A. The ECG signal of a person shows an irregular heartbeat of 180 beats per minute. You areasked to come up with a system that digitises this signal, using an analog-to-digitalconverter (ADC) with a reference voltage of 5 V. The digitised signal should have a resolutionof 1 mV or better.i) How many samples per second should your system take in order to fully capture the ECGsignal?ii) What should the ADC’s resolution in bits be? Alternatively, how many quantisation levelsshould the ADC have; or how many bits per sample should the ADC have? B. You have successfully designed your ECG signal capture device. However, the person fromQuestion A is being examined in a room with fluorescent lights which have recently startedbuzzing. The digitised ECG signal appears to be very noisy, and the medical doctors arefinding it difficult to diagnose the patient. You suspect interference from the electrical mainsis to blame.You also notice that the ECG signal is very faint and not making full use of your ADC. Youmeasure its maximum amplitude to be 15 mV. i) How would you solve the problem of electrical mains interference? What type ofcomponent would you add to your device?ii) How would you make sure that the signal uses the full range of the ADC (0 – 5 V) ratherthan the much more limited (0 – 15 mV)? What type of component would you add to yourdevice, and what will be the value of its main parameter?
A. The ECG signal of a person shows an irregular heartbeat of 180 beats per minute. You are
asked to come up with a system that digitises this signal, using an analog-to-digital
converter (ADC) with a reference voltage of 5 V. The digitised signal should have a resolution
of 1 mV or better.
i) How many samples per second should your system take in order to fully capture the ECG
signal?
ii) What should the ADC’s resolution in bits be? Alternatively, how many quantisation levels
should the ADC have; or how many bits per sample should the ADC have?
B. You have successfully designed your ECG signal capture device. However, the person from
Question A is being examined in a room with fluorescent lights which have recently started
buzzing. The digitised ECG signal appears to be very noisy, and the medical doctors are
finding it difficult to diagnose the patient. You suspect interference from the electrical mains
is to blame.
You also notice that the ECG signal is very faint and not making full use of your ADC. You
measure its maximum amplitude to be 15 mV.
i) How would you solve the problem of electrical mains interference? What type of
component would you add to your device?
ii) How would you make sure that the signal uses the full range of the ADC (0 – 5 V) rather
than the much more limited (0 – 15 mV)? What type of component would you add to your
device, and what will be the value of its main parameter?
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