2. Sensors::
A sensor (also called detector) is a converter that measures a physical quantity
and converts it into a signal which can be read by an observer or by an (today mostly
electronic) instrument. For example, a mercury-in-glass thermometer converts the
measured temperature into expansion and contraction of a liquid which can be read on
a calibrated glass tube. A thermocouple converts temperature to an output voltage
which can be read by a voltmeter. For accuracy, most sensors are calibrated against
known standards.
Sensors are used in everyday objects such as touch-sensitive elevator buttons
(tactile sensor) and lamps which dim or brighten by touching the base. There are also
innumerable applications for sensors of which most people are never aware.
Applications include cars, machines, aerospace, medicine, manufacturing and
robotics.
A sensor is a device which receives and responds to a signal when touched. A
sensor's sensitivity indicates how much the sensor's output changes when the
measured quantity changes. For instance, if the mercury in a thermometer moves 1 cm
when the temperature changes by 1 °C, the sensitivity is 1 cm/°C (it is basically the
slope Dy/Dx assuming a linear characteristic). Sensors that measure very small
changes must have very high sensitivities. Sensors also have an impact on what they
measure; for instance, a room temperature thermometer inserted into a hot cup of
liquid cools the liquid while the liquid heats the thermometer. Sensors need to be
designed to have a small effect on what is measured; making the sensor smaller often
improves this and may introduce other advantages. Technological progress allows
more and more sensors to be manufactured on a microscopic scale as microsensors
using MEMS technology. In most cases, a microsensor reaches a significantly higher
speed and sensitivity compared with macroscopic approaches.
3. Classification of measurement errors
Sensor Principles:
A good sensor obeys the following rules:
Is sensitive to the measured property only
Is insensitive to any other property likely to be encountered in its application
Does not influence the measured property
Ideal sensors are designed to be linear or linear to some simple mathematical function
of the measurement, typically logarithmic. The output signal of such a sensor is
linearly proportional to the value or simple function of the measured property. The
sensitivity is then defined as the ratio between output signal and measured property.
For example, if a sensor measures temperature and has a voltage output, the sensitivity
is a constant with the unit [V/K]; this sensor is linear because the ratio is constant at
all points of measurement.
Resolution:
The resolution of a sensor is the smallest change it can detect in the quantity that it is
measuring. Often in a digital display, the least significant digit will fluctuate,
indicating that changes of that magnitude are only just resolved. The resolution is
related to the precision with which the measurement is made. For example, a scanning
tunneling probe (a fine tip near a surface collects an electron tunneling current) can
resolve atoms and molecules.
4. Sensor deviations
If the sensor is not ideal, several types of deviations can be observed:
The sensitivity may in practice differ from the value specified. This is called a
sensitivity error, but the sensor is still linear.
Since the range of the output signal is always limited, the output signal will
eventually reach a minimum or maximum when the measured property exceeds
the limits. The full scale range defines the maximum and minimum values of
the measured property.
If the output signal is not zero when the measured property is zero, the sensor
has an offset or bias. This is defined as the output of the sensor at zero input.
If the sensitivity is not constant over the range of the sensor, this is called non
linearity. Usually this is defined by the amount the output differs from ideal
behavior over the full range of the sensor, often noted as a percentage of the
full range.
If the deviation is caused by a rapid change of the measured property over time,
there is a dynamic error. Often, this behavior is described with a bode plot
showing sensitivity error and phase shift as function of the frequency of a
periodic input signal.
If the output signal slowly changes independent of the measured property, this
is defined as drift (telecommunication).
Long term drift usually indicates a slow degradation of sensor properties over a
long period of time.
Noise is a random deviation of the signal that varies in time.
Hysteresis is an error caused by when the measured property reverses direction,
but there is some finite lag in time for the sensor to respond, creating a different
offset error in one direction than in the other.
If the sensor has a digital output, the output is essentially an approximation of
the measured property. The approximation error is also called digitization error.
If the signal is monitored digitally, limitation of the sampling frequency also
can cause a dynamic error, or if the variable or added noise changes
periodically at a frequency near a multiple of the sampling rate may induce
aliasing errors.
The sensor may to some extent be sensitive to properties other than the
property being measured. For example, most sensors are influenced by the
temperature of their environment.
