UNIT IV- BASICS OF MEASUREMENT AND INSTRUMENTATION PART A 1. Write the staticcharacteristics of measurement. (N/D 15) (N/D 13) Accuracy, precision, sensitivity, linearity, Repeatablity. 2. Define static error in measurements. ( N/D 14) Static error is defined as the difference between the measured value and the true value of the quantity under measurement. A = Am -At, Where, A - Absolute static error of quantity, At - true value of quantity, Am - Measured value of quantity. 3. What is a transducer? Give example.( N/D 14 M/J 13) Transducer is a device which converts the physical quantity into an electrical quantity. ex: Thermocouple - which converts the temperature into voltage. 4. What is an LVDT? What are the advantages of LVDT? (M/J 16 N/D 13) It is a three coil inductive transducer operated in the differential mode. It consists of a primary coil and two secondary coil windings on a cylindrical former. The primary coil is connected to an alternating source whereas the differential output is taken from the two secondary coils. Advantages: Wide range of linearity, Change of phase by 180 Deg When the core passes through the center position, Full-scale displacement is 0.1- 250mm, Sensitivity is 0.5- 2 mV. 5.A Thermistor has a resistance temperature coefficient β of -5%/ºC. If the resistance of the thermistor is 100Ω at º C ,What is the resistance at º C? (A/M 15) Temp difference=35-25=10 deg Decrease per degree=5% soOhmic Decrease 5*10=50 Ω Resistance at 35 º C = 100-50=50Ω 6. What is a piezoelectric effect?(A/M 15)(N/D16) When a piezoelectric material is subjected to stress or force, it generates an electrical potential or voltage proportional to the magnitude of the force. This makes this type of transducer ideal as a converter of mechanical energy or force into electric potential. . 7.What is a Thermistor? Where do you deploy it. (N/D15) (M/J 13) Thermistor is a non metallic resistor used to measure the variation of temperature with lower power dissipation. Temperature sensing applications 8. Define accuracy and resolution of a measuring instrument.(N/D16) Accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's true value. Resolution is the ability of the measurement system to detect and faithfully indicate small changes in the characteristic of the measurement result. 9. How is the dynamic behavior of a measuring system determined? Name any common inputs to the system? (M/J 16) The dynamic characteristics of any measurement system are (i)Speed of response and Response time (ii)Lag (iii) Fidelity (iv) Dynamic error
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UNIT IV-BASICS OF MEASUREMENT AND INSTRUMENTATION PART … · UNIT IV-BASICS OF MEASUREMENT AND INSTRUMENTATION PART A 1. Write the staticcharacteristics of measurement. (N/D 15)
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UNIT IV- BASICS OF MEASUREMENT AND INSTRUMENTATIONPART A
1. Write the staticcharacteristics of measurement. (N/D 15) (N/D 13)Accuracy, precision, sensitivity, linearity, Repeatablity.2. Define static error in measurements. ( N/D 14)Static error is defined as the difference between the measured value and the true value of the quantityunder measurement. A = Am -At, Where, A - Absolute static error of quantity, At - true value ofquantity, Am - Measured value of quantity.3. What is a transducer? Give example.( N/D 14 M/J 13)Transducer is a device which converts the physical quantity into an electrical quantity.ex: Thermocouple - which converts the temperature into voltage.4. What is an LVDT? What are the advantages of LVDT? (M/J 16 N/D 13)
It is a three coil inductive transducer operated in the differential mode. It consists of a primary coiland two secondary coil windings on a cylindrical former. The primary coil is connected to an alternatingsource whereas the differential output is taken from the two secondary coils.Advantages:
Wide range of linearity, Change of phase by 180 Deg When the core passes through the centerposition, Full-scale displacement is 0.1- 250mm, Sensitivity is 0.5- 2 mV.
5.A Thermistor has a resistance temperature coefficient β of -5%/ºC. If the resistance of thethermistor is 100Ω at ºC ,What is the resistance at º C? (A/M 15)Temp difference=35-25=10 deg Decrease per degree=5% soOhmic Decrease 5*10=50 ΩResistance at 35º C = 100-50=50Ω6. What is a piezoelectric effect?(A/M 15)(N/D16)When a piezoelectric material is subjected to stress or force, it generates an electrical potential or voltageproportional to the magnitude of the force. This makes this type of transducer ideal as a converter ofmechanical energy or force into electric potential..7.What is a Thermistor? Where do you deploy it. (N/D15) (M/J 13)Thermistor is a non metallic resistor used to measure the variation of temperature with lower powerdissipation. Temperature sensing applications8. Define accuracy and resolution of a measuring instrument.(N/D16)Accuracy of a measurement system is the degree of closeness of measurements of a quantity to thatquantity's true value.Resolution is the ability of the measurement system to detect and faithfully indicate small changes in thecharacteristic of the measurement result.9. How is the dynamic behavior of a measuring system determined? Name any common inputs tothe system? (M/J 16)The dynamic characteristics of any measurement system are (i)Speed of response and Response time(ii)Lag (iii) Fidelity (iv) Dynamic error
STATIC & DYNAMIC CHARACTERISTICS OF MEASUREMENT SYSTEM
The performance characteristics of an instrument are mainly divided into two categories:
i) Static characteristics
ii) Dynamic characteristics
Static characteristics:
The set of criteria defined for the instruments, which are used to measure the quantities which
are slowly varying with time or mostly constant, i.e., do not vary with time, is called ‘static
characteristics’.
The various static characteristics are:
i) Accuracy
ii) Precision
iii) Sensitivity
iv) Linearity
v) Reproducibility
vi) Repeatability
vii) Resolution
viii) Threshold
ix) Drift
x) Stability
xi) Tolerance
xii) Range or span
Accuracy:
It is the degree of closeness with which the reading approaches the true value of the quantity to
RAJESH KUMAR D
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1.Explain about static and dynamic characteristics of measurement system N/D 13.
RAJESH KUMAR D
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EE6353-Electrical Engineering and Instrumentation Unit-IV University 16 marks
be measured. The accuracy can be expressed in following ways:
a) Point accuracy:
Such accuracy is specified at only one particular point of scale.
It does not give any information about the accuracy at any other Point on the scale.
b) Accuracy as percentage of scale span:
When an instrument as uniform scale, its accuracy may be expressed in terms of scale range.
c) Accuracy as percentage of true value:
The best way to conceive the idea of accuracy is to specify it interms of the true value of the
quantity being measured.
Precision: It is the measure of reproducibility i.e., given a fixed value of a quantity, precision is a
measure of the degree of agreement within a group of measurements. The precision is composed
of two characteristics:
a) Conformity:
Consider a resistor having true value as 2385692 , which is being measured by an ohmmeter. But
the reader can read consistently, a value as 2.4 M due to the nonavailability of proper scale. The
error created due to the limitation of the scale reading is a precision error.
b) Number of significant figures:
The precision of the measurement is obtained from the number of significant figures, in which
the reading is expressed. The significant figures convey the actual information about the
magnitude & the measurement precision of the quantity. The precision can be mathematically