week 4.2

Question 1

discrete signal

Answer 1

X[k] the value of an analog signal at discrete points in tiem

Question 2

every point in time of a discrete signal is determined by the…

Answer 2

sample interval (Ts)

Question 3

t =

Answer 3

n*Ts = 1/ Fs

Question 4

Fs

Answer 4

sampling frequency
1 / Ts

Question 5

N

Answer 5

position of number in the sequence

Question 6

analog vs digital

Answer 6

analog is continous while digital is interval based
continuous is amplitude vs time
discrete is amplitude based on sample number

Question 7

sinosuidal

Answer 7

having sin wave

Question 8

RMS defintion

Answer 8

calculates mean based on magnitude of numbers, not sign

Question 9

ratio for comparing intensity of two signals

Answer 9

V signal one / V signal 2 (units dB)

Question 10

comparing power of two signals

Answer 10

Pdb = 10log(p1/ p2)

Question 11

comparing voltage of two signals (RMS)

Answer 11

p = v^2/R

Question 12

SNR

Answer 12

signal to noise ratio

Question 13

the ___ the SNR, the better the signal

Answer 13

larger

Question 14

convert SNR to linear

Answer 14

10^ (SNRdb / 20)

Question 15

if SNR is positive the signal is ___ than the noise

Answer 15

stronger

Question 16

if SNR is negative, the signal is ___ than the noise

Answer 16

weaker

Question 17

steps of biosignal measurement system

Answer 17

signal
sensor/transducer
signal processing
analog to digital converter
display/storage
post processing
analysis
interpretation

Question 18

sensor/transducer

Answer 18

transduce biosignal to electrical one (still analog)

Question 19

signal processing

Answer 19

process/condition signal to reduce noise and prepare for digitization
amplify, filter, shift

Question 20

amplify signal

Answer 20

multiply by constant at every point in time or spae

Question 21

filter signal

Answer 21

multiply by function in frequency domain

Question 22

shift signal

Answer 22

add constant at every point in time or space

Question 23

analog to digital converter

Answer 23

digitize by sampling continuous signal and discretizing the signal at each time/frq domain

choose the appropriate sampling rate
- fill input range of digitizer to max resolution

Question 24

discretization

Answer 24

rounding to a number of finite precision

Question 25

post processing

Answer 25

noise reduction with digital filters, averaging, FFT, down sampling

Question 26

EMS recording system

Answer 26

device that connects electrodes to muscles and collects data when muscle is activated (ex: changing in length)

Question 27

motor commands to muscle are transmitted through..

Answer 27

changes in electrical potential

Question 28

EMS recording system records…

Answer 28

the difference in potential between two electrodes

Question 29

sEMGs

Answer 29

have max amplitude of 5V, internal has 10V

*10V is better but you need to insert needle in patient which isn’t convenient

Question 30

aliasing

Answer 30

when signal is discreetly sampled at an insufficient rate to capture changes in signal

i.e bad time intervals and inconsistent data

Question 31

best approximation of signal is when…

Answer 31

you sample the signal multiple times per cycle

Question 32

in aliasing, components of digitized signal at high frq are mistaken for..

Answer 32

components at low frequencies

Question 33

how to avoid aliasing?

Answer 33

sample rate should be greater than or equal to twice the highest frequency present in the signal

Fs^3 = 2Fc
(Fs is sampling frq and Fc is highest frq in signal)