5. List of sensors::
1)Acoustic, sound, vibration:
Geophone
Hydrophone
Lace Sensor a guitar pickup
Microphone
Seismometer
2)Automotive, transportation:
Air-fuel ratio meter
Blind spot monitor
Crankshaft position sensor
Curb feeler, used to warn driver of curbs
Defect detector, used on railroads to detect axle and signal problems in passing
trains
Engine coolant temperature sensor, or ECT sensor, used to measure the engine
temperature
Hall effect sensor, used to time the speed of wheels and shafts
MAP sensor, Manifold Absolute Pressure, used in regulating fuel metering.
Mass flow sensor, or mass airflow (MAF) sensor, used to tell the ECU the mass
of air entering the engine
Oxygen sensor, used to monitor the amount of oxygen in the exhaust
Parking sensors, used to alert the driver of unseen obstacles during parking
manoeuvres
Radar gun, used to detect the speed of other objects
Speedometer, used measure the instantaneous speed of a land vehicle
Speed sensor, used to detect the speed of an object
Throttle position sensor, used to monitor the position of the throttle in an
internal combustion engine
Tire-pressure monitoring sensor, used to monitor the air pressure inside the
tires
Torque sensor, or torque transducer or torquemeter measures torque (twisting
force) on a rotating system.
Transmission fluid temperature sensor, used to measure the temperature of the
transmission fluid
Turbine speed sensor (TSS), or input speed sensor (ISS), used to measure the
rotational speed of the input shaft or torque converter
Variable reluctance sensor, used to measure position and speed of moving
metal components
Vehicle speed sensor (VSS), used to measure the speed of the vehicle
Water sensor or water-in-fuel sensor, used to indicate the presence of water in
fuel
6. Wheel speed sensor, used for reading the speed of a vehicle's wheel rotation
3)Chemical
Breathalyzer
Carbon dioxide sensor
Carbon monoxide detector
Catalytic bead sensor
Chemical field-effect transistor
Electrochemical gas sensor
Electronic nose
Electrolyte–insulator–semiconductor sensor
Fluorescent chloride sensors
Holographic sensor
Hydrocarbon dew point analyzer
Hydrogen sensor
Hydrogen sulfide sensor
Infrared point sensor
Ion-selective electrode
Nondispersive infrared sensor
Microwave chemistry sensor
Nitrogen oxide sensor
Olfactometer
Optode
Oxygen sensor
Pellistor
pH glass electrode
Potentiometric sensor
Redox electrode
Smoke detector
Zinc oxide nanorod sensor
4)Electric current, electric potential, magnetic, radio:
Current sensor
Electroscope
Galvanometer
Hall effect sensor
Hall probe
Magnetic anomaly detector
Magnetometer
MEMS magnetic field sensor
Metal detector
Planar Hall sensor
Radio direction finder
Voltage detector
7. 5)Environment, weather, moisture, humidity:
Actinometer
Bedwetting alarm
Ceilometer
Dew warning
Electrochemical gas sensor
Fish counter
Frequency domain sensor
Gas detector
Hook gauge evaporimeter
Humistor
Hygrometer
Leaf sensor
Pyranometer
Pyrgeometer
Psychrometer
Rain gauge
Rain sensor
Seismometers
SNOTEL
Snow gauge
Soil moisture sensor
Stream gauge
Tide gauge
6)Flow, fluid velocity:
Air flow meter
Anemometer
Flow sensor
Gas meter
Mass flow sensor
Water meter
7)Ionising radiation, subatomic particles:
Bubble chamber
Cloud chamber
Geiger counter
Neutron detection
Particle detector
Scintillation counter
Scintillator
Wire chamber
12. Sensor grid
Sensor node
Soft sensor
SONAR
Staring array
Transducer
Ultrasonic sensor
Video sensor
Visual sensor network
Wheatstone bridge
Wireless sensor network
Other sensors and sensor related properties and concepts
Actigraphy
Analog image processing
Atomic force microscopy
Atomic Gravitational Wave Interferometric Sensor
Attitude control (spacecraft), Horizon sensor, Earth sensor, Sun sensor
Catadioptric sensor
Chemoreceptor
Compressive sensing
Cryogenic particle detectors
Dew warning
Diffusion tensor imaging
Digital holography
Electronic tongue
Fine Guidance Sensor
Flat panel detector
Functional magnetic resonance imaging
Glass break detector
Heartbeat sensor
Hyperspectral sensors
IRIS (Biosensor), Interferometric Reflectance Imaging Sensor
Laser beam profiler
Littoral Airborne Sensor/Hyperspectral
LORROS
Millimeter wave scanner
Magnetic resonance imaging
Moire deflectometry
Molecular sensor
Nanosensor
