinder
A stepper motor
A hydraulic pump
Explanation - Agitators typically use DC motors whose speed is regulated by a controller.
Correct answer is: A DC motor with speed controller
Q.55 Which component provides a reference voltage or current for sensor signals?
Signal conditioner
Power supply
Reference resistor
Signal generator
Explanation - Signal conditioners generate stable reference signals and filter noise before digitization.
Correct answer is: Signal conditioner
Q.56 The main purpose of a 'buffer' in bioprocess instrumentation is to:
Store excess liquid
Reduce signal noise
Maintain constant pH
Act as a sensor
Explanation - Signal buffers stabilize voltage or current signals, reducing interference.
Correct answer is: Reduce signal noise
Q.57 Which of the following is a common method for calibrating a temperature probe?
Ice bath for 0°C
Boiling water for 100°C
Dry air at 25°C
All of the above
Explanation - Calibrating at multiple known points ensures accurate temperature readings.
Correct answer is: All of the above
Q.58 A bioreactor controller that adjusts the feed rate based on the measured cell density is an example of:
Proportional control
Integral control
Feedforward control
Deadband control
Explanation - Feedforward uses measured biomass to predict future nutrient demand and adjust feeding.
Correct answer is: Feedforward control
Q.59 The term 'linearity' in instrumentation refers to:
Sensor accuracy
Direct proportionality between input and output
Speed of response
Signal bandwidth
Explanation - A linear sensor produces an output directly proportional to the measured variable.
Correct answer is: Direct proportionality between input and output
Q.60 Which of these is NOT a typical variable in bioreactor control loops?
Temperature
pH
Cell density
Wind speed
Explanation - Wind speed is unrelated to bioprocess control variables.
Correct answer is: Wind speed
Q.61 The 'feedback' in a control system is best described as:
The input to the controller
The error signal
The difference between setpoint and PV
The controller output
Explanation - Feedback is the measured error used by the controller to compute the output.
Correct answer is: The difference between setpoint and PV
Q.62 What does the 'integral' part of a PID controller do?
Eliminate steady-state error
Reduce overshoot
Predict future error
Provide an initial response
Explanation - The integral term accumulates the error over time, driving it toward zero.
Correct answer is: Eliminate steady-state error
Q.63 A bioreactor's 'oxygen transfer rate' is often expressed in units of:
mg/L·h
L/min
Pa·s
Watt
Explanation - OTR quantifies oxygen mass transfer per liter per hour.
Correct answer is: mg/L·h
Q.64 Which of these is a common safety instrumentation for a bioreactor?
Pressure relief valve
Thermostat
Light bulb
Handhold
Explanation - Pressure relief valves protect against over‑pressurization and potential equipment damage.
Correct answer is: Pressure relief valve
Q.65 A 'deadband' in control theory is defined as:
The maximum error tolerated before action
A region around setpoint where no control action is taken
The time delay in the system
The speed of the actuator
Explanation - Deadband helps reduce controller chatter by ignoring minor deviations.
Correct answer is: A region around setpoint where no control action is taken
Q.66 What is the purpose of a 'process historian' in bioprocess control?
To record and archive process data
To calibrate sensors
To control temperature
To clean the bioreactor
Explanation - A historian stores historical data for analysis, compliance, and troubleshooting.
Correct answer is: To record and archive process data
Q.67 Which of these is a typical input signal type used in PLCs for bioreactors?
4-20 mA
0-10 V
Digital pulse
All of the above
Explanation - PLCs accept various analog and digital signals from instruments.
Correct answer is: All of the above
Q.68 Which of these control strategies best compensates for known disturbances in a bioprocess?
Open‑loop control
Feedforward control
Deadband control
Manual control
Explanation - Feedforward anticipates disturbances and adjusts setpoints proactively.
Correct answer is: Feedforward control
Q.69 A sensor that measures the concentration of a specific metabolite in a bioreactor is called a:
Probe
Analytical sensor
Calibration sensor
Temperature sensor
Explanation - Analytical sensors provide chemical concentration data, such as glucose or lactate.
Correct answer is: Analytical sensor
Q.70 In the context of bioreactors, what does the 'setpoint drift' typically indicate?
A malfunctioning sensor
An intentional change in the desired process condition
A sensor becoming noisy
The process variable overshooting
Explanation - Setpoint drift can occur due to process adjustments or controller misconfiguration.
