Sensors and Transducers QA

7/24/2019 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.

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Sensors and Transducers QA