Nano-tetherball Sensor
Omnidirectional camera
Optical coherence tomography
Phase unwrapping techniques
13. Positron emission tomography
Push broom scanner
sensitive air-conductivity sensors
Quantization (signal processing)
Range imaging
Scanning SQUID microscope
Single-Photon Emission Computed Tomography (SPECT)
Smartdust
SQUID, Superconducting quantum interference device
SSIES, Special Sensors-Ions, Electrons, and Scintillation thermal plasma
analysis package
SSMIS, Special Sensor Microwave Imager / Sounder
Structured-light 3D scanner
Sun sensor, Attitude control (spacecraft)
Superconducting nanowire single-photon detector
Thin-film thickness monitor
Time-of-flight camera
TriDAR, Triangulation and LIDAR Automated Rendezvous and Docking
Unattended Ground Sensors
14. Examples of each type of Sensors:
Acoustic, sound, vibration:
a)Hydrophone:
A hydrophone (Greek "hydro" = "water" and "phone" = "sound") is a
microphone designed to be used underwater for recording or listening to
underwater sound. Most hydrophones are based on a piezoelectric transducer
that generates electricity when subjected to a pressure change. Such
piezoelectric materials, or transducers can convert a sound signal into an
electrical signal since sound is a pressure wave. Some transducers can also
serve as a projector, but not all have this capability, and may be destroyed if
used in such a manner.
A hydrophone can "listen" to sound in air, but will be less sensitive due to its
design as having a good acoustic impedance match to water, which is a denser
fluid than air. Likewise, a microphone can be buried in the ground, or
immersed in water if it is put in a waterproof container, but will give similarly
poor performance due to the similarly bad acoustic impedance match.
15. Automotive, transportation:
a) Air–fuel ratio meter
An air–fuel ratio meter monitors the air–fuel ratio of an internal combustion
engine. Also called air–fuel ratio gauge, air–fuel meter, or air–fuel gauge. It reads
the voltage output of an oxygen sensor, sometimes also called lambda sensor, whether
it be from a narrow band or wide band oxygen sensor.
The original narrow-band oxygen sensors became factory installed standard in
the late 1970s and early 80s. In recent years, a newer and much more accurate wide-
band sensor, though more expensive, has become available.
Most stand-alone narrow-band meters have 10 LEDs and some have more.
Also common, narrow band meters in round housings with the standard mounting 2
1/16" and 2 5/8" diameters, as other types of car 'gauges'. These usually have 10 or 20
LEDs. Analogue 'needle' style gauges are also available.
As stated above, there are wide-band meters that stand alone or are mounted in
housings. Nearly all of these show the air–fuel ratio on a numeric display, since the
wide-band sensors provide a much more accurate reading. And since they use more
accurate electronics, these meters are more expensive.
16. b)Curb feelers
Curb feelers or curb finders are springs or wires installed on a vehicle
which act as "whiskers" to warn drivers that they are too close to the curb or other
obstruction.
The devices are fitted low on the body, close to the wheels. As the vehicle
approaches the curb, the protruding 'feelers' act as whiskers and scrape against the
curb, making a noise and alerting the driver in time to avoid damaging the wheels or
hubcaps. The feelers are manufactured to be flexible and do not easily break.
Chemical:
Electrochemical gas sensor
The sensors contain two or three electrodes, occasionally four, in contact with an
electrolyte. The gas diffuses into the sensor, through the back of the porous membrane
to the working electrode where it is oxidized or reduced. This electrochemical reaction
results in an electric current that passes through the external circuit. In addition to
measuring, amplifying and performing other signal processing functions, the external
circuit maintains the voltage across the sensor between the working and counter
electrodes for a two electrode sensor or between the working and reference electrodes
for a three electrode cell. At the counter electrode an equal and opposite reaction
17. occurs, such that if the working electrode is an oxidation, then the counter electrode is
a reduction.
