week 4.1

Question 1

biosignals

Answer 1

variations in energy as a function of space and time

Question 2

what is a measured signal composed of?

Answer 2

biosignal of interest and noise

(biosignal of interest is the device recording the signal, like ECG, EKG, etc)

Question 3

noise

Answer 3

any variation to quantity being measured not related to process of interest

Question 4

encoding

Answer 4

part of processing measured signal, can be divided into coninuous (analog) and discrete (digitial)

Question 5

continous/analog signal

Answer 5

information is coded in terms of amplitude
signal has defined amplitude at every point in domain

dumbed down: the y is amplitude and signal is always being measured

Question 6

what is the domain of a continuous/analog signal?

Answer 6

it’s uncountable and may or may not be finite. signal will have some value at every point
-> function doesn’t need to be continous

Question 7

examples of continuous/analog signal

Answer 7

temperature, sine wave, etc

Question 8

discrete/digital signal

Answer 8

defined over a discrete time domain, therefore has a countable domain

Question 9

signal measurement system

Answer 9

analog to digital
sampling is done by slicing up to sequence digital numbers at time intervals Ts

dumbed down: chop up analog into time intervals (Ts) for digital

Question 10

most biosignals are digitized by the data collection system:

Answer 10

data acquisition and analog to digital conversion

Question 11

digital signals is a series of…

Answer 11

numbers
x[k] = x0, x1, x2, x3, x4… xN

Question 12

what does x[k] represent?

Answer 12

the value of the analog signal at discrete points in time

Question 13

how is the sample interval (Ts) determined

Answer 13

t = n * Ts = n / fs

Question 14

what is fs

Answer 14

sampling frequency
fs = 1/ Ts

Question 15

what is n

Answer 15

position of the number in the sequence

Question 16

digitizing of analog signal

Answer 16

requires slicing of signal in time and amplitude

Question 17

what is the functions of analog and digital signals?

Answer 17

analog: x(t), x is a function of time
digital: x[n], x is a function of sampled numbers n

Question 18

analog to digital (A/D board)

Answer 18

16 bit, multifunction I/O device

Question 19

LSB

Answer 19

least significant bit, minimum change in voltage required to guarantee a change in output
(measure of accuracy)

Question 20

V LSB equation

Answer 20

V LSB = V max / 2^Nbits - 1

Question 21

systematic error

Answer 21

each measurement deviates from true value by a fixed amount

Question 22

random error

Answer 22

noise: unpredictable variations in measured signal from moment to moment

Question 23

examples of noise

Answer 23

building vibrations, air currents, electric power fluctuations, stray radiation from nearby electricals

Question 24

physiological variability noise

Answer 24

what you’re measuring can vary from other mechanisms
solution: modify approach

Question 25

environmental noise or interference

Answer 25

caused by other source of similar energy effecting signal of interest
ex: fetal ECG signal is corrupted by mother’s ecg signal

Question 26

arifiact

Answer 26

caused by transducer response to other energy variation
ex: motion artifact, stimulus artifact

solution: design better transducers

Question 27

electronic noise

Answer 27

caused by known sources and characteristics
ex: white noise
solution: transducer/electronic design

Question 28

two sources of electronic noise

Answer 28

thermal or johnson noise (resistors
shot noise (current noise, like voltage barriers of semiconductors)

Question 29

white noise

Answer 29

has similar energy levels over all frequencies range

Question 30

error can be calculated by

Answer 30

subtracting mean from the original data set

Question 31

variance

Answer 31

signal variability irrespective of its average

matlab command var(x)

Question 32

standard deviation

Answer 32

square root of variance

Question 33

sinusoidal

Answer 33

a sign graph

periodic signal = x(t) = x(t + T)
t = time
T =period in seconds

Question 34

what information about the variability of a signal does the average provide?

Answer 34

None. it does not give us any info

Question 35

root mean squared (RMS) acronym

Answer 35

S quare the signal
M ean (calculate)
R oot (sqrt)

Question 36

effective value (RMS) of AC voltage is ___ to the DC voltage

Answer 36

equivalent

Question 37

does a lamp with 6V rms AC supply have the same brightness as a lamp with 6V DC supply

Answer 37

yes