Correct answer is: An intentional change in the desired process condition
Q.71 The primary function of a level sensor in a bioreactor is to:
Measure the volume of liquid
Control the temperature
Monitor the oxygen level
Adjust the pH
Explanation - Level sensors keep the liquid height within safe limits to avoid over‑filling or under‑filling.
Correct answer is: Measure the volume of liquid
Q.72 Which of the following best describes 'integral action' in a PID controller?
It amplifies the error instantly
It sums error over time to eliminate steady‑state error
It differentiates the error
It sets the error to zero immediately
Explanation - Integral action accumulates the error, driving the controller output to eliminate residual error.
Correct answer is: It sums error over time to eliminate steady‑state error
Q.73 What is the most common type of power supply used in bioreactor instrumentation?
AC mains
DC supply
Battery backup
Solar panel
Explanation - Instrumentation typically requires stable DC power for sensors, controllers, and actuators.
Correct answer is: DC supply
Q.74 Which of these is NOT a typical parameter monitored in a bioreactor?
Temperature
pH
Humidity
Oxygen concentration
Explanation - Humidity is irrelevant to liquid culture conditions.
Correct answer is: Humidity
Q.75 Which of the following is a typical method for measuring dissolved oxygen in a bioreactor?
Clark electrode
Thermocouple
pH electrode
Optical sensor
Explanation - Clark type electrodes are widely used for DO measurement.
Correct answer is: Clark electrode
Q.76 The purpose of a 'reference electrode' in a DO probe is to:
Maintain the probe’s temperature
Provide a stable electrical reference
Act as a backup sensor
Measure pH
Explanation - The reference electrode allows the probe to measure oxygen concentration accurately.
Correct answer is: Provide a stable electrical reference
Q.77 Which component of a bioreactor provides mechanical agitation?
Impeller
Stir bar
Aeration sparger
Temperature probe
Explanation - Impellers rotate to mix the culture, improving mass transfer.
Correct answer is: Impeller
Q.78 A 'process variable' in bioprocess control is:
The measured value of a process condition
The target value set by the operator
The difference between setpoint and measurement
The controller output
Explanation - PV is what the controller reads from sensors to compare with the setpoint.
Correct answer is: The measured value of a process condition
Q.79 Which of these is a common application of SCADA in bioprocesses?
Monitoring and recording process variables
Manually turning valves
Calibrating sensors
Designing bioreactors
Explanation - SCADA collects data and provides supervisory control over the entire plant.
Correct answer is: Monitoring and recording process variables
Q.80 Which of the following is an example of a 'closed‑loop' control system in bioreactors?
An open‑air fermenter
A controller maintaining temperature via a heater
A manual stirrer
A fixed aeration rate
Explanation - Closed‑loop uses sensor feedback to adjust actuators automatically.
Correct answer is: A controller maintaining temperature via a heater
Q.81 The 'deadband' in a controller is used to:
Increase controller sensitivity
Reduce noise and chatter
Set a maximum output
Provide an alarm threshold
Explanation - Deadband ignores small errors to prevent unnecessary actuator adjustments.
Correct answer is: Reduce noise and chatter
Q.82 Which of these is a typical sensor used to measure the pH of a bioreactor?
pH electrode
Temperature probe
DO probe
Pressure sensor
Explanation - A pH electrode is the standard device for measuring acidity or alkalinity.
Correct answer is: pH electrode
Q.83 The term 'setpoint' refers to:
Desired process condition
Actual measured condition
Controller output
Error between PV and SP
Explanation - The setpoint is the target value the controller seeks to maintain.
Correct answer is: Desired process condition
Q.84 A typical bioreactor pressure sensor is usually:
A pressure transducer
A temperature probe
A DO probe
A pH electrode
Explanation - Pressure transducers convert pressure differences to electrical signals.
Correct answer is: A pressure transducer
Q.85 Which of the following is the best way to reduce sensor drift in a bioreactor?
Regular calibration
Increase setpoint
Add more cells
Change the agitation speed
Explanation - Routine calibration keeps sensor output accurate over time.
Correct answer is: Regular calibration
Q.86 The main advantage of a 4‑20 mA sensor output is:
Easy to amplify
Low noise immunity over long cables
High voltage operation
Large bandwidth
Explanation - Current loops are robust against voltage drops and electrical noise.
Correct answer is: Low noise immunity over long cables
Q.87 Which of the following best describes a 'process variable'?
The target setpoint
The measured value from a sensor
The controller output
The error signal
Explanation - Process variable is the actual measurement of a process condition.
Correct answer is: The measured value from a sensor
Q.88 Which of these is a key function of a bioreactor controller?
