Sensors and Transducers QA
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ETU 07103: Electronic Devices Dr. Msumba JA
Dar es Salaam Institute of Technology
Department of Electronics and Telecommunications Engineering
Electronics Section
Questions& Answers for Transducers and Sensors
Module Name: Electronic Devices
Module Code : ETU 07103
Class: BENG 15 (ETE1, ETE2 & CO)
Module Master: Dr. J.A. Msumba
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Q51 When a transducer converts a measurable quantity (sound pressure level, optical
intensity, magnetic field, etc) to an electrical voltage or an electrical current we call it a
oSensoroActuatoroInstrumentoTransducer gain
Q52 When the transducer converts an electrical signal into another form of energy, such
as sound (which incidentally, is a pressure field), light, mechanical movement, it is
called Anactuator
Model sensor
Sensor
Instrument
Q53 What is the difference between a transducer and a sensor?
Transduceris a device that converts a primary form of energy into a
corresponding signal with a different energy form while a sensor isdevice that responds to a physical stimulus such as heat, light
,magnetism, or particular motion and transmit result impacts such as
measurement or operating a control
Q54 What are two advantages and two disadvantages of measuring temperature using
thermocouples?
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Advantages: They are inexpensive, rugged and
reliable, can be used over a wide
temperature range.
Disadvantages: Low output voltage, low sensitivity, non-
linearity, and electrical connections.
What is the difference between a thermocouple and a thermistor?
A thermistor is made of a semiconductor material that exhibits a
predictable and repeatable change in resistance as temperature is
changed while in a thermocouple when a temperature differential
exists across the length of a metal, a small voltage differential
will exist due to the migration of electrons in the metal. By
joining two dissimilar metal wires together at one end, a small
current will be induced at the junction due to differences in the
molecular structure of the metals.
Q55 A transducer is normally designed to sense a specific measurand or to respond only
to that particular measurand. A complete knowledge of the electrical andmechanical characteristics of the transducer is of great importance while choosing a
transducer for a particular application. Often, it is deemed essential to get details of
these characteristics during the selection of instrumentation for the experiment
concerned. Briefly explain the basic requirements of a transducer.
Ruggedness - Ability to withstand overloads, with safety stop
for overload protection.
Linearity - Ability to reproduce input-output characteristics
symmetrically and linearly. Overall linearity is the main factor
considered.
Repeatability- Ability to reproduce the output signal exactly
when the same measurand is applied repeatedly under same
environmental conditions.
Convenient Instrumentation -Sufficiently high analog output signal
with high signal to noise ratio; digital output preferred in many
cases.
High Stability and Reliability- Minimum error in measurement,
unaffected by temperature, vibrations and environmental
variations.
Good Dynamic Response -Output is faithful to input when taken as a
function of time. This effect is analyzed as the frequency
response.
Excellent Mechanical Characteristics -This can affect the
performance in static, quasi-static, and dynamic states.
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Q56 What are the three important parameters of a transducer?
static response,
dynamic response,
environmental factors and
reliability
Q57 What are two advantages and two disadvantages of measuring temperature usingthermocouples?
Advantages:
they are inexpensive,
rugged and reliable,
can be used over a wide temperature range
Disadvantages
low output voltage,
low sensitivity,
non-linearity, and
electrical connections
Q58 What are the factors used in selecting the transducers (mention at least six)
Operating Principle
Sensitivity
Operating Range
Accuracy
Cross sensitivity
Errors
Transient and frequency response
Loading Effects
Environmental Compatibility
Insensitivity to unwanted signals
Q59 Temperature transducers are used extensively in process industries such as chemical,
food and pharmaceuticals, where control of temperature during manufacturing is
important. What are the commonly used temperature transducers ?
Q60 a) What are the characteristics of transducers?
Linearity
Repeatability
Accuracy
High stability and reliability Speed of response
Sensitivity
Small size
b) There are four ways in which the transducers can be classified. What are the classifications of
transducers?
Active and passive transducers,
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On the basis of transduction principle used,
Primary and secondary transducer,
Transducers and inverse transducers.