Hydrocarbon dew point
The hydrocarbon dew point is the temperature (at a given pressure) at which the
hydrocarbon components of any hydrocarbon-rich gas mixture, such as natural gas,
will start to condense out of the gaseous phase. It is often also referred to as the HDP
or the HCDP. The maximum temperature at which such condensation takes place is
called the cricondentherm.[1] The hydrocarbon dew point is a function of the gas
composition as well as the pressure.
The hydrocarbon dew point is universally used in the natural gas industry as an
important quality parameter, stipulated in contractual specifications and enforced
throughout the natural gas supply chain, from producers through processing,
transmission and distribution companies to final end users.
The hydrocarbon dew point of a gas is a different concept from the water dew point,
the latter being the temperature (at a given pressure) at which water vapor present in a
gas mixture will condense out of the gas.
In the United States, the hydrocarbon dew point of processed, pipelined natural gas is
related to and characterized by the term GPM which is the gallons of liquifiable
hydrocarbons contained in 1,000 cubic feet (28 m3) of natural gas at a stated
temperature and pressure. When the liquifiable hydrocarbons are characterized as
being hexane or higher molecular weight components, they are reported as GPM
(C6+).[2][3]
However, the quality of raw produced natural gas is also often characterized by the
term GPM meaning the gallons of liquifiable hydrocarbons contained in 1,000 cubic
feet (28 m3) of the raw natural gas. In such cases, when the liquifiable hydrocarbons in
the raw natural gas are characterized as being ethane or higher molecular weight
components, they are reported as GPM (C2+). Similarly, when characterized as being
propane or higher molecular weight components, they are reported as GPM (C3+).[4]
Care must be taken not to confuse the two different definitions of the term GPM.
18. Although GPM is an additional parameter of some value, most pipeline
operators and others who process, transport, distribute or use natural gas are primarily
interested in the actual HCDP, rather than GPM. Furthermore, GPM and HCDP are
not interchangeable and one should be careful not to confuse what each one exactly
means.
Electric current, electric potential, magnetic, radio
a)Magnetic anomaly detector
A magnetic anomaly detector (MAD) is an instrument used to detect minute
variations in the Earth's magnetic field. The term refers specifically to magnetometers
used by military forces to detect submarines (a mass of ferromagnetic material creates
a detectable disturbance in the magnetic field); the military MAD gear is a descendent
of geomagnetic survey instruments used to search for minerals by the disturbance of
the normal earth-field.
To reduce interference from electrical equipment or metal in the fuselage of
the aircraft, the MAD sensor is placed at the end of a boom or a towed aerodynamic
device. Even so, the submarine must be very near the aircraft's position and close to
the sea surface for detection of the change or anomaly. The size of the submarine and
its hull composition determine the detection range. MAD devices are usually mounted
on aircraft.
19. There is some misunderstanding of the mechanism of detection of submarines in
water using the MAD boom system. Magnetic moment displacement is ostensibly the
main disturbance, yet submarines are detectable even when oriented parallel to the
Earth's magnetic field, despite construction with non-ferromagnetic hulls. For
example, the Soviet-Russian Alfa class submarine, whose hull is constructed out of
titanium to give dramatic submerged performance and protection from detection by
MAD sensors, is still detectable
This is due in part to the fact that even submarines with titanium hull will still
have a substantial content of ferromagnetic materials as the nuclear reactor, steam
turbines, auxiliary diesel engines and numerous other systems will be manufactured
from steel and nickel alloys.
b)Radio direction finder
A radio direction finder (RDF) is a device for finding the direction to a radio
source. Due to low frequency propagation characteristic to travel very long distances
and "over the horizon", it makes a particularly good navigation system for ships, small
boats, and aircraft that might be some distance from their destination (see Radio
navigation). The distinct technology Range and Direction Finding was the
abbreviation used to describe the predecessor to radar.