Monitor process variables
Adjust actuators
Record data
All of the above
Explanation - Controllers perform measurement, control, and data logging tasks.
Correct answer is: All of the above
Q.89 A 'deadband' is a:
Range of acceptable error where no action is taken
Maximum sensor value
Time delay in the system
Type of controller
Explanation - Deadband prevents frequent small adjustments when the variable is close to the setpoint.
Correct answer is: Range of acceptable error where no action is taken
Q.90 Which of these is used to measure cell density in a bioreactor?
Optical density (OD)
pH probe
DO probe
Temperature probe
Explanation - OD measures light scattering by cells, correlating with cell concentration.
Correct answer is: Optical density (OD)
Q.91 What is the main purpose of a level sensor in a bioreactor?
Measure liquid height
Monitor temperature
Control pH
Detect dissolved oxygen
Explanation - Level sensors keep the liquid volume within safe limits.
Correct answer is: Measure liquid height
Q.92 Which of the following best describes 'PID tuning'?
Adjusting sensor calibration
Choosing the correct setpoint
Adjusting proportional, integral, and derivative gains
Changing the process variable
Explanation - Tuning modifies PID parameters to achieve desired performance.
Correct answer is: Adjusting proportional, integral, and derivative gains
Q.93 A bioreactor's temperature is typically controlled by:
A heater in the jacket
A cooling coil
Both A and B
Neither
Explanation - Temperature is maintained using heating and cooling elements as needed.
Correct answer is: Both A and B
Q.94 In a PID controller, the 'integral' term primarily helps to:
Reduce overshoot
Eliminate steady‑state error
Increase response speed
Filter noise
Explanation - Integral action accumulates error over time to drive it toward zero.
Correct answer is: Eliminate steady‑state error
Q.95 A bioreactor's oxygen transfer rate (OTR) is:
The rate of oxygen consumption by cells
The rate of oxygen transfer from gas to liquid
The amount of dissolved oxygen
The rate of agitation
Explanation - OTR measures how quickly oxygen moves into the liquid phase.
Correct answer is: The rate of oxygen transfer from gas to liquid
Q.96 Which of the following is a key parameter monitored in a bioreactor?
Temperature
pH
Cell density
All of the above
Explanation - Temperature, pH, and cell density are essential for controlling the bioprocess.
Correct answer is: All of the above
Q.97 Which type of controller is typically used for maintaining constant dissolved oxygen in a bioreactor?
On‑off
PID
Feedforward
Manual
Explanation - PID controllers provide smooth control over DO by adjusting aeration and agitation.
Correct answer is: PID
Q.98 What is a common safety device used to protect a bioreactor from over‑pressurization?
Pressure relief valve
Temperature probe
pH sensor
Flowmeter
Explanation - The valve opens automatically when pressure exceeds a preset limit.
Correct answer is: Pressure relief valve
Q.99 What does a 'controller output' (CO) represent?
Setpoint value
Measured process variable
Actuator command
Error signal
Explanation - The controller output is the signal sent to an actuator to influence the process.
Correct answer is: Actuator command
Q.100 The 'integral' component of a PID controller helps to:
Eliminate steady‑state error
Increase overshoot
Reduce response time
Add noise
Explanation - Integral action accumulates error over time to drive steady‑state error to zero.
Correct answer is: Eliminate steady‑state error
Q.101 Which of these is NOT a typical sensor in a bioreactor?
Temperature probe
pH electrode
Oxygen probe
Wind speed sensor
Explanation - Wind speed is irrelevant to bioreactor operation.
Correct answer is: Wind speed sensor
Q.102 In bioreactor instrumentation, a 'reference electrode' is used to:
Provide a stable electrical reference
Measure temperature
Detect oxygen
Measure pH
Explanation - The reference electrode supplies a constant potential for accurate voltage measurement.
Correct answer is: Provide a stable electrical reference
Q.103 What is the main purpose of a 'process historian' in a bioreactor?
Control the agitation speed
Record process data over time
Calibrate sensors
Maintain temperature
Explanation - A historian collects and stores data for analysis, compliance, and troubleshooting.
Correct answer is: Record process data over time
Q.104 Which of these best describes a 'feedback' control loop?
Uses a known disturbance to adjust control
Uses sensor measurements to adjust actuators
Operates without sensors
Adjusts setpoint automatically
Explanation - Feedback uses real‑time sensor data to keep the process at its setpoint.
Correct answer is: Uses sensor measurements to adjust actuators
Q.105 Which of the following is a typical method for calibrating a DO probe?
