Corporate Profile 47Billion Information Technology
Ppt1
1. UNIVERASAL COLLEGE OF
ENGINEERING & TECHNOLOGY
Patel Varun Nitinkumar
(090460111037)
Electronics Measurements &
Instrumentation Laboratory
2. Transducer
• Transducer
– A transducer is a device that converts one type of energy to another.
– a device that converts a primary form of energy into a corresponding
signal with a different energy form
• Primary Energy Forms: mechanical, thermal, electromagnetic, optical,
chemical, etc.
– take form of a sensor or an actuator.
• Sensor (e.g., thermometer)
– a device that detects/measures a signal or stimulus
– acquires information from the “real world”
• Actuator (e.g., heater)
– a device that generates a signal or stimulus
3. Found in Day to Day Life
– Many people think of a transducer as being some sort
of technical device, but they can be found in many
places in day to day life.
– A microphone, for example, converts sound waves that
strike its diaphragm into an analogous electrical signal
that can be transmitted over wires.
– Most transducers have an inverse that allows for the
energy to be returned to its original form. Audio
cassettes, for example, are created by using a
transducer to turn the electrical signal from the
microphone pick-up — which went through a
transducer to convert the sound waves into an
electrical signal — into magnetic fluctuations on the
tape head.
4. • Other transducers turn one type of energy into another form,
not to measure something in the external environment or to
communicate information, but rather to make use of that
energy in a more productive manner.
• A light bulb, for example, converts electrical energy into
visible light. Electric motors are another common form of
electromechanical transducer, converting electrical energy
into kinetic energy to perform a mechanical task.
• The inverse of an electric motor — a generator — also is a
transducer, turning kinetic energy into electrical energy that
can then be used by other devices.
5. Efficiency of transducers
• As in all energy conversions, some energy is lost
when transducers operate. The efficiency of a transducer is
found by comparing the total energy put into it to the total
energy coming out of the system. Some transducers are very
efficient, and others are extraordinarily inefficient.
• A radio antenna is one example of an efficient transducer. The
antenna acts as a transducer to turn radio frequency power
into an electromagnetic field. When the antenna is operating
well, this process can be more than 80% efficient.
• Most electrical motors, by contrast, are less than 50%
efficient. A common light bulb, because of the amount of
energy that is lost as heat, is less than 10% efficient .
6. What are Electrical Transducers?
• The transducers that convert the mechanical input signals of
the physical quantity into electrical output signals are called
as electrical transducers.
• The input given to the electrical transducers can be in the
form of the displacement, strain, velocity, temperature, flow
etc and the output obtained from them can be in the form of
current, voltage and change in resistance, inductance and
capacitance.
• The output can be measured easily and it is calibrated against
the input, thus enabling the measurement of the value of the
input.
7. Example of Electrical Transducers
• Potentiometers: They convert the change in
displacement into change in the resistance, which can
be measured easily.
• Bridge circuits: These convert the physical quantity to
be measured into the voltage.
• Wheatstone bridge: It converts the displacement
produced by the physical quantity to the current in the
circuit.
• Variable Capacitance Transducers: These comprise of
the two parallel plates between which there is
dielectric material like air. The change in distance
between the two plates produced by the displacement
results in change in capacitance, which can be easily
measured
8. • Variable Resistance Transducers : There is change in
the resistance of these sensors when certain physical
quantity is applied to it. It is most commonly used in
resistance thermometers or thermistors for
measurement of temperature.
• Magnetic sensors: The input given to these sensors is
in the form of displacement and the output obtained is
in the form of change in inductance or reluctance and
production of the eddy currents.
• Piezoelectric transducers: When force is applied to
these transducers, they produce voltage that can be
measured easily. They are used for measurement of
pressure, acceleration and force
9. • Strain gauges: When strain gauges are strained or stretched
there is change in their resistance. They consist of the long
wire and are able to detect very small displacements
produced by the applied force or pressure.
• Photo electric transducers: When the light is applied to
these transducers they produce voltage.
• Linear variable differential transformer (LVDT): LVDT is the
transformer consisting of the primary and the secondary
coil. It converts the displacement into the change in
resistance.
• Ultrasonic Transducers: These transducers use the
ultrasonic or ultrasound waves to measure parameters like
fluid level, flow rate etc.
10. Circuits of some Electrical Transducer
• Thermistor Circuit
A Thermistor is a temperature dependent resistor. When temperature
changes,the resistance of the thermistor changes in a
predictable way.
when you refer to this thermistor ,you would say it has 5kW at room
temperature.
Resistance of thermistor at
T (oC) R (ohm)
Resistance of themistor at 0 16330
different temp. is as shown 25 5000
in the table. 50 1801
11. Operational Amplifiers
properties
• open-loop gain: ideally infinite: practical values 20k-200k
–high open-loop gain virtual short between + and - inputs
• input impedance: ideally infinite: CMOS opamps are close to ideal
• output impedance: ideally zero: practical values 20-100
• zero output offset: ideally zero: practical value <1mV
• gain-bandwidth product (GB): practical values ~MHz
–frequency where open-loop gain drops to 1 V/V
• Commercial opamps provide many different properties
– low noise
– low input current
– low power
– high bandwidth
– low/high supply voltage
– special purpose: comparator, instrumentation amplifier
