BME 732 - Recording Setups and Data Acquisition Basics

medicineman's version from 2015-10-06 00:27

Setup and Acquisition

Question Answer
Data acquisition requirements Aim is to interface the animal/human with the computer. Adapters and suitable cables, preamplifiers, DSP for ADC, software for acquiring data, computer with large RAM and disk storage, and time synchronizers
What is a signal?Signals are physicochemical phenomena that convey information. Can be continuous or discrete and deterministic or random
Basic amplifier requirements The amplifier should not influence the physiological process to be monitored, the measured signal should not be distorted, the amplifier should provide the best possible separation of signal and interference, the amplifier should protect the patient from any hazard or shock, and the amplifier should be protected against any damage due to high input voltages
The input signal consists of 5 components Desired biopotential, undesired biopotentials, power line interference, interference signals generated by the tissue-electrode interface, and noise
Isolation amplifierServes the galvanic decoupling of the patient from the measuring equipment to provide safety from electrical hazards
Block diagram of a digital signal processor Input signal > ADC > Signal processing > DAC > Output signal
NoiseNoise amplitude can be calculated as the square root of the time-averaged RMS of the amplitude of the signal. Noise can be eliminated by filtering, averaging, and following proper methods of signal measurement
FilterA filter is a frequency-selective device that passes signals in one band of frequencies and rejects signals in other bands. Performed to enhance the SNR
FIR filters Usually for discrete signals. Linear. Non-recursive (only dependent on input, not previous outputs)
IIR FiltersNon-linear, recursive (dependent on previous outputs), and can achieve roll-off with fewer filter coefficients than FIR filters
Differential vs single-ended measurement systemsDifferential is generally preferred because it rejects ground loop induced errors and the noise picked up in the environment to a degree. Single-ended systems offer twice as many measurement channels, but are only justified if the induced error is less than the required accuracy of the data
Requirements for using single-ended systems Signal cabling is short and properly shielded or passes through a noise-free environment. All input systems can share a common reference signal at the source. If these criteria cannot be met, a differential system should be used

Frequency Ranges of Common Biopotentials

Question Answer
EOG (electrooculography)0.1 - 10Hz
EEG (electroencephalography)0.1 - 100Hz
ECG (electrocardiogram)0.1 - 600Hz
EMG (electromyography)60 - 1500Hz
AAP (axon action potential)1000 - 10,000Hz

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