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1. CNIM Exam Review Material
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1. CNIM Exam Review Material ...
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Coulomb's Law - ANSWER The force exerted between two charges is inverselyproportional to
the square of the distance between them.
F=1/(distance)^2
Voltage - ANSWER an electromotive force or potential difference expressed in volts.
1. CNIM Exam Review Material 2024-2025
Current - ANSWER Movement of charge (Amps)
Ohm's Law - ANSWER V=IR
Resistance is opposition to ____
Impedance is opposition to ____ - ANSWER Resistance is opposition to DC flow
Impedence is opposition to AC flow
Resistors in Series (Voltage Divider)
Resistors in Parallel (Current Divider)
-What stays the same and what divides? - ANSWER Series - Current is the same, voltage
divides among the resistors Rtotal = R1+R2
Parallel- Voltage is the same, current divides among the resistors 1/Rtotal = 1/R1 + 1/R2
Cutoff frequency - ANSWER Fcutoff = 1/2 π τ
,Where τ= resistance * capacitance (in farads)
Inductance
-What is it?
What does this lead to in our recording? - ANSWER From the principle that flow of
current produces a magnetic field, which can then induce an electric current.
Electromagnetic fields created by devices like powercords and blood warmers can
easily induce current within our recording wire due to the closeness, manifesting as 60
hz noise artifact
Gain of Differential Amplifier - ANSWER Gain = Vout/Vin
Common Mode Rejection Ratio (CMRR) - ANSWER the ability of the differential amplifier
to reject the common noise between the active electrodes
Guidelines: Ratio of 10,000:1 or 80 dB
Input Impedence - ANSWER Impedance of amplifiers patient inputs
Guidlines: Greater than or equal to 100 Mohms
Filters
-Cutt off Frequency? What % amplitude is reduced?
-Mnemonic for remembering the effects of filtering on latencies?
-Effects of filtering on signals latency? - ANSWER Cutoff: the freq where there is 3dB or
30% reduction in signals amplitude
'Lower means longer':
-Decreasing (lowering) the hicut will increase (longer) the signals latency
-Increasing (raising) the lowcut will decrease (shorten) the signals latency
,Phase effects/ Latency shift
-How do these occur?
-What is a positive aspect of digital filters? - ANSWER Phase effects can occur if an
analog filter has an overly-steep roll-off.
Digital filters do not have phase effects.
What are 60 notch filters capable of?
-Shall we employ these? - ANSWER 1. Ringing Effect
2. Latency Shifts
3. Morphology changed
-NO! Use at all costs!
Horitzontal resolution
-What axis?
-What is sampling rate?
-what is Bin Width/Dwell time? Guidelines? - ANSWER -resolving a waveform on time
axis
Sampling rate: the rate (in points per second) that the A-D converter assigns discrete
points to an analog signal
Bin width (aka dwell time): 1/sampling rate (inversely proportional)
Guidelines: require bin width to be <20uS/data point (sampling rate >50,000)
Aliasing
-What is it?
-How can it be avoided? - ANSWER Aliasing: misrepresentation of an analog waveform
due to sampling too slowly
-Can be avoided by sampling at Nyquist Freq or higher (aka 2x fastest freq in recorded
, signal)
Vertical resolution
-What axis?
-What number of discrtete pts determined?
-Guidelines?
- What if range too big or too small? - ANSWER Vertical: voltage axis resolution
# of discrete pts available is determined by # bits; = 2^N (N= bits)
Rules of thumb: minimum of 8 bits
Range:
-Too small of a range= waveform clipping
-Too large of a range= leads to lower resolution with distortion of signal
SNR
-What is it and what improves it?
- How to calculate SNR at any average?
-How to calculate noise at any given average? - ANSWER Signal to noise ratio
SNR= Amplitutde of signal/Amplitude of the noise
Calculating at any average:
SNRfinal= SNRinitial (√n)
Noisefinal= Noiseinitial/(sqrt(# of averages)
Synchronous Stimulation
-What is it and what can it increase?
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