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CNIM Instrumentation
questions and answers 2025-
2026(latest update with
verified solutions)
A unit of resistance is symbolized by A- A B- ohms C- E D- micro - answer B- ohms The capacity to resolve amplitudes of 256 discrete steps would require an 8 bit A to D converter. This can be represented by: A- 8 B- 8/ C- 256 D- 2^8 - answer D- 2^ What is the minimum required bandpass for an EP system? A- 1 - 1000 Hz B- 0.1 ‐ 5000 Hz C- 30 ‐ 1500 Hz D- 1 Hz - 20 KHz - answer B- 0.1 ‐ 5000 Hz The gain of an amplifier, set to give an output signal of 1 volt for an input signal of 10 microV, is A- 100,
B- 10,
C- 100
D- 1,000 - answer A- 100, A 100 mS epoch is recorded with a 10 mS post ‐ stimulus triggering. Which of the following best describes the resulting sweep? A- A 100 mS sweep starting 10 mS after the stimulus B- A 90 mS sweep starting 10 mS after the stimulus C- A 100 mS sweep starting 10 mS prior to the stimulus D- A 110 mS sweep starting 10 mS prior to the stimulus - answer A- A 100 mS sweep starting 10 mS after the stimulus SSEP recordings typically require a bandpass of A- 1000 Hz to 5,000 Hz B- 30 Hz to 3,000 Hz C- 100 Hz to 1,000 Hz D- .5 Hz to 200 Hz - answer B- 30 Hz to 3,000 Hz To accurately represent the amplitude of an EP waveform, a match must be made between the A- dwell time and sampling rate B- signal size and the vertical capacity of the digitizer C- high‐frequency noise and smoothing operation of the instrument D- horizontal resolution and signal size - answer B- signal size and the vertical capacity of the digitizer In selecting the horizontal parameters of analysis, the A- sampling rate should be the equivalent of the highest frequency in the signal B- analysis period should be at least twice the Nyquist frequency
C- 1/2 the highest frequency D- twice as great as the highest frequency - answer D- twice as great as the highest frequency The following are examples of good insulating materials, inhibiting current flow: A- silicon and germanium B- glass and rubber C- gold and platinum D- silver and copper - answer B- glass and rubber "Electrode impedance" is defined as opposition to A- 60 Hz artifact B- direct current flow C- alternating current flow D- differential current flow - answer C- alternating current flow Dwell time can be defined as A- the D to A conversion B- the A to D conversion C- the intersample interval D- the sample rate of the signal's amplitude - answer C- the intersample interval If not specified, most reports on ABR are displayed: A- vertex positive down B- negativity up C- using "N" plus a number to designate a wave D- vertex positive up - answer D- vertex positive up
The difference between the voltages in input 1 and input 2 will make the display of the amplifier move: A- down B- up C- either up or down D- in a sinusoidal pattern - answer C- either up or down Nyquist Frequency A- Maximum stimulation repetition rate B- Minimum sampling rate to prevent aliasing C- One-half the highest frequency component of the signal measured D- Minimum stimulation repetition rate - answer B- Minimum sampling rate to prevent aliasing Cathode A- Positive input to the differential amplifier B- Positive pole or red dot on the bar electrode C- Used for recording EMG D- Negative pole or block dot on the bar electrode - answer D- Negative pole or block dot on the bar electrode Aliasing is the result of: A- High recording electrode impedance B- Low input impedance C- Sampling above the Nyquist frequency D- Sampling below the Nyquist frequency - answer D- Sampling below the Nyquist frequency
If a 10 microvolt signal inside 50 microvolts of noise is averaged for 100 traces, the final signal to noise ratio will be: A- 1: B- 1: C- 2: D- 5:1 - answer C- 2: An EP recording system should allow averaging of: A- 6000 trials or more B- a maximum of 2000 trials C- no more than 500 trials D- at least 4000 trials - answer D- at least 4000 trials The input impedance of a differential amplifier must be at least: A- 100 megaohms B- 10 megaohms C- 10 megaohms D- 5 Kohms - answer A- 100 megaohms When using constant voltage for facial nerve stimulation and the nerve becomes bathed in CSF, what will occur after the area is suctioned? A- The output voltage will vary to maintain a preset current level B- No change will occur C- The stimulator will stop D- The current flow will vary in order to maintain the preset voltage lever - answer D- The current flow will vary in order to maintain the preset voltage lever Reduction of the high frequency filter