Zeroing in air-saturated water
Zeroing in nitrogen-saturated water
Zeroing in pure water
Zeroing in pure oxygen
Explanation - Air-saturated water (~8 mg/L at 25°C) is used as the zero reference for DO probes.
Correct answer is: Zeroing in air-saturated water
Q.106 What is the purpose of a 'deadband' in a control system?
Increase controller sensitivity
Reduce noise and chatter
Provide a maximum output
Set an alarm threshold
Explanation - Deadband eliminates minor fluctuations in the process variable from triggering the controller.
Correct answer is: Reduce noise and chatter
Q.107 In a bioreactor, which sensor would you use to monitor the gas composition in the headspace?
Temperature probe
pH electrode
Gas analyzer
Pressure transducer
Explanation - Gas analyzers measure concentrations of gases such as CO₂ and O₂.
Correct answer is: Gas analyzer
Q.108 What is the main function of a temperature probe in a bioreactor?
Measure temperature
Measure pressure
Measure oxygen
Measure pH
Explanation - Temperature probes provide real‑time temperature data for control.
Correct answer is: Measure temperature
Q.109 Which of the following best describes a 'feedforward' control strategy?
Acting after the error occurs
Acting before the error occurs by compensating for known disturbances
Ignoring all disturbances
Using open-loop control
Explanation - Feedforward anticipates changes and adjusts the control action preemptively.
Correct answer is: Acting before the error occurs by compensating for known disturbances
Q.110 What is the typical output signal of a bioreactor DO probe?
0–10 V
4–20 mA
Digital pulse
All of the above
Explanation - DO probes can be configured to output various analog or digital signals.
Correct answer is: All of the above
Q.111 Which component in a bioreactor is primarily responsible for aeration?
Impeller
Sparger
Pump
Stir bar
Explanation - A sparger introduces gas bubbles into the medium, providing oxygen.
Correct answer is: Sparger
Q.112 Which of the following is a typical measurement for monitoring cell growth?
pH
Oxygen concentration
Optical density (OD)
Temperature
Explanation - OD correlates with cell concentration through light scattering.
Correct answer is: Optical density (OD)
Q.113 Which of these is a typical parameter measured by a bioreactor's level sensor?
Liquid height
Temperature
Oxygen concentration
pH
Explanation - Level sensors detect the liquid level to prevent overflow or air exposure.
Correct answer is: Liquid height
Q.114 What is the main function of an HMI in a bioprocess?
Control the agitation speed
Display process variables and alarms to operators
Calibrate sensors
Maintain temperature
Explanation - HMI provides a user interface for monitoring and interacting with the control system.
Correct answer is: Display process variables and alarms to operators
Q.115 Which of the following is NOT a typical function of a controller in a bioreactor?
Receive sensor inputs
Calculate control output
Actuate valves and pumps
Log historical data
Explanation - Logging is usually handled by a historian or separate data acquisition system.
Correct answer is: Log historical data
Q.116 Which of these is a typical sensor type for measuring dissolved oxygen?
Clark electrode
Thermocouple
pH electrode
Pressure transducer
Explanation - Clark-type electrodes are widely used for DO measurement.
Correct answer is: Clark electrode
Q.117 The term 'dead time' refers to:
The time delay between sensor input and controller output
The time delay between controller output and process variable response
The time a sensor takes to calibrate
The time a bioreactor needs to fill
Explanation - Dead time is the lag between a control action and the observable process effect.
Correct answer is: The time delay between controller output and process variable response
Q.118 Which of the following is a key benefit of using a 4‑20 mA loop for sensor signals?
High voltage operation
Low noise immunity over long distances
Large bandwidth
Simple voltage amplification
Explanation - Current loops are resistant to voltage drops and electromagnetic interference.
Correct answer is: Low noise immunity over long distances
Q.119 Which of the following is a typical parameter monitored in a bioreactor process?
Temperature
pH
Oxygen concentration
All of the above
Explanation - Temperature, pH, and oxygen are essential for controlling the bioprocess environment.
Correct answer is: All of the above
Q.120 What does the 'integral' action in a PID controller do?
Eliminate steady‑state error
Increase overshoot
Reduce response time
Add noise to the signal
Explanation - Integral accumulates error over time, driving it to zero.
Correct answer is: Eliminate steady‑state error
Q.121 A bioreactor's pressure sensor is typically a _________.
Pressure transducer
Temperature probe
pH electrode
Oxygen probe
Explanation - Pressure transducers convert pressure differences into electrical signals.
