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Questions and Answers
What effect does twisting lead wires together have in minimizing interference?
What effect does twisting lead wires together have in minimizing interference?
What is the purpose of voltage-limiting devices in an electrocardiograph?
What is the purpose of voltage-limiting devices in an electrocardiograph?
Which component is commonly used as a voltage-limiting device?
Which component is commonly used as a voltage-limiting device?
How does common-mode voltage affect biomedical circuits?
How does common-mode voltage affect biomedical circuits?
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Which circuit element is NOT typically used for voltage limiting?
Which circuit element is NOT typically used for voltage limiting?
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What is the primary function of a transient-voltage-suppression (TVS) diode?
What is the primary function of a transient-voltage-suppression (TVS) diode?
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In a driven-right-leg (DRL) system, how is common-mode voltage derived?
In a driven-right-leg (DRL) system, how is common-mode voltage derived?
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What type of interference can a driven-right-leg (DRL) circuit help minimize?
What type of interference can a driven-right-leg (DRL) circuit help minimize?
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Which component is NOT typically considered a reactive component in circuits?
Which component is NOT typically considered a reactive component in circuits?
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What is one method used to protect sensitive biomedical devices from electrical spikes?
What is one method used to protect sensitive biomedical devices from electrical spikes?
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Which interference source is most likely to affect bio-potential measurements?
Which interference source is most likely to affect bio-potential measurements?
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What characteristic of electronic circuits can be attributed to reactive components?
What characteristic of electronic circuits can be attributed to reactive components?
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Which function does a resistor fulfill in a DRL circuit?
Which function does a resistor fulfill in a DRL circuit?
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What primarily causes artifacts in an ECG during cardiac defibrillation?
What primarily causes artifacts in an ECG during cardiac defibrillation?
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What type of interference is represented in Figure 6.9 (a)?
What type of interference is represented in Figure 6.9 (a)?
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Which factor can lead to variability in electrode impedance affecting ECG readings?
Which factor can lead to variability in electrode impedance affecting ECG readings?
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What method is typically recommended to reduce electric-field pickup in electrocardiographs?
What method is typically recommended to reduce electric-field pickup in electrocardiographs?
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What is a significant source of common-mode voltage in ECG measurements?
What is a significant source of common-mode voltage in ECG measurements?
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Which type of components are crucial for protecting circuits from voltage transients?
Which type of components are crucial for protecting circuits from voltage transients?
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Which issue is commonly caused by magnetic-field pickup in electrocardiography?
Which issue is commonly caused by magnetic-field pickup in electrocardiography?
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What can an amplifier experience due to unexpected voltage transients?
What can an amplifier experience due to unexpected voltage transients?
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Study Notes
Change in Magnetic Field and Current Induction
- Change in magnetic field through a loop induces current in the circuit.
- Minimization of induced current effects achieved by twisting lead wires together, keeping them close to body to reduce the subtended area.
Transient Protection in Electrocardiographs
- Voltage-protection scheme at electrocardiograph inputs safeguards against high-voltage transients.
- Voltage-limiting devices connected across limb leads protect the apparatus from voltage spikes.
Voltage-Limiting Devices
- Various circuits for voltage-limiting include:
- Current-voltage characteristics of a basic voltage-limiting device.
- Parallel silicon-diode circuits.
- Back-to-back silicon zener-diode circuits.
- Gas-discharge tube (neon light) circuits.
Transient-Voltage-Suppression (TVS) Diode
- TVS diodes protect sensitive electronic devices from voltage spikes along wires.
- Acts as a safety mechanism for electronics in high-voltage situations.
Driven-Right-Leg (DRL) System
- DRL system minimizes common-mode interference in ECG readings.
- Utilizes averaging resistors to derive common-mode voltage, improving fidelity in readings.
Artifacts from Electric Transients
- Defibrillation can induce voltage transients affecting ECG signals.
- Transient effects can cause amplifier saturation, requiring a recovery period to restore proper function.
Problems with Electric Device Interference
- Common interference includes 60 Hz power-line and electromyographic disturbances on ECG recordings.
- For example, with a 9 m cable, detected interference current can be approximately 6 nA due to varying electrode impedance (up to 20 kΩ).
- Shielding leads effectively minimizes electric-field pickup from surrounding electrical devices.
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Description
Explore the principles of current induction through changing magnetic fields and the various voltage-limiting devices used in electrocardiographs. This quiz covers transient protection methodologies and the function of transient-voltage-suppression diodes in safeguarding electronic devices from voltage spikes.
