BCIA Instrumentation & Technology 2 — Questions and Answers
Question 1: What type of sensor is used to measure skin conductance (EDA) in biofeedback?
- Thermistor
- Strain gauge
- Ag/AgCl electrodes (Correct answer)
- Piezoelectric sensor
Correct answer: Ag/AgCl electrodes
Silver/silver chloride (Ag/AgCl) electrodes are the standard for measuring electrodermal activity due to their stable half-cell potential.
Question 2: A photoplethysmograph (PPG) sensor measures peripheral blood flow using which method?
- Electrical impedance
- Light absorption changes in tissue (Correct answer)
- Pressure wave detection
- Infrared thermography
Correct answer: Light absorption changes in tissue
PPG sensors shine light into tissue and detect changes in light absorption caused by pulsatile blood volume changes.
Question 3: In biofeedback instrumentation, what does 'common mode rejection ratio' (CMRR) indicate?
- The ability to filter high-frequency noise
- How well the amplifier rejects signals common to both inputs (Correct answer)
- The gain of the amplifier
- The bandwidth of the filter
Correct answer: How well the amplifier rejects signals common to both inputs
A high CMRR indicates the amplifier effectively cancels electrical interference that appears equally on both input leads.
Question 4: Respiration biofeedback transducers most commonly use which mechanism?
- Photoelectric sensing
- Strain gauge or piezoelectric stretch sensor (Correct answer)
- Thermistor in the nares
- Pressure cuff
Correct answer: Strain gauge or piezoelectric stretch sensor
Strain gauge or piezoelectric sensors attached to a chest or abdominal belt detect respiratory excursion through mechanical stretch.
Question 5: What is the primary advantage of using wireless biofeedback sensors during ambulatory sessions?
- They provide higher signal fidelity than wired sensors
- They allow monitoring in natural environments without restricting movement (Correct answer)
- They eliminate the need for electrode gel
- They reduce session cost significantly
Correct answer: They allow monitoring in natural environments without restricting movement
Wireless sensors enable ambulatory biofeedback, letting clinicians assess and train physiology in real-world settings without tethering the client.
Question 6: Which filter type is used to remove slow baseline drift from biofeedback signals?
- Low-pass filter
- High-pass filter (Correct answer)
- Notch filter
- Band-pass filter
Correct answer: High-pass filter
A high-pass filter attenuates very low frequencies, removing slow baseline drift while preserving the biosignal of interest.
BCIA Instrumentation & Technology 2
What type of sensor is used to measure skin conductance (EDA) in biofeedback?