Correct answer is: Pressure transducer
Q.122 Which of the following is NOT typically part of a bioreactor's instrumentation set?
pH sensor
Oxygen sensor
Wind speed sensor
Temperature sensor
Explanation - Wind speed has no relevance to the bioprocess.
Correct answer is: Wind speed sensor
Q.123 A bioreactor controller that adjusts aeration based on DO readings is an example of a _________.
Feedforward controller
PID controller
Open‑loop controller
Manual controller
Explanation - PID controllers use sensor feedback to modulate aeration and agitation.
Correct answer is: PID controller
Q.124 Which of the following best describes the 'process variable' (PV) in control theory?
The measured value of a process condition
The target value set by the operator
The controller's output signal
The error between setpoint and PV
Explanation - PV is the actual measurement obtained from sensors.
Correct answer is: The measured value of a process condition
Q.125 What is the purpose of a bioreactor's level sensor?
To maintain liquid volume
To monitor temperature
To measure oxygen
To control pH
Explanation - Level sensors ensure the liquid stays within safe limits.
Correct answer is: To maintain liquid volume
Q.126 Which sensor type is commonly used to measure dissolved oxygen in a bioreactor?
Temperature probe
pH electrode
Clark electrode
Pressure transducer
Explanation - Clark electrodes are the standard for DO measurement.
Correct answer is: Clark electrode
Q.127 Which of the following is an example of a control variable in a bioprocess?
Temperature
Humidity
Wind speed
Color of the medium
Explanation - Temperature, pH, DO are typical control variables.
Correct answer is: Temperature
Q.128 A 'deadband' in a control system is best described as:
The maximum allowable error before action
A range where the controller does not act
The time delay in the system
The type of sensor used
Explanation - Deadband prevents the controller from reacting to small deviations.
Correct answer is: A range where the controller does not act
Q.129 Which of these is a typical function of a process historian?
Record time‑series data
Control the agitator
Calibrate sensors
Maintain temperature
Explanation - A historian logs data for analysis and regulatory compliance.
Correct answer is: Record time‑series data
Q.130 In a bioreactor, which sensor would you use to monitor the cell density?
pH electrode
Temperature probe
Optical density sensor
Pressure transducer
Explanation - OD sensors provide a quick estimate of cell concentration.
Correct answer is: Optical density sensor
Q.131 Which of the following is an advantage of using a 4‑20 mA loop for sensor signals?
High noise immunity over long cables
Easy to amplify
High voltage operation
Large bandwidth
Explanation - Current loops are robust against voltage drops and EMI.
Correct answer is: High noise immunity over long cables
Q.132 What does 'PID' stand for in process control?
Proportional, Integral, Derivative
Pressure, I, D
Power, Input, Demand
Position, I, D
Explanation - PID controllers combine these three terms for effective control.
Correct answer is: Proportional, Integral, Derivative
Q.133 Which component is responsible for converting a sensor's electrical signal to an actuator command?
Sensor
Actuator
Controller
Power supply
Explanation - The controller processes the sensor signal and generates an output for the actuator.
Correct answer is: Controller
Q.134 Which of the following is NOT a typical input to a bioreactor controller?
Process variable
Setpoint
Proportional gain
Ambient humidity
Explanation - Ambient humidity is not a direct process variable in a typical bioreactor.
Correct answer is: Ambient humidity
Q.135 What type of signal does a standard pH electrode produce?
Voltage
Current
Digital pulse
All of the above
Explanation - pH electrodes generate a voltage proportional to hydrogen ion activity.
Correct answer is: Voltage
Q.136 A bioreactor's agitation speed is controlled by:
A DC motor with speed control
A pneumatic cylinder
A stepper motor
A hydraulic pump
Explanation - Agitators use DC motors whose speed is regulated by a controller.
Correct answer is: A DC motor with speed control
Q.137 Which of the following is an example of a 'deadband' in bioprocess control?
Ignoring small variations around the setpoint
Increasing controller gain
Using open‑loop control
Adjusting the setpoint manually
Explanation - Deadband prevents controller action for minor deviations.
Correct answer is: Ignoring small variations around the setpoint
Q.138 What is the main purpose of a temperature probe in a bioreactor?
Measure temperature
Measure pressure
Measure dissolved oxygen
Measure pH
Explanation - Temperature probes provide the data needed for temperature control.
Correct answer is: Measure temperature
Q.139 Which of the following best describes a 'feedback' controller?