A- has no effect on evoked potential latency B- decreases evoked potential latency C- increases evoked potential latency D- has an unpredictable effect on evoked potential latency - answer C- increases evoked potential latency "Prestimulus triggering" A- delays the synchronizing pulse to the computer B- presents a positive signal to the averaged prior to initiating the display C- includes a period of recording before the stimulus D- eliminates the problems associated with recording the stimulus artifact - answer C- includes a period of recording before the stimulus A constant voltage stimulator A- varies the output in order to maintain a preset current level B- maintains a current level of 10 mA C- maintains a constant voltage of 100 volts D- varies the current in order to maintain a preset voltage level - answer D- varies the current in order to maintain a preset voltage level Given an electrical circuit with a resistance of 1000 ohms and a voltage of 10 volts, the current flow will be: A- 10 A B- 100 volts C- 0.01 A D- 0.10 ohms - answer C- 0.01 A
"Signal-to-noise ratio" relates to which of the following? A- The ability of the instrument to resolve data and noise vertically B- The amplitude of the evoked response components to the amplitude of the unrelated components C- Sensitivity scaling D- Two inputs of a differential amplifier with like negativity - answer B- The amplitude of the evoked response components to the amplitude of the unrelated components If you have a small signal with a lot of noise what should you do to help resolve your signal? A- Increase your duration B- Increase your stimulus rate C- Increase your averages D- Increase you trigger delay - answer C- Increase your averages If you have a 5 μV signal amplitude and a 20 μV noise amplitude, how many averages would you need to get a signal to noise ratio of 2:1? A- 16 B- 64 C- 20 D- 100 - answer B- 64 The Gain of a differential amplifier is defined as: A- Output voltage divided by input voltage B- The voltage difference between the inputs C- Input voltage divided by output voltage
D- Output voltage minus input voltage - answer A- Output voltage divided by input voltage If you get artifact in you subcortical channel you: A- Use a spare CS5 electrode B- Ask anesthesia to increase gases C- Ask the surgeon to move retractors D- Disable the subcortical channel - answer A- Use a spare CS electrode The minimum required Common Mode Rejection Ratio of a differential amplifier is: A- 1,000: B- 10,000: C- 80: D- 10:1 - answer B- 10,000: The input impedance of a differential amplifier should be: A- Less than 5000 ohms B- At least 10,000 ohms C- At least 80 decibels D- At least 100 Megaohms - answer D- At least 100 Megaohms A differential amplifier with a Gain of 1,000,000 has a 0.2 μV signal at its positive input and a 0.8 μV signal at its negative input. The output will be: A- An upward peak of 1 V B- A downward peak of 1 V C- A downward peak of 0.6 V
C- Other metals become toxic when they contact the spinal cord D- Platinum is cost effective - answer A- Other metals become toxic when current is applied to them due to the ionic Lowering the SSEP hicut filter from 500 Hz to 200 Hz may cause the cortical peaks to: A- Appear larger in amplitude B- Appear longer in latency C- Appear shorter in latency D- Become insensitive to anesthesia - answer B- Appear longer in latency Which time constant would be most effective for cutting out low frequency noise from your signal? A- 100 ms B- 10 ms C- 10 s D- 1 s - answer B- 10 ms What is the required horizontal resolution of an evoked potential system? A- At least 8 bits per data point B- At least twice the Nyquist frequency C- 20 μS per data point of less D- At least 20 μS per data point - answer C- 20 μS per data point or less The Vertical Resolution of an evoked potential system depends primarily on: A- The analysis period
B- The filter settings C- The number of bits in the A/D Converter D- The sampling rate - answer C- The number of bits in the A/D Converter A 10-bit A/D Converter has how many discrete voltage values in its range? A- 256 B- 1024 C- 2048 D- 512 - answer B- 1024 What is the minimum required vertical resolution of an evoked potential system? A- 256 bits B- 8 bits C- 16 bits D- 80 bits - answer B- 8 bits A match must be made between the size of the recorded signal and the range of the A/D Converter: A- To accurately represent the amplitude of the signal B- To prevent unnecessary artifact rejection C- To accurately measure the latency of a peak D- To prevent aliasing of the signal - answer A- To accurately represent the amplitude of the signal Why do we use electrodes with the same metals? A- To get electrode polarization B- To ensure low impedance