In use, the RDF operator would first tune the receiver to the correct
frequency, then manually turn the loop, either listening or watching an S meter to
determine the direction of the null (the direction at which a given signal is weakest) of
a long wave (LW) or medium wave (AM) broadcast beacon or station (listening for
the null is easier than listening for a peak signal, and normally produces a more
accurate result). This null was symmetrical, and thus identified both the correct degree
heading marked on the radio's compass rose as well as its 180-degree opposite. While
this information provided a baseline from the station to the ship or aircraft, the
navigator still needed to know beforehand if he was to the east or west of the station in
order to avoid plotting a course 180-degrees in the wrong direction. By taking
bearings to two or more broadcast stations and plotting the intersecting bearings, the
navigator could locate the relative position of his ship or aircraft. Later, RDF sets were
equipped with rotatable ferrite loopstick antennas, which made the sets more portable
20. and less bulky. Some were later partially automated by means of a motorized antenna
(ADF). A key breakthrough was the introduction of a secondary vertical whip or
'sense' antenna that substantiated the correct bearing and allowed the navigator to
avoid plotting a bearings 180 degrees opposite the actual heading. After World War II,
there many small and large firms making direction finding equipment for mariners,
including Apelco, Aqua Guide, Bendix, Gladding (and its marine division, Pearce-
Simpson), Ray Jefferson, Raytheon, and Sperry. By the 1960s, many of these radios
were actually made by Japanese electronics manufacturers, such as Panasonic, Fuji
Onkyo, and Koden Electronics Co., Ltd. In aircraft equipment, Bendix and Sperry-
Rand were two of the larger manufacturers of RDF radios and navigation instruments.
Environment, weather, moisture, humidity:
Humistor
A humidity sensor has a sensing portion which usually comprises a
humidity-sensitive resistor composed of an organic polymer, such as a polyamide
resin, polyvinyl chloride or polyethylene, or a metal oxide. A capacitive humidity
sensor detects humidity based on a change of capacitance between two detection
electrodes provided on a semiconductor substrate. The capacitance type humidity
sensor detects humidity by measuring the change in the electrostatic capacity of an
element corresponding to the ambient humidity. A resistive humidity sensor detects
relative humidity by measuring the change in the resistance of an element
corresponding to the ambient humidity. Most of the resistance type humidity sensors
include an electrolytic, polymeric, or metallic oxide sensor element. An impedance
humidity sensor changes its electrical impedance as the humidity of the surrounding
environment changes, and the measured impedance is converted into humidity
readings.
A humidity sensor measures the humidity level by measuring the change in
the resistance of an element or the change in the electrostatic capacity of that element
as it absorbs or releases moisture. Humidity sensors can be used not only to measure
21. the humidity in an atmosphere but also to automatically control humidifiers,
dehumidifiers, and air conditioners for humidity adjustment.
Flow, fluid velocity
Mass flow sensor
A mass air flow sensor is used to find out the mass flowrate of air entering a
fuel-injected internal combustion engine. The air mass information is necessary for the
engine control unit (ECU) to balance and deliver the correct fuel mass to the engine.
Air changes its density as it expands and contracts with temperature and pressure. In
automotive applications, air density varies with the ambient temperature, altitude and
the use of forced induction, which means that mass flow sensors are more appropriate
than volumetric flow sensors for determining the quantity of intake air in each piston
stroke.
Ionising radiation, subatomic particles:
Geiger counter
Geiger counter instruments consist of two main elements; the Geiger-Muller
tube, and the processing and display electronics. The radiation sensing element is an
22. inert gas-filled Geiger-Muller tube (usually containing helium, neon or argon with
halogens added) which briefly conducts electrical charge when a particle or photon of
radiation makes the gas conductive by ionization. The tube has the property of being
able to amplify each ionization event by means of the Townsend avalanche effect and
produces an easily measured current pulse which is passed to the processing
electronics.
Navigation instruments
a) Yaw-rate sensor::
A yaw-rate sensor is a gyroscopic device that measures a vehicle’s angular
velocity around its vertical axis. . The angle between the vehicle's heading and vehicle
actual movement direction is called slip angle, which is related to the yaw rate. The
measurement of plane to the earth from the ground my home.
Yaw rate sensors are used in aircraft and in the electronic stability control systems
of cars.
b)A ring laser gyroscope (RLG)::
A ring laser gyroscope (RLG) consists of a ring laser having two counter-
propagating modes over the same path in order to detect rotation. It operates on the
principle of the Sagnac effect which shifts the nulls of the internal standing wave
pattern in response to angular rotation. Interference between the counter-propagating
23. beams, observed externally, reflects shifts in that standing wave pattern, and thus
rotation.
A certain rate of rotation induces a small difference between the time it takes
light to traverse the ring in the two directions according to the Sagnac effect. This
introduces a tiny separation between the frequencies of the counter-propagating
beams, a motion of the standing wave pattern within the ring, and thus a beat pattern
when those two beams are interfered outside the ring. Therefore the net shift of that
interference pattern follows the rotation of the unit in the plane of the ring.