Acts before a disturbance occurs
Responds after the error is observed
Does not use any sensors
Uses a pre-set schedule
Explanation - Feedback control reacts to deviations detected by sensors.
Correct answer is: Responds after the error is observed
Q.140 Which of the following is typically measured by a level sensor in a bioreactor?
Liquid height
Temperature
pH
Oxygen concentration
Explanation - Level sensors monitor the volume of liquid to prevent overflow or under‑fill.
Correct answer is: Liquid height
Q.141 In a bioreactor, what is the main advantage of a 4‑20 mA signal output from sensors?
Low noise immunity over long cables
Simple voltage amplification
High voltage operation
Large bandwidth
Explanation - Current loops are robust against voltage drops and electromagnetic interference.
Correct answer is: Low noise immunity over long cables
Q.142 Which component is responsible for converting the controller's output into a physical action in a bioreactor?
Sensor
Actuator
Controller
Power supply
Explanation - The actuator implements the control signal by changing a physical variable.
Correct answer is: Actuator
Q.143 What is the purpose of a bioreactor's pressure relief valve?
To prevent over‑pressurization
To maintain temperature
To calibrate sensors
To stir the culture
Explanation - The valve releases pressure when a set threshold is exceeded.
Correct answer is: To prevent over‑pressurization
Q.144 Which of the following is a typical input to a bioreactor controller?
Process variable
Setpoint
Proportional gain
All of the above
Explanation - Controllers use the measured process variable, setpoint, and internal parameters.
Correct answer is: All of the above
Q.145 What is the typical output signal from a temperature probe in a bioreactor?
Voltage
Current
Digital pulse
All of the above
Explanation - Temperature probes often output a voltage proportional to temperature.
Correct answer is: Voltage
Q.146 Which of the following best describes a 'deadband' in a control system?
A range where the controller does not act
The maximum allowed error before action
The time delay in the system
The type of sensor used
Explanation - Deadband helps avoid unnecessary actuation for small deviations.
Correct answer is: A range where the controller does not act
Q.147 What is the primary function of a bioreactor's pH sensor?
Measure temperature
Measure acidity or alkalinity
Measure dissolved oxygen
Measure pressure
Explanation - The pH sensor provides data for maintaining the desired pH range.
Correct answer is: Measure acidity or alkalinity
Q.148 Which of the following is typically used to monitor the oxygen level in a bioreactor?
Oxygen probe
Temperature probe
pH probe
Pressure transducer
Explanation - Oxygen probes (e.g., Clark electrode) measure dissolved oxygen concentrations.
Correct answer is: Oxygen probe
Q.149 Which of the following best describes a PID controller's 'proportional' term?
It reduces the steady‑state error
It responds to the current error magnitude
It differentiates the error
It introduces a time delay
Explanation - The proportional term is directly proportional to the current error.
Correct answer is: It responds to the current error magnitude
Q.150 Which of the following is a typical parameter monitored by a bioreactor's level sensor?
Liquid height
Temperature
Pressure
Cell density
Explanation - Level sensors ensure the liquid stays within safe limits.
Correct answer is: Liquid height
Q.151 The main purpose of a pressure transducer in a bioreactor is to:
Measure liquid height
Measure pressure
Measure dissolved oxygen
Measure pH
Explanation - Pressure transducers convert pressure differences into electrical signals.
Correct answer is: Measure pressure
Q.152 Which of the following best describes the 'integral' action in a PID controller?
Reduces steady‑state error
Increases overshoot
Accelerates response
Adds noise
Explanation - The integral term accumulates error over time to eliminate steady‑state error.
Correct answer is: Reduces steady‑state error
Q.153 A bioreactor's agitation system typically consists of a(n):
Impeller
Sparger
Pump
Stir bar
Explanation - An impeller rotates to mix the culture, improving mass transfer.
Correct answer is: Impeller
Q.154 Which of the following is NOT a typical input to a bioreactor controller?
Setpoint
Process variable
Proportional gain
Ambient humidity
Explanation - Ambient humidity is not directly relevant to most bioreactor control loops.
Correct answer is: Ambient humidity
Q.155 Which of the following best describes the 'deadband' concept in control systems?
A range where the controller does not act
The maximum error before action
The delay between input and output
The type of sensor used
Explanation - Deadband avoids unnecessary adjustments for minor deviations.
Correct answer is: A range where the controller does not act
Q.156 What is the primary function of an HMI in a bioprocess?
