Electricity and Transducers Flashcards
Less than 1 mA
Threshold of perception. Fainting tingling sensation
1-8 mA for 1 second
Maximum harmless current intensity. Not painful!
10-20 mA for 1 second
Painful shock with loss of muscular control. “Let go” threshold
20-50 mA for 1 second
Extreme pain, possible fainting, exhaustion, mechanical injury.
Respiratory and heart functions continue. Cannot let go
100-200 mA for 1 second
Ventricular fibrillation will start but the respiratory center may remain intact. Here damage begins to occur. Loss of consciousness
200+ mA for 1 second
Cardiac arrest, severe burns, possible death
10-100 microA
Ventricular fibrillation —> death
Biometrics
Science that includes measurement of physiological variables and parameters
Physiological measurements
Can be obtained passively, applying energy, or reflection/refraction of light
Sensitivity
How small a variation of the parameters can be reliably measured
Range
All levels of input amplitude and frequency over which a device is expected to operate
Operating range
Provides a usable reading from the smallest expected value being measured to the largest expected variable
Linearity
The degree to which variations in the output of an instrument follow variation in input
Frequency response
Variation in frequency over the frequency range of the measurement
Accuracy
Measure of system error (true-measured)
Precision
Degree of reproducibility of a measurement
Hysteresis
A given value of the measured variable result in a different reading when reached in an ascending direction than that which is reached from a descending direction
Stability
Ability of a system to resume a steady-state condition following a disturbance at the input rather than be driven into uncontrolled oscillation
Isolation
To avoid interference between different instruments used simultaneously
Simplicity
Reduction of change of component or human error (i.e. Calibration, zeroing)
Transducer
Converts non-electrical physical parameter (pressure, temperature) to an analogous electrical signal by using a strain gauge and Wheatstone bridge configuration
Strain gauge
A device used to detect mechanical displacement
Wheatstone bridge
An electrical circuit used to measure unknown electrical resistance
Electrodes
Device that captures biological potentials and converts it to an electrical signal
