BME 101-Quiz 2

Circuits; Bioinstrumentation

sensor (general)

special electronic devices that can transduce biomedical signals into easily measurable electric signals; takes in signals from the body, and amplifies them so engineers and doctors can study them; converts the input parameter into a signal (usually an electrical voltage)

processor

modifies the input parameter after it is sensed by a sensor

examples of a processor/processing

* amplification of the signal


* filtering to remove unwanted information
* comparison to signals from previous measurements/control signals

examples of a sensor

* thermometers
* brain scans
* electrocardiograms

input

parameter of interest measured in a typical system

output

the reading that the user can comprehend that a typical system creates

types of input

* temperature
* O2 saturation
* blood pressure
* electrical potentials
* pH
* glucose concentration

receiver

a device that presents an interpretable message to humans; often a digital readout or a computer display

measurand

the physical quantity, property, or condition that is to be measured/monitored

measurand examples

* biopotential
* pressure flow
* temperature
* impedance
* chemical concentration
* dimension
* imaging

sensor (specific)

a device that transforms the measurand to an electrical signal without loading the source (ex. not interfering with the process)

actuator

a device that transforms the electrical energy into a mechanical energy (ex. motor)

transducer

a device that transforms one form of energy into the other form (ex. loud speaker)

voltage (V)

the electromotive force needed to produce the flow of electrons; the force that pushes the flow of charge

current (i)

the rate of flow of electrical charge

ohm’s law defined

the potential difference (voltage drop (V)) across an ideal conductor is proportional to the current (i) that flows through it, and the resistance (R) of the conductor is the constant of proportionality

ohm’s law equation

V = iR

when temperature is high…

…resistance is high

when temperature is low…

…resistance is low

resistance increases with…

increasing length and decreasing area

why do we need resistors?

* limit current flow (mostly)
* divide voltages (sometimes)

conductor

freely passes electric current

semiconductor

has electrical properties between conductor and insulator

insulator

does not pass electrical current

passive electronic components

* do not require an external energy source
* stores energy
* resistors, capacitors, inductors

active electronic components

* requires an external energy source
* fundamental properties vary with input
* diodes, transistors, integrated circuits

capacitor

stores energy in an electric field between parallel plates

inductor

stores energy in a magnetic field

branch

* represents a single element such as a voltage source/resistor


* represents any 2-terminal element

node

the point of connection between 2 or more branches

loop

any closed path in a circuit

mesh

a type of loop that fills an open space

kirchoff’s voltage law

* the sum of potential voltage drops around a loop is zero
* the sum of currents a junction are zero--currents at a junction are conserved

thermocouple

* formed by fusing 2 dissimilar metals to produce 2 junctions
* heterogenous combinations of different metals
* one of the most commonly used temperature-sensing elements

thermistor

* an electrical resistor whose resistance is greatly reduced by heating
* homogenous composites of dissimilar metals that form thermally sensitive resistive

strain gauge

an instrument that measures strain

stress

when a material is loaded with a force it produces a stress that causes a material to deform

strain

the amount of deformation in the direction of the applied force divided by the initial length of the material

optical sensor

convert light into an electronic signal

analog sensors

produce continuous signals that are related to the sensed parameter

digital sensors

produce digital outputs (ex. high/low voltage or current--ON/OFF)

passive sensor

measures energy from outside source

active sensor

emits energy and measures the environmental effects on that energy

resolution

the smallest unit of measurement that can be indicated by an instrument

sensitivity

the smallest amount of difference in quantity that will change an instrument’s reading