B- Have difficulty stimulating the underlying nerve C- Create a lethal pathway for current D- Max out your impedances - answer B- Have difficulty stimulating the underlying nerve If an evoked potential has a voltage of 10uV and the associated noise has a voltage of 50uV, what is the signal-tonoiseratio after 100 averaged responses? A- 2: B- 1: C- 5: D- 1:1 - answer A- 2: To display median nerve SSEP response as an upward deflection, which of the following must be known? A- Polarity convention of amplifier inputs and amplitude of the response B- Waveform polarity and polarity convention of the amplifier inputs C- Latency of the response and polarity convention of the amplifier inputs D- Waveform polarity and latency of the response - answer B- Waveform polarity and polarity convention of the amplifier inputs If an amplifier is rated as having 120dB common mode rejection ratio, which of the following ratios of in-phase to out-of-phase signals would be expected? A- 10,000: B- 1,000,000: C- 500,000: D- 100,000:1 - answer B- 1,000,000:
Which of the following opposes any change in current? A- Inductance B- Resistance C- Capacitance D- Impedance - answer A- Inductance According to the ACNS guidelines, system bandpass settings for monitoring facial nerve spontaneous muscle activityshould be A- 10‐30 to 16,000 Hz B- 100‐200 to 1000‐3000 Hz C- 1‐250 to 1500 Hz D- 10‐30 to 2500‐3000 Hz - answer A- 10‐30 to 16,000 Hz The unit for Impedance is: A- Farads B- Amperes C- Ohms D- Coulombs - answer C- Ohms Artifact rejection: A- Excludes trials with artifacts exceeding set amplitude values B- Substitutes for common mode rejection C- Eliminates all artifacts regardless of amplitude D- Is needed only for intraoperative recordings - answer A- Excludes trials with artifacts exceeding set amplitude values If you need 100 trials to get a SNR of 2:1, how many trials are needed for a SNR of 20:1? A- 20,
D- Setting the timebase to at least 100 mS - answer B- Sampling at least the Nyquist frequency Which will enhance the analog to digital conversion? A- Use the shortest possible stimulus interval B- Make sure the sampling rate is at least half the signal frequency C- Use the longest timebase possible D- Ensure that the range is appropriate to the size of the signal being recorded - answer D- Ensure that the range is appropriate to the size of the signal being recorded You want to have matching impedances so that: A- You can maximize your common mode rejection B- Horizontal resolution will be optimized C- Vertical resolution will be optimized D- You can minimize your common mode rejection - answer A- You can maximize your common mode rejection If you have a pre-stimulus "negative" delay of 15 mS and a timebase of 45 mS, 15 mS will be displayed: A- Before the stimulus and 45 mS after B- After the stimulus and 30 mS after C- After the stimulus and 45 after D- Before the stimulus and 30 mS after - answer D- Before the stimulus and 30 mS after What should you do in order to optimize vertical resolution? A- Increase number of sampling points B- Ensure that the peak-peak amplitude is 10% of the range of the A-D converter
C- Use an 8 bit instead of a 12-bit converter D- Ensure that the peak-peak amplitude is maximal within the range of the A-D converter - answer B- Ensure that the peak-peak amplitude is 10% of the range of the A-D converter What should you do in order to maximize horizontal resolution? A- Decrease analysis time B- Increase timebase C- Decrease number of data points collected D- Increase number of bits - answer A- Decrease analysis time A constant current stimulator A- Varies the output voltage in order to maintain a certain current level B- Maintains a current level of 5 mA C- Maintains a constant voltage of 250 volts D- Varies the current level in order to maintain a certain voltage level - answer A- Varies the output voltage in order to maintain a certain current level In a somatosensory EP, how will changing the high frequency filter from 30 kHz to 1KHz affect the cortical responses A- Cause a phase lag and appear to prolong the latency B- Increase the amplitude of the responses C- Decrease the amplitude of the responses D- Cause a phase lead and appear to shorten the latency - answer A- Cause a phase lag and appear to prolong the latency What is the required CMRR for an evoked potential system? A- 80 dB
