CNIM - Instrumentation Practice Exam Solution Correct Answers.

A unit of resistance is symbolized by... Ohms Fast Fourier transformation The mathematical transformation f a complex waveform into simpler, more uniform waves The capacity to resolve amplitudes of 256 discrete steps would require an 8 bit A to D converter. This can be represented by... 2^8 What is the minimum required bandpass for an EP system? 0.1 - 5,000 Hz The gain of an amplifier, set to give an output signal of 1 volt for an input signal of 10 uV, is... Gain=output/input Gain=1,000,000 uV/10 uV Gain=100,000 A 100 mS epoch is recorded with a 10 ms post-stimulus triggering. What best describes the resulting sweep? A 100 ms sweep starting 10 ms after the stimulus. SSEP recordings typically require a bandpass of... 30 Hz to 3000 Hz To accurately represent the amplitude of an EP waveform, a match must be made between the... Signal size and the vertical capacity of the digitizer In selecting the horizontal parameters of analysis, the... Sampling rate should be at least two times greater than the highest frequency of in the signal. The assumption that reponses of excessive amplitude are likely to contain artifact forms the basis for... Artifact rejection In a differential amplifier used for IONM, the common mode rejection of in phase signals is typically... 10000 to 1 A differential amplifier records... The difference between the two inputs. An erroneous representation of an analog wave by A to D conversion suggesting a lower frequency due to a low sampling rate is called... Aliasing What are good insulating materials? Glass and Rubber Electrode impedance is defined as opposition to... Alternating current flow Dwell time can be defined as... The intersample interval If not specified, most reports on ABR are displayed... Vertex positive up The horizontal resolution of an evoked potential system... Should be 20 ms per data point or less The difference between the voltages in input 1 and input 2 will make the display of the amplifier... Either up or down In theory, amplitude of the EPs relative to the background noise... Will improve by a factor approximately equal to the square root of the number of epochs averaged. Nyquist frequency... Minimum sampling rate to prevent aliasing Cathode Negative pole or block dot on the bar electrode Aliasing is the result of... Sampling below the Nyquist frequency Changing the low cut BAEP from 100 to 200 Hz will result in... Decreased response latency If the cutoff frequency of a filter is 100 Hz, then a 100 Hz signal will be reduced in amplitude by... 30% If the highest frequency component of an EP is 400 Hz, then the minimum sampling rate required to accurately represent the signal is... 800 Hz Vertical resolution depends on... Number of bits If a 10 uV signal inside 50 uV of noise is averaged for 100 traces. The final signal to noise ration will be... SNR = signal/noise SNR WAS: 1:5 Square root of 100 = 10, so S/N = 10:5 or 2:1 An EP recording system should allow averaging of... At least 4000 trials The input impedance of a differential amplifier must be at least... 100 megaohms When using constant voltage for racial nerve stim and the nerve becomes bathed in CSF, what will occur after the area is suctioned... The current flow will very in order to maintain the preset voltage level Reduction of the high frequency filter... Increases EP latency The sensitivity setting on an amplifier set to produce a vertical deflection of 1 cm with an input of 10 mV is... I cm = 10 mm 1 mV/mm Prestimulus Triggering... Includes a period of recording before the stimulus Given an electrical circuit with a resistance of 1000 ohms and a voltage of 10 volts, the current flow will be... V = IR I = V/R I = 10 V/ 1000 ohms = 0.01 A If you have a signal to noise ratio of 1:2, averaging 64 responses will... Square root of 64 = 8 8:2 = 4:1 Capacitors are electronic devices used to... Store electrical energy With a sampling rate of 10 kHz, the shortest sign wave resolved would be... 0.2 msec? Hz = revolution/sec The phenomenon called "aliasing" Refers to an erroneous representation of an analog signal by digital values Signal-to-noise ratio relates to what? 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? Increase your averages If you have a 5 uV signal amplitude and a 20 uV noise amplitude, how many averages would you need to get a signal to noise ratio of 2:1? SNRi = 1:4 Noise needs to be 8 to be 2:1 Averages = 64 During electrocautery we should... Pause recording The gain of a differential amplifier is defined as... Output voltage divided by input voltage The positive input of a differential amplifier is also called the... Non-inverting input If you get artifact in your subcortical channel you... Use a spare Cs5 electrode The minimum required Common Mode Rejection Ratio of a differential amplifier is... 10,000:1 A differential amplifier with a gain of 1,000,000 has a 0.2 uV signal at its positive input and a 0.8 uV signal at its negative input. The output will be... A downward peak of 0.6 V A 10 Hz signal passing through a 10 Hz locut filters will be: Reduced in amplitude by approximately 30% A major advantage of digital filters over analog filters is... They impose no phase effects on the recorded signal Lowering the SSEP hi-cut filter from 500 Hz to 200 Hz may cause cortical peaks to appear... Longer in latency What time constant would be most effective for cutting out low frequency noise from your signal? 10 ms What is the required horizontal resolution of an EP system? 20 uS per data point or less The vertical resolution of an EP system depends primarily on,,, The number of bits in the A/D converter A 10 bit A/D converter has how many discrete voltage values in its range