Electrical and Electronics. Measurements and Instrumentation. Prithwiraj Purkait. Professor. Department of Electrical Engineering and. Dean, School of. Electronic Instruments for Measuring Basic Parameters: Amplified DC meter, AC Modern Electronics Instrumentation & Measurement Techniques, by Albert D. PDF | On May 16, , Ramaprasad Panda and others published Electrical & Electronics Measurements & Measuring Instruments.
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engineers in other areas who may use electronics in their instrumentation. The revisions in As in the earlier volume which it supersedes, "Electronic Measure-. ence—the dark night of the soul, the call for help, the responding voice, the.. clashes with any other item, Rumi wa Electrical and Electronics Measurements . Electronic Measurement and Instrumentation L-T-P: Credits: 3 Electrical Measurements Standards of Measurement & Errors, Review of indicating and.
The most common error is the parallax error introduced in reading a meter scale, and the error of estimation when obtaining a reading from a meter scale. For example, an observer may always introduce an error by consistently holding his head too far to the left while reading a needle and scale reading. In general, systematic errors can also be subdivided into static and dynamic Errors.
Electrical and Electronics Measurements and Instrumentation
Static errors are caused by limitations of the measuring device or the physical laws governing its behavior. Dynamic errors are caused by the instrument not responding fast enough to follow the changes in a measured variable.
What is the method used to calculate the errors in an instrument? It involves connecting a measuring instrument into the system under consideration and observing the resulting response on the instrument.
The measurement thus obtained is a quantitative measure of the so-called "true value" since it is very difficult to define the true value, the term "expected value" is used. Any measurement is affected by many variables; therefore the results rarely reflect the expected value. For example, connecting a measuring instrument into the circuit under consideration always disturbs changes the circuit, causing the measurement to differ from the expected value.
Some factors that affect the measurements are related to the measuring instruments themselves. Other factors are related to the person using the instrument. The degree to which a measurement nears the expected value is expressed in terms of the error of measurement. Error may be expressed either as absolute or as percentage of error.
Describe the function of the DC-Voltmeter and multi range voltmeter and explain their operation? Ans: DC-Voltmeter A basic D'Arsonval movement can be converted into a dc voltmeter by adding a series resistor known as multiplier, as shown in the figure. The function of the multiplier is to limit the current through the movement so that the current does not exceed the full scale deflection value. A dc voltmeter measures the potential difference between two points in a dc circuit or a circuit component.
To measure the potential difference between two points in a dc circuit or a circuit component, a dc voltmeter is always connected across them with the proper polarity. The value of the multiplier required is calculated as follows. Im: full scale deflection current of the movement Rm : internal resistance of movement Rs : Multiplier resistance V: full range voltage of the instrument From the circuit of Fig.
The above equation is also used to further extend the range in DC voltmeter'. Fig 4. In range selector selects the This arrangement is advantageous compared to the previous one, because all multi1llier resistances except the first have the standard resistance value and are also easily available in precision tolerances.
The first resistor or low range multiplier, R4, is the only special resistor which has to be specially manufactured to meet the circuit requirements. Explain the working of solid state voltmeter?
This is a directly coupled very high gain amplifier. The 0. A 10 k potentiometer is connected between these two offset null terminals with its centre tap connected to a - 5V supply. This potentiometer is called zero set and is used for adjusting zero output for zero input conditions. The two diodes used are for IC protection. Under normal conditions, they are non-conducting, as the maximum voltage across them is l0 mV.
If an excessive voltage, say more than mV appears across them, then depending upon the polarity of the voltage, one of the diodes conducts and protects the IC.
A A scale of 50 - A full scale deflection can be used as an indicator. Ro is adjusted to get maximum full scale deflection. Draw the block diagram of the measuring system and explain the function of each stage of this system? Ans: The generalized measuring system consists of three main functional elements.
They are, 1.
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Primary sensing element, which senses the quantity under measurement. Variable conversion element, which modifies suitably the output of the primary sensing element 3.
Data presentation element that renders the indication on a calibrated scale. Primary Sensing Element The measurement first comes into contact with primary sensing element where the conversion takes place. This is done by a transducer which converts the measurement or measured quantity into a usable electrical output.
The transduction may be from mechanical, electrical or optical to any related form. Variable Conversion Element The output of the primary sensing element is in the electrical form suitable for control, recording and display.
For, the instrument to perform the desired function, it may be necessary to convert this output to some other suitable for preserving the original information. This function is performed by the variable conversion element.
A system may require one or more variable conversion suitable to it. Ro is adjusted to get maximum full scale deflection. Variable Conversion Element The output of the primary sensing element is in the electrical form suitable for control.
Explain the types of test signals used in determining dynamic measurements applied to a system. In case of spacecrafts. V equipment. The element that follows the primary sensing element in a measurement system is called signal conditioning element. The stage that follows the signal conditioning element and data transmission element collectively is called the intermediate stage.
Here the variable conversion element and variable manipulation element are collectively called as Data conditioning element or signal conditioning element. Here the voltage amplifier acts as a variable manipulation element since it amplifies the voltage.
Data Presentation Element The display or readout devices which display the required information about the measurement. The output is the same voltage but of higher value. Control or analysis purposes. Here the information of the measurand has to be conveyed for. A system may require one or more variable conversion suitable to it. This function is performed by the variable conversion element. The standard test signals used for time domain analysis are as follows.
The continuous time impulse input is given by. A sinusoidal signal is an example of a periodic signal. This specification has three significant figures.
Conformity Ans: This specification has two significant figures. From the above illustration. Let us consider an example of measuring resistance of a resistor which has a true resistance of If the measured voltage is specified as Significant figures indicate the precision of the measurement and the magnitude of the measurements. The measured value should be expressed in more number of significant figures because the more significant figures the higher will be the precision.
Explain the terms i. If the multi meter indicates the resistance value as Consider an example in which the measured voltage across a resistor in a circuit is specified as 50 V. If a measuring instrument consistently and repeatedly provides a value as close to the true value of the measured quantity as an observer can estimate the true value from its scale reading then this characteristic refers to the conformity of the measurement.
It indicates that the measured voltage may be close to 49 V or 51 V. Figure shows the basic circuit of an aryton shunt. The series combination of resistor R6 and the meter movement is in parallel with resistor R1.
Hence the sensitivity of the meter movement is increases. This reduces the sensitivity of meter movement. When the switch is in position "3". R3 and the meter movement is in parallel with R1 when the switch SW is connected to position "1". It avoids the possibility of using the meter in the circuit without a shunt.
This is the most important merit of the aryton shunt. The resistors R1. From the above figure. What is ayrton shunt?
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Describe it with a neat sketch. Now the current flowing through the shunt is very little whereas the current flowing through the meter is very high. Aryton shunt: It is also known as universal shunt. Then the output signal of integrator will have negative slope. Decimal counter 5.
The major blocks of a dual slope integrating type DVM dual slope analog to digital converter are. Explain with a neat block diagram of a dual slope digital voltmeter?
Basic Principle: An op-amp employed as an integrator 2. A level comparator 3. Block of logic circuitry. The slope of the integrated signal is proportional to the input voltage under measurements.
Oscillator for generating time pulses 4.
Depending on the requirement the