Sensors Flashcards
it detects the magnitude of a physical parameter and changes it into a signal that can be processed by the system
sensor
an active element of a sensor that is responsible for converting energy from one form to another
transducer
type of transducer that coverts physical quantities into mechanical
mechanical transducer
type of transducer that coverts physical quantities into electrical
electrical transducer
what are the two types of transducer?
mechanical and electrical transducer
these sensors require an external power source to operate
active sensors
these sensors generate an electric current in response to an external stimulus without the need of additional energy source
passive sensors
it detects the temperature of its surroundings and transforms the data into electronic output
temperature sensor
Two dissimilar metals in contact form a thermoelectric junction that produces a voltage proportional
thermocouple
why does thermoelectric junctions occur in pairs?
Because an electrical circuit must form a closed loop
it is a metallic wire wound around a ceramic or glass core and hermetically sealed.
resistance temperature detector/ device (RTD)
it is a semiconductor device, available
in probes of different shapes and sizes, whose
resistance changes exponentially with temperature.
thermistors
what are the two types of thermistor?
negative temperature coefficients (NTC) and positive temperature coefficients (PTC)
this thermistor’s resistance decreases as its temperature increases. it is also commonly used for temperature measurement.
NTC thermistors
this thermistor’s resistance increases as its temperature increases and is primarily used for circuit protection.
PTC thermistors
In this temperature-sensor the forward ac voltage change or the forward ac current change at the pn junction diode due to the temperature change is measured for a constant amplitude of superimposed ac small signal of current δI or voltage δV, respectively, on the constant forward dc current I0
p-n junction temperature sensor
are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade)
temperature.
LM35 temperature sensor
It is composed of two or more metal layers having different coefficients of thermal expansion.
bimetallic strip
in a bimetallic strip, the layers are permanently bonded together. will its structure deform when the temperature changes? (yes or no)
yes
__________ are those sensors that detect electromagnetic radiation in what is generally understood as the broad optical range—from far Infrared to Ultraviolet.
optical sensors
this type of optical sensor is a resistor whose resistance depends on the intensity of light.
light dependent resistor
LDR
photoresistor
this resistor’s resistance is very high but dramatically drops when exposed to light
light dependent resistor
LDR
photoresistor
this is a light-sensitive transistor. one of its types is a photobipolar.
phototransistor
it is a device that converts motion into a sequence of digital pulses. By counting a single bit or decoding a set of bits, the pulses can be converted to relative or absolute position measurements.
optical encoder
emits a light beam (visible or infrared) from its light-emitting element.
photoelectric sensor
a type of photoelectric sensor that is used to detect the light beam reflected from the target
reflective type photoelectric sensor
a type of photoelectric sensor that is used to measure the change in light quantity caused by the target crossing the optical axis.
thrubeam type sensor
a type of photoelectric sensor that light from the emitting element hits the reflector and returns to the light receiving element. When a target is present, the light is interrupted.
retroreflective type sensor
it is a non-contact sensor that detects the presence of an object (often referred to as the “target”) when the target enters the sensor’s field.
proximity sensor
detection of metallic objects (type of proximity sensor)
inductive sensors
Detection of metallic and non-metallic objects (Liquids, plastics, woods). (type of proximity sensor)
capacitive sensors
a type of proximity sensor that use light sensitive elements to detect objects.
photoelectric sensors
a type of proximity sensor that detects the presence of permanent magnets
magnetic sensors
consist of two flat ferromagnetic reeds sealed in an inert atmosphere within a glass capsule.
reed switch
A special kind of variable resistor, whose electrical resistance depends on the external
magnetic force applied
magneto resistor
it is a transducer used for measuring linear displacement. It consists of primary and secondary windings and a movable iron core. It functions much like a transformer, where
voltages are induced in the secondary coil in
response to excitation in the primary coil.
linear variable differential transformer/transducer
The simplest kind of displacement sensor is
a mechanical switch which returns one bit of
information: touching or not touching.
mechanical switch
these are devices that are activated
by an external magnetic field. The output signal from it is the function of magnetic field
density around the device.
hall effect sensor
The most common transducer for
experimentally measuring strain in a
mechanical component is the bonded metal foil strain gage
strain gauge/strain gage
what are the 3 types of strain gage assembly?
uniaxial
biaxial
strain gage rosette
devices that measure acceleration, which is the rate of change of the velocity of an object.
accelerometer
Some materials (such as natural quartz crystal, silicon dioxide, barrium titanite, lead zirconate titanate (PZT)), called piezo crystals, produce a charge in response to a force (or deformation) applied to them.
piezoelectric accelerometer
A _________ can be built by using a permanent magnet as a mass on a spring or cantilever beam and sense the field of the permanent
magnet using a Hall element or magnetoresistive sensor
magnetic accelerometers
it is a sensor or a transducer that converts a load or force acting on it into an electronic signal. This electronic signal can be a voltage change, current change or frequency change depending on the type of load cell and circuitry used
load cell
a process technology used to create tiny
integrated devices or systems that combine
mechanical and electrical components.
micro-electromechanical systems (MEMS)
have the ability to sense, control and actuate on the micro scale, and generate effects on the macro scale.
MEMS
One of the simplest and least expensive ways to measure rotational or linear motion.
potentiometer
made of a pyroelectric sensor (which you can see above as the round metal can with a rectangular crystal in the center), which can
detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted
PIR sensor
sends out a high-frequency sound pulse and then times how long it takes for the echo of the sound to reflect back. The sensor has 2 openings on its front. One opening transmits ultrasonic waves, (like a tiny speaker), the other receives them, (like a tiny microphone)
ultrasonic distance sensor
The effect by which a thermoelectric junction of dissimilar metals produces a voltage relative to temperature
seebeck effect
