Questions and Answers
What is the effect of increasing the input resistance Rlim on the current in the front-end component?
What must circuit protection devices do to avoid failure in the devices they protect?
What causes thermal Johnson noise in conductors?
How does the root mean square (rms) value of noise voltage relate to temperature and resistance?
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What physical constant is used in the formula for calculating Johnson Noise?
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What might cause false alarms in biomedical devices?
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Which of the following is a potential cause of changes in internal memory leading to false alarms?
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What kind of failure might occur in the PCB affecting device functionality?
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Which requirement is outlined by IEC/EN 60601-1-2 regarding electromagnetic interference?
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What effect can over-voltage have on biomedical devices?
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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.