Display process variables and alarms
Control the agitation speed
Calibrate sensors
Maintain temperature
Explanation - The HMI provides a user interface for monitoring and interacting with the control system.
Correct answer is: Display process variables and alarms
Q.157 Which of the following is a typical sensor used in bioreactor instrumentation?
pH electrode
Temperature probe
Oxygen probe
All of the above
Explanation - All listed sensors are standard in bioreactor instrumentation.
Correct answer is: All of the above
Q.158 What is the purpose of a bioreactor controller's output signal?
To command an actuator
To measure a process variable
To set a setpoint
To log data
Explanation - The controller output drives an actuator to adjust the process variable.
Correct answer is: To command an actuator
Q.159 Which of the following is NOT a typical function of a controller in a bioreactor?
Receive sensor inputs
Calculate control output
Actuate valves and pumps
Log historical data
Explanation - Logging is usually handled by a historian or separate data acquisition system.
Correct answer is: Log historical data
Q.160 The term 'dead time' in process control refers to:
Time delay between controller output and process response
Time delay between sensor input and controller input
Time a sensor takes to calibrate
Time a bioreactor needs to fill
Explanation - Dead time is the lag between a control action and the observed effect.
Correct answer is: Time delay between controller output and process response
Q.161 Which of the following is a typical signal conditioning device used with temperature probes?
Amplifier
Filter
Rectifier
All of the above
Explanation - Signal conditioners can amplify, filter, or rectify the low-level output of a probe.
Correct answer is: All of the above
Q.162 What is the main purpose of a DO probe in a bioreactor?
Measure dissolved oxygen concentration
Measure temperature
Measure pH
Measure pressure
Explanation - A DO probe provides real‑time data on oxygen availability in the culture.
Correct answer is: Measure dissolved oxygen concentration
Q.163 Which of the following best describes a 'feedback' controller?
Acting after the error occurs
Acting before the error occurs
Using open‑loop operation
Using pre‑set schedules
Explanation - Feedback control reacts to sensor measurements to reduce the error.
Correct answer is: Acting after the error occurs
Q.164 Which of the following is an example of a bioprocess safety instrumentation?
Pressure relief valve
Temperature probe
Oxygen probe
pH electrode
Explanation - It protects the system from over‑pressurization.
Correct answer is: Pressure relief valve
Q.165 A bioreactor controller that adjusts aeration based on DO readings is an example of:
PID controller
Feedforward controller
Open‑loop controller
Manual controller
Explanation - PID controllers use DO feedback to regulate aeration and agitation.
Correct answer is: PID controller
Q.166 What is the typical output signal of a standard temperature probe?
Voltage
Current
Digital pulse
All of the above
Explanation - Temperature probes generate a voltage proportional to temperature changes.
Correct answer is: Voltage
Q.167 What does the 'integral' action in a PID controller primarily address?
Steady‑state error
Overshoot
Response time
Noise filtering
Explanation - The integral term accumulates error over time, driving the steady‑state error to zero.
Correct answer is: Steady‑state error
Q.168 Which of the following is a typical measurement used to monitor cell growth in a bioreactor?
Optical density
pH
Temperature
Oxygen concentration
Explanation - OD is a quick estimate of cell concentration by measuring light scattering.
Correct answer is: Optical density
Q.169 In a bioprocess, which sensor would you use to monitor the dissolved oxygen concentration?
pH electrode
Temperature probe
DO probe
Pressure transducer
Explanation - A DO probe directly measures oxygen concentration in the medium.
Correct answer is: DO probe
Q.170 A bioreactor's temperature control loop typically uses which type of sensor?
Thermocouple
pH electrode
Oxygen probe
Pressure transducer
Explanation - Thermocouples provide voltage proportional to temperature differences.
Correct answer is: Thermocouple
Q.171 Which of the following is a key function of a process historian in a bioreactor?
Log time‑series data
Control temperature
Calibrate sensors
Maintain pH
Explanation - Historians collect and store data for analysis, compliance, and troubleshooting.
Correct answer is: Log time‑series data
Q.172 Which of the following best describes the 'deadband' concept in a control system?
A range where the controller does not act
The maximum error before action
The time delay in the system
The type of sensor used
Explanation - Deadband prevents small deviations from triggering controller action.
Correct answer is: A range where the controller does not act
Q.173 What is the purpose of a temperature probe in a bioreactor?
Measure temperature
Measure pH
Measure dissolved oxygen
Measure pressure
Explanation - Temperature probes provide data for temperature control loops.
Correct answer is: Measure temperature
Q.174 Which of the following is a typical sensor used to measure dissolved oxygen?
