Report on Sensors

REPORT ON SENSORS
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Abstract
Task 0 provides an introduction to the
sensors as a device that detects events and
variations in a physical stimulus and
provides a corresponding signal at the output
that can be recorded and measured. Some of
the basic requirements of a sensor include
linearity, time response, repeatability,
stability, sensitivity, accuracy, and range.
Sensors are classified in terms of stimuli
such as optical, mechanical, thermal,
magnetic, electric, and acoustic. For
operation of a sensor, there is a need for an
active power signal or input signal
requirement, and based on this signal of
excitation, the signal generates output.
1. INTRODUCTION
A sensor can be defined as a subsystem,
module, or a device whose function is to
detect changes in the environment or events
and then convey the information to
computer processors or other electronics. A
sensor converts physical parameter such as
speed, humidity, blood pressure, or
temperature into a signal which can be
electrically determined. An analogue sensor
generates constantly varying signal at the
output over a range of values. Normally, the
output is voltage and this signal at the output
is proportional to the measurand. The
quantity that is being determined such as
strain, pressure, temperature, and speed are
all continuous in nature and therefore they
are analogue quantities [1].
Any device that provides a usable output in
response to any given measurand:
Figure 1: Operation of a sensor [2]
Previously, analogue sensors such as force-
sensing resistors and potentiometers were
widely used and some of them are still being
used currently. Currently, most sensors
convert the measurement of physical
quantities into electrical signals. Sensors are
used in daily objects like tactile sensor used
in touch-sensitive buttons and make the
lamps brighten or dim by touching the base.
The application of sensors has expanded
beyond traditional fields of flow, pressure,
or temperature measurement with the
advancements in microcontroller and
micromachinery platforms. Applications of
these sensors include robotics, medicine,
cars, aerospace, machinery and
manufacturing.
The sensitivity of any sensor shows how
much the output of the sensor varies when
the input quantity being determined changes.
Sensors are normally designed to have a
small impact on what is being determined,
making the sensor smaller normally
improves this may result in some benefits.
Some of the factors that should be
considered when selecting a sensor include
repeatability, cost, resolution, calibration,
range, environmental condition, and
accuracy.
Classification of Sensors
Sensors are categorized according to
application, property, material and
technology, transduction principles, and
primary input measured. In the classification
of sensors according to the application,
sensors can be categorized as motion
detectors, image sensors, biosensors, and
accelerometers. According to energy or
power requirements, sensors can be grouped
as passive sensors such as a photoconductive
cell or active sensor such as radiometers.
Classification of sensors according to the
property include acceleration such as
accelerometers, gas and chemical such as
electrochemical, image such as CMOS,

biosensors such as resonant mirror,
proximity and displacement such as
ultrasonic, flow such as thermal mass,
pressure such as electronic, and temperature
such as thermistors [2].
2. METHODOLOGY
From figure 1 above, the basic components
involved during the operations of a sensor
include the sensor element, the input and
output. The sensor element is a system
possessing a variable number of
components. The other basic components of
a sensor include sensor signal processing
hardware, sensor connections and
packaging, and the sensor element. There
are many technologies available to convert a
magnet signal into an electrical signal.
Figure 2: Components of a sensor
A sensor device measures physical data of
the parameter to be monitored and should
also have specific features such as
sensitivity and accuracy. The continuous
analogue signal generated by the sensors is
digitalized by an analogue-to-digital
converter and then conveyed to controllers
for purposes of processing. Some sensors
have the essential electronics to convert the
input energy form into readings which can
be retrieved through digital link [3].
Proximity sensor
This is a sensor that has the ability to detect
a nearby object without any contact
physically through the emission of
electromagnetic radiation and looks for
variations in return signal or changes in the
field. The proximity sensor may have a long
functional life and high reliability due to the
absence of mechanical components and lack
of physical contact between the sensed
object and the sensor. This type of sensor is
used in machine vibration monitoring to
determine the changes in the distance
between support bearing and a shaft. The
exact point at which a target can be detected
is determined by the surface area, size, and
type of the metal [4]. The following chart
shows the field of sensing for standard
target:
Figure 3: Sensing field for standard target
[4]
Motion Sensor
Upon detection of motion, the motion sensor
produces an electrical signal based on which
some actions are taken. A motion sensor
emits the microwaves or radio waves across
a room which strikes on the object nearby
and reflect it back to the sensor detector.
When the object moves in an area controlled
by the motion sensor, the sensor determines
frequency shift in the wave when it returns
to the sensor detector, which would show
that the wave has hit an object moving [1].
This device has the ability to understand
these changes and convey an electrical
signal to the light or alarm system.