Examples of RLG applications:
Airbus A320[3]
Agni III
ASM-135 US Anti-satellite missile.
Boeing 757-200.
Boeing 777
MK39 Ship's Internal Navigation System used in NATO surface ships and
submarines
P3 Orion
Optical, light, imaging, photon:
Electro-optical sensors:
Electro-optical sensors are electronic detectors that convert light, or a change in
light, into an electronic signal. They are used in many industrial and consumer
applications, for example:
Lamps that turn on automatically in response to darkness
Position sensors that activate when an object interrupts a light beam
Flash detection, to synchronize one photographic flash to another
24. Light-addressable potentiometric sensor:
A light-addressable potentiometric sensor (LAPS) is a sensor that uses light (e.g.
LEDs) to select what will be measured. Light can activate carriers in semiconductors
and example is the pH-sensitive LAPS (range pH4 to pH10) that uses LEDs in
combination with (semi-conducting) silicon and pH-sensitive Ta2O5 (SiO2; Si3N4)
insulator. The LAPS has several advantages over other types of chemical sensors. The
sensor surface is completely flat, no structures, wiring or passivation are required. At
the same time, the "light-addressability" of the LAPS makes it possible to obtain a
spatially resolved map of the distribution of the ion concentration in the specimen.
The spatial resolution of the LAPS is an important factor and is determined by the
beam size and the lateral diffusion of photocarries in the semiconductor substrate. By
illuminating parts of the semiconductor surface, elctron-hole pairs are generated and a
photocurrent flows. The LAPS is a semiconductor based chemical sensor with an
electrolyte-insulator-semiconductor (EIS) structure. Under a fixed bias voltage, the
AC (kHz range) photocurrent signal varies depending of the solution. A two-
dimensional mapping of the surface from the LAPS is possible by using a scanning
laser beam
.
Pressure:
a) Pressure sensor
A pressure sensor measures pressure, typically of gases or liquids. Pressure is an
expression of the force required to stop a fluid from expanding, and is usually stated in
terms of force per unit area. A pressure sensor usually acts as a transducer; it generates
a signal as a function of the pressure imposed.
Pressure sensors are used for control and monitoring in thousands of everyday
applications. Pressure sensors can also be used to indirectly measure other variables
such as fluid/gas flow, speed, water level, and altitude. Pressure sensors can
alternatively be called pressure transducers, pressure transmitters, pressure senders,
pressure indicators and piezometers, manometers, among other names.
25. b) Proximity
A proximity sensor is a sensor able to detect the presence of nearby objects without
any physical contact.
A proximity sensor often emits an electromagnetic field or a beam of electromagnetic
radiation (infrared, for instance), and looks for changes in the field or return signal.
The object being sensed is often referred to as the proximity sensor's target. Different
proximity sensor targets demand different sensors. For example, a capacitive
photoelectric sensor might be suitable for a plastic target; an inductive proximity
sensor always requires a metal target.
The maximum distance that this sensor can detect is defined "nominal range". Some
sensors have adjustments of the nominal range or means to report a graduated
detection distance.
Proximity sensors can have a high reliability and long functional life because of the
absence of mechanical parts and lack of physical contact between sensor and the
sensed object.
Proximity sensors are also used in machine vibration monitoring to measure the
variation in distance between a shaft and its support bearing. This is common in large
steam turbines, compressors, and motors that use sleeve-type bearings.
International Electrotechnical Commission (IEC) 60947-5-2 defines the technical
details of proximity sensors.
A proximity sensor adjusted to a very short range is often used as a touch switch.
26. Applications
Parktronic, car bumpers that sense distance to nearby cars for parking
Ground proximity warning system for aviation safety
Vibration measurements of rotating shafts in machinery [1]
Top dead centre (TDC)/camshaft sensor in reciprocating engines.
Sheet break sensing in paper machine.
Anti-aircraft warfare
Roller coasters
Conveyor systems
Touch screens on mobile devices that come in close proximity with the face
All these deviations can be classified as systematic errors or random errors.
Systematic errors can sometimes be compensated for by means of some kind of
calibration strategy. Noise is a random error that can be reduced by signal processing,
such as filtering, usually at the expense of the dynamic behavior of the sensor.
