BME520: Biomedical Device Troubleshooting
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BME520: Biomedical Device Troubleshooting

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@PreferableHazel

Questions and Answers

What is the effect of increasing the input resistance Rlim on the current in the front-end component?

  • It has no effect on the current.
  • It decreases both the current and noise power.
  • It decreases the current but increases noise power. (correct)
  • It increases the current significantly.
  • What must circuit protection devices do to avoid failure in the devices they protect?

  • They must switch to the conducting state quickly. (correct)
  • They must have zero resistance.
  • They must be able to generate high noise levels.
  • They must maintain a constant current.
  • What causes thermal Johnson noise in conductors?

  • Electric potential difference.
  • Brownian motion of carriers. (correct)
  • Magnetic fields around the conductor.
  • Electrostatic forces within the material.
  • How does the root mean square (rms) value of noise voltage relate to temperature and resistance?

    <p>It is proportional to temperature and resistance.</p> Signup and view all the answers

    What physical constant is used in the formula for calculating Johnson Noise?

    <p>Boltzmann’s constant.</p> Signup and view all the answers

    What might cause false alarms in biomedical devices?

    <p>Termination of intended operations</p> Signup and view all the answers

    Which of the following is a potential cause of changes in internal memory leading to false alarms?

    <p>Parameter changes</p> Signup and view all the answers

    What kind of failure might occur in the PCB affecting device functionality?

    <p>Opening of PCB tracks</p> Signup and view all the answers

    Which requirement is outlined by IEC/EN 60601-1-2 regarding electromagnetic interference?

    <p>Immunity requirements for conducted/radiated EMI</p> Signup and view all the answers

    What effect can over-voltage have on biomedical devices?

    <p>Exceeds maximum allowed values of connected components</p> Signup and view all the answers

    Study Notes

    Circuit Protection Function

    • False alarms can occur due to a variety of factors, including operational terminations, incorrect parameter changes, mode switch errors, and component failures such as PCB short circuits.
    • IEC/EN 60601-1-2 outlines immunity requirements for biomedical devices against conducted and radiated electromagnetic interference (EMI).
    • Over-voltage conditions can lead to excessive current or voltage on components connected to input/output lines, necessitating quick transitions to protect devices.
    • Increasing input resistance reduces current but can raise noise power (Johnson Noise), potentially affecting signal integrity for sensitive applications.

    Johnson Noise

    • Thermal Johnson noise arises from the random motion of charge carriers in a conductor, generating noise voltage proportional to temperature and resistance.
    • Key formula: RMS noise voltage is influenced by Boltzmann’s constant, resistance in ohms, temperature in kelvin, and measurement bandwidth in hertz.

    Transient Voltage Suppressors

    • Voltage clamping technologies are essential for protecting sensitive electronics from voltage spikes.

    Buffer Stage

    • Buffers in biomedical devices must feature high input impedance (≥ 2.48MΩ) to accommodate high source impedances common in ECG applications to minimize measurement errors.
    • Essential buffer stage requirements include input impedance, maximum over-voltage tolerance, input dynamic range, noise contribution, and frequency response.

    Op-Amp Applications

    • Operational amplifiers (op-amps) facilitate analog interfacing in medical devices, serving critical roles in ECG, EEG, and other medical monitoring equipment.
    • Variants designed for low power consumption are available, suitable for battery-operated devices.
    • Specific applications of op-amps include instrumentation for ECG/EEG monitoring with high common-mode rejection ratios and buffers in photodiode circuits, such as glucose meters.

    Analog Filters

    • Analog filters modify signals through hardware to improve their quality before processing, avoiding the latency associated with digital filtering techniques.
    • Digital filters often introduce delays as they require computational processing of analog data.

    ADC Conversion

    • Analog-to-digital converters (ADC) serve as essential interfaces for transitioning analog signals into a digital format, enabling further processing.

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    Description

    Test your knowledge on troubleshooting biomedical devices with this quiz. It covers critical aspects such as false alarms, termination of operations, parameter changes, and component failures. Perfect for students in Biomedical Systems and Informatics Engineering.

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