Which of the following transducers are not linear ? i. thermistor
ii. thermocouple
iii. IC sensor
i, ii
The IC sensor is the linear one — that is its whole reason for existing — so the non-linear pair is the thermistor and the thermocouple, option 1.
| Sensor | Law | Linear? |
|---|---|---|
| Thermistor | \(R_{T}=R_{0}e^{\beta\left(\frac{1}{T}-\frac{1}{T_{0}}\right)}\) | ✗ Exponential |
| Thermocouple | Polynomial in T, several terms | ✗ Mildly curved |
| IC sensor | \(V=10\ \text{mV}/^{\circ}\text{C}\times T\) | ✓ Linear by design |
The thermistor is the most non-linear of the three by a wide margin. Its resistance falls exponentially with temperature, because the carrier population in a semiconductor rises exponentially as electrons are excited across the band gap. Over a 100 °C span the resistance can change by a factor of fifty, which gives excellent sensitivity but a scale that must be linearised in software or by a shunt resistor.
The thermocouple is only mildly non-linear, but non-linear nonetheless. The Seebeck coefficient itself varies with temperature, so the output is described by a polynomial — standards tables use up to nine or ten terms for accurate work. A type K couple's 41 µV/°C is a convenient average, not a constant.
Why the IC sensor is linear. It does not rely on any bulk material property but on a designed circuit: the difference in base-emitter voltage between two transistors run at different current densities is
\(\Delta V_{BE}=\dfrac{kT}{q}\ln\left(\dfrac{J_{1}}{J_{2}}\right)\)
which is exactly proportional to absolute temperature, since the logarithm is a fixed ratio set by the circuit geometry. On-chip amplification scales this to a convenient 10 mV/°C, and the result needs no linearisation at all.
The trade-off across the three is the useful takeaway: the IC sensor is linear and easy to use but limited to roughly −55 to +150 °C, since it is itself a silicon circuit; the thermistor gives the greatest sensitivity over a narrow band; and the thermocouple, though non-linear and low in output, works from cryogenic temperatures to well over 1500 °C, which neither of the others can approach.
Hence, the non-linear transducers are the thermistor and the thermocouple.
Similar Questions
Which of the following sensors has excellent linearity ?
Consider the following statements associated with electrical and electronic transducers
A. Little power is consumed by transducer
B. Mass intertia effects are not minimized
C. The response time is small
D. Transmission and processing the signal for the purpose of measurement are easier.
Choose the correct answer from the options given below:
Incorrect statements regarding measurement are given :
A. Hot wire anemometer is used to measure displacement
B. Hall effect is used to measure current
C. LVDT is used to measure acceleration and gas flow
D. Piezoelectric Transducer is used to measure acceleration
Choose the correct answer from the options given below:
Match List I with List II
LIST I LIST II A. Relative error I. The ability of tde device to give identical O/P when repeated measurements are made witd tde same I/P signal B. Precision II. The ratio of difference between measured value and tde true value to tde true value of tde measurand C. Caliberation III. The smallest increment in measure tdat can be detected witd certainity by tde instrument D. Resolution IV. The process of making adjustments or tde scale so tdat tde instrument reading conform to an accepted standard. Choose the correct answer from the options given below:
Match the following lists :
List – I List – II a. Electromechanical Device i. Seismic Device b. Optical Device ii. Piezo-electric c. Gyroscopic device iii. Interferometers d. Absolute motion device iv. Aerospace vehicle Choose the correct answer from the codes given below:
Consider the following transducers or transducer systems :
(a) Float elements
(b) Seismic system
(c) Gyroscope
Arrange the above transducers/systems in decreasing order of the availability of possible number of output signals.
The fundamental law that is used in temperature measurement is known as
Assertion (A) : Normally, some standard signal conditioner and display devices are used with a transducer, unless they are custom-built to suit the requirements of the transducers.
Reason (R) : A transducer is a device which receives energy in one form and transfer it to a convenient form.
Select your answer using the codes given below :
The mechanical elements that are used to convert the applied force into a displacement are called :
A device used to convert a non-electrical quantity into an electrical signal is called :
Important Questions from Basics of Transducers
_____ converts mechanical displacement into electrical signals.
Which of the following sensors has excellent linearity ?
Consider the following statements associated with electrical and electronic transducers
A. Little power is consumed by transducer
B. Mass intertia effects are not minimized
C. The response time is small
D. Transmission and processing the signal for the purpose of measurement are easier.
Choose the correct answer from the options given below:
Incorrect statements regarding measurement are given :
A. Hot wire anemometer is used to measure displacement
B. Hall effect is used to measure current
C. LVDT is used to measure acceleration and gas flow
D. Piezoelectric Transducer is used to measure acceleration
Choose the correct answer from the options given below:
Match List I with List II
LIST I LIST II A. Relative error I. The ability of tde device to give identical O/P when repeated measurements are made witd tde same I/P signal B. Precision II. The ratio of difference between measured value and tde true value to tde true value of tde measurand C. Caliberation III. The smallest increment in measure tdat can be detected witd certainity by tde instrument D. Resolution IV. The process of making adjustments or tde scale so tdat tde instrument reading conform to an accepted standard. Choose the correct answer from the options given below:
