BTC Biomedical Instrumentation & Electrical Fundamentals 1 — Questions and Answers
Question 1: According to AAMI ES1 standards, what is the maximum allowable leakage current for chassis ground of patient-connected (Type CF) equipment?
- 10 microamps
- 50 microamps (Correct answer)
- 100 microamps
- 500 microamps
Correct answer: 50 microamps
AAMI ES1 specifies a maximum chassis leakage current of 50 microamps for Type CF (cardiac-floating) patient-connected equipment under normal conditions.
Question 2: A biomedical technician measures 12 volts across a 4-ohm resistor. According to Ohm's Law, what current is flowing through the resistor?
- 0.33 amps
- 1.5 amps
- 3 amps (Correct answer)
- 48 amps
Correct answer: 3 amps
Ohm's Law states I = V/R; dividing 12 volts by 4 ohms yields 3 amps.
Question 3: In a biomedical circuit, a capacitor is used in parallel with a load. What is the primary function of the capacitor in this configuration?
- Amplify the signal voltage
- Filter high-frequency noise from the power supply (Correct answer)
- Increase resistance to protect the load
- Convert AC to DC current
Correct answer: Filter high-frequency noise from the power supply
A capacitor placed in parallel across a load acts as a bypass or decoupling capacitor, filtering high-frequency noise and smoothing voltage ripple.
Question 4: When testing a defibrillator, which measurement is used to verify the energy delivered to the patient?
- Peak voltage only
- Delivered energy in joules (Correct answer)
- Charge voltage in millivolts
- Average current in milliamps
Correct answer: Delivered energy in joules
Delivered energy in joules is the standard measurement for verifying defibrillator output because it represents the actual therapeutic energy transferred to the patient.
Question 5: A Wheatstone bridge circuit is commonly used in biomedical instrumentation to measure what type of parameter?
- Frequency of AC signals
- Small changes in resistance from transducers (Correct answer)
- Amplitude of digital signals
- Capacitance of isolation transformers
Correct answer: Small changes in resistance from transducers
The Wheatstone bridge is designed to detect small changes in resistance, making it ideal for use with strain gauges, thermistors, and other resistive transducers in biomedical devices.
Question 6: An operational amplifier (op-amp) configured in inverting mode with a feedback resistor of 100 kΩ and an input resistor of 10 kΩ has a voltage gain of:
- +10
- -10 (Correct answer)
- +0.1
- -0.1
Correct answer: -10
In an inverting op-amp configuration, gain = -(Rf/Rin) = -(100kΩ/10kΩ) = -10, meaning the output is inverted and ten times the input amplitude.
Question 7: A Ground Fault Circuit Interrupter (GFCI) protects personnel in the biomedical environment by tripping when it detects a ground fault current exceeding:
- 1 milliamp
- 5 milliamps (Correct answer)
- 10 milliamps
- 50 milliamps
Correct answer: 5 milliamps
A standard GFCI trips when an imbalance of approximately 5 milliamps is detected between the hot and neutral conductors, indicating current leaking to ground.
BTC Biomedical Instrumentation & Electrical Fundamentals 1
According to AAMI ES1 standards, what is the maximum allowable leakage current for chassis ground of patient-connected (Type CF) equipment?