N-Instrumentation 4

Front 1

Which term refers to a signal sampling period?

Back 1

An epoch is a signal sampling period. Example: in a 2-second period, the EEG could be sampled 256 times using Fast-Fourier Transform (FFT) analysis.

Front 2

_______ refers to a point on a waveform's 360 degree cycle at an instant in time.

Back 2

Phase refers to a point on a waveform's 360 degree cycle at an instant in time. When the peaks and valleys of two waveforms coincide, they are in phase. When they do not coincide, they are out of phase. The degree to which the two waveforms are out of phase is expressed by phase angle which is measured in degrees.

Front 3

Which method produces the largest signal voltage by transforming both positive and negative halves into an equivalent DC signal?

Back 3

Full-wave rectification produces the largest signal voltage by transforming both positive and negative halves into an equivalent DC signal.

Front 4

Which is the proportion of signal to artifact amplitudes measured in dB?

Back 4

The signal-to-noise ratio is the proportion of signal to artifact amplitudes measured in dB. This value depends on the bandpass selected and should be measured at 60 Hz (since this is frequency of 60-Hz artifact). Example: signal-to-noise ratios should exceed 60 dB (1000:1) to minimize contamination by artifact. This specification should be as high as possible.

Front 5

In _______, EEG signals are rapidly sampled, digitized, and decomposed into a series of waveforms of different frequencies. This technique calculates amplitudes for frequencies within a bandpass to determine the power distribution of a signal.

Back 5

In Fast Fourier Transformation analysis, EEG signals are rapidly sampled, digitized, and decomposed into a series of waveforms of different frequencies. This technique calculates amplitudes for frequencies within a bandpass to determine the power distribution of a signal.

Front 6

_______ occurs when an EMG signal travels to an EEG electrode and contaminates these recordings.

Back 6

Volume conduction occurs when an EMG signal travels to an EEG electrode and contaminates these recordings. Volume conduction is signal movement across the body through the fluid surrounding cells (interstitial fluid).

Front 7

Which integration method results in a voltage that is two times peak voltage?

Back 7

The peak-peak integration method results in a voltage that is two times peak voltage. Voltage is equivalent to the absolute amplitude of an AC signal. This value is calculated as the difference between the largest positive and negative peaks.

Front 8

The _______ is the absolute difference between the high-pass and low-pass frequencies, measured in hertz.

Back 8

The bandwidth is the absolute difference between the high-pass and low-pass frequencies measured in hertz.

Front 9

_______ is the rate of electron movement through a circuit.

Back 9

Current is the rate of electron flow through a conductor measured in amperes. Analogy: the flow of gallons of water per second through an irrigation pipe.

Front 10

Which is the first amplification stage in an instrument that requires several stages to increase a low-level signal to voltage levels required for processing?

Back 10

A preamplifier is the first amplification stage in an instrument that requires several stages to increase a low-level signal to voltage levels required for processing.

Front 11

Which measures the noise due to instrument and environmental sources?

Back 11

A dummy subject measures the noise due to instrument and environmental sources. Resistors may be inserted into the input jack of a biomedical instrument to simulate a typical skin-electrode resistance (10 Kohms) of a human subject. The voltage displayed is a measure of the instrument's sensitivity.

Front 12

Which of these is an interval between two frequencies that represents a 2:1 ratio?

Back 12

An octave is an interval between two frequencies that represents a 2:1 ratio.

Front 13

_______ is the ability of a differential amplifier to subtract signals common to active and reference electrodes.

Back 13

Common mode rejection is the ability of a differential amplifier to subtract signals common to active and reference electrodes. The difference in signal voltage between these electrodes (which is mainly the biological signal of interest) should be multiplied millions of times more than signals that are common to both electrodes (which are mainly artifact).

Front 14

_______ refers to the actual frequencies selected by a filter for further analysis.

Back 14

Bandpass refers to the actual frequencies selected by a filter for further analysis. Bandpass is the range of frequencies passed by a bandpass filter.

Front 15

An amplifier's differential input impedance should be at least _____ times the skin-electrode impedance.

Back 15

An amplifier's differential input impedance should be at least 100 times the skin-electrode impedance. This is necessary to maximize the signal voltage reaching an amplifier. This specification should be as high as possible.

Front 16

A(n) _______ multiplies the voltage of a low-amplitude signal.

Back 16

An amplifier multiplies the voltage of a low-amplitude signal. Example: amplification is used in instruments like an EEG to analyze signals and drive displays.

Front 17

Which of these protects a patient from shock hazard by converting an electrical signal to a beam of light that is projected across a gap and reconverted into an electrical signal?

Back 17

An optical isolator protects a patient from shock hazard by converting an electrical signal to a beam of light that is projected across a gap and reconverted into an electrical signal.

Front 18

Which of these converts a filtered AC signal into a positive DC signal for integration (calculation of a signal voltage)?

Back 18

A rectifier converts a filtered AC signal into a positive DC signal for integration (calculation of a signal voltage).

Front 19

Which is a unit of resistance?

Back 19

An ohm is a unit of resistance to current flow. Example: skin-electrode impedance is measured in Kohms (thousands of ohms).

Front 20

A(n) _______ prevents current flow under normal circumstances.

Back 20

An insulator prevents current flow under normal circumstances. Example: rubber encasing a copper wire prevents shock hazard.