Clark electrode
Thermocouple
pH electrode
Pressure transducer
Explanation - Clark electrodes are widely used for DO measurement.
Correct answer is: Clark electrode
Q.175 What does the 'proportional' term of a PID controller do?
Responds to the current error magnitude
Eliminates steady‑state error
Predicts future error
Introduces a time delay
Explanation - The proportional term is directly proportional to the error at the instant.
Correct answer is: Responds to the current error magnitude
Q.176 In a bioreactor, what is the primary function of a level sensor?
Measure liquid height
Measure temperature
Measure dissolved oxygen
Measure pH
Explanation - Level sensors monitor liquid volume to avoid overflow or under‑fill.
Correct answer is: Measure liquid height
Q.177 Which of the following is NOT typically part of a bioreactor instrumentation set?
Temperature probe
pH electrode
Oxygen probe
Wind speed sensor
Explanation - Wind speed has no relevance to bioprocess monitoring.
Correct answer is: Wind speed sensor
Q.178 Which of the following is a typical input to a bioreactor controller?
Process variable
All of the above
Proportional gain
Ambient humidity
Explanation - Controllers use the measured PV, setpoint, and internal parameters.
Correct answer is: All of the above
Q.179 Which of the following best describes the deadband in a control loop?
The range where the controller does not act
The maximum error before action
The time delay in the system
The type of sensor used
Explanation - Deadband prevents controller action for minor deviations.
Correct answer is: The range where the controller does not act
Q.180 What is the typical output signal of a standard pH electrode?
Voltage
Current
Digital pulse
All of the above
Explanation - pH electrodes generate voltage proportional to hydrogen ion activity.
Correct answer is: Voltage
Q.181 Which component is responsible for converting a sensor's electrical signal into an actuator command?
Controller
Actuator
Sensor
Power supply
Explanation - The controller processes the sensor input and generates a control output.
Correct answer is: Controller
Q.182 Which of the following best describes the 'integral' action in a PID controller?
Reduces steady‑state error
Increases overshoot
Accelerates response
Adds noise
Explanation - The integral term accumulates error over time to drive the steady‑state error to zero.
Correct answer is: Reduces steady‑state error
Q.183 Which sensor is used to measure temperature in a bioreactor?
Thermocouple
pH electrode
Oxygen probe
Pressure transducer
Explanation - Thermocouples produce voltage proportional to temperature differences.
Correct answer is: Thermocouple
Q.184 What is the purpose of a bioreactor's temperature control system?
Maintain a constant temperature
Maintain a constant pressure
Maintain a constant dissolved oxygen concentration
Maintain a constant pH
Explanation - Temperature control keeps the process within the desired range.
Correct answer is: Maintain a constant temperature
Q.185 Which of the following is NOT a typical function of a controller in a bioreactor?
Receive sensor inputs
Calculate control output
Actuate valves and pumps
Log historical data
Explanation - Logging is typically handled by a historian.
Correct answer is: Log historical data
Q.186 Which of the following sensors is most commonly used for monitoring dissolved oxygen?
pH electrode
DO probe
Temperature probe
Pressure transducer
Explanation - DO probes measure the oxygen concentration directly in the culture medium.
Correct answer is: DO probe
Q.187 What does a 'setpoint' refer to in process control?
Desired target value
Measured process variable
Controller output
Error signal
Explanation - Setpoint is the value the controller strives to maintain.
Correct answer is: Desired target value
Q.188 Which of the following is a typical sensor used to measure the pH of a bioreactor?
pH electrode
Temperature probe
Oxygen probe
Pressure transducer
Explanation - A pH electrode measures the acidity or alkalinity of the solution.
Correct answer is: pH electrode
Q.189 Which of these is a typical parameter monitored in a bioreactor process?
Temperature
pH
Cell density
All of the above
Explanation - Temperature, pH, and cell density are essential for controlling the bioprocess environment.
Correct answer is: All of the above
Q.190 What is the main advantage of a 4‑20 mA current loop in bioprocess instrumentation?
High noise immunity over long cables
Simple voltage amplification
High voltage operation
Large bandwidth
Explanation - Current loops are robust against voltage drops and electromagnetic interference.
Correct answer is: High noise immunity over long cables
Q.191 Which component is primarily responsible for converting a sensor's electrical signal into an actuator command?
Sensor
Actuator
Controller
Power supply
Explanation - The controller processes the sensor input and generates an output for the actuator.
Correct answer is: Controller