about sensors, their types are the best thing to do that for the first thing in the future and I will send you the best way to get the best way to get to know if you have any questions or comments
2. Proximity switches
• consists of an element that changes either its state or an analog signal
when it is close
• operate based on magnetic, capacitive, inductive, ultrasonic, eddy
current, or photo-optic effects
Photo sensitive Device
Reed Switch
Microswitch
3. Hall Effect sensor
• When a beam of charged particles passes through a magnetic field,
forces act on the particles and the beam is deflected from its straight
line path
• current flowing in a conductor is like a beam of moving charges and
thus can be deflected by a magnetic field.
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𝐵𝐼
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4. • immune to environmental contaminants and can be used under
severe service conditions
5. Tachogenerator
• used to measure angular velocity
• As the wheel rotates, so the teeth move
past the coil and the air gap between the coil and the ferromagnetic
material changes. We have a magnetic circuit with an air gap which
periodically changes
• Thus the flux linked by a pick-up coil changes. The resulting cyclic
change in the flux produces an alternating e.m.f. in the coil.
6. Tachogenerator is essentially an a.c. generator. It consists of a coil, termed the
rotor, which rotates with the rotating shaft.
pulse-shaping signal conditioner can be used to transform the output into a sequence of pulses
which can be counted by a counter, the number counted in a particular time interval being a
measure of the angular
velocity
7. Pyroelectric sensors
• crystalline materials which generate charge in response to heat flow.
• material is heated to a temperature just below the Curie temperature
• an electric field and the material cooled while remaining in the field,
electric dipoles within the material line up and it becomes polarized
8. • When the pyroelectric material is exposed to infrared radiation, its
temperature rises and this reduces the amount of polarization in the
material, the dipoles being shaken up more and losing their alignment
Pyroelectric sensor thus behaves as a charge generator which generates charge
when there is a change in its temperature as a result of the incidence of infrared
radiation
9. Force Measurement- Strain gauge load cell
• based on the use of electrical resistance strain gauges to monitor the
strain produced in some member when stretched, compressed or
bent by the application of the force
11. Piezoelectric sensors
• materials are ionic crystals, which when stretched or compressed
result in the charge distribution in the crystal changing so that there is
a net displacement of charge with one face of the material becoming
positively charged and the other negatively charged.
• displacement is proportional to the applied force F.
• q =kx = SF
capacitance C =
12. pressure sensor- Tactile sensor
• sensor is used on the ‘fingertips’ of robotic ‘hands’ to determine
when a ‘hand’ has come into contact with an object.
• Eg. piezoelectric polyvinylidene fluoride (PVDF) film
When pressure is applied to the upper PVDF film its vibrations are affected and
the output alternating voltage is changed.
13. Flow Meter-Turbine meter
• angular velocity being approximately proportional to the flow rate
• The rate of revolution of the rotor can be determined using a
magnetic pick-up.
• The pulses are counted and so the number of revolutions
of the rotor can be determined
16. Thermistors
• material made from mixtures of metal oxides, such as those of
chromium, cobalt, iron, manganese and nickel.
• are rugged and can be very small,
so enabling temperatures to be
monitored at virtually a point
17. Light sensors
• Photodiodes are semiconductor junction diodes
• are connected into a circuit in reverse bias, so giving a very high
resistance
• With no incident light, the reverse current is almost negligible and is
termed the dark current
• When light falls on the junction, extra hole–electron pairs are
produced and there is an increase in the reverse current and the
diode resistance drops
• The reverse current is very nearly proportional to the intensity of the
light
• Photodiodes have a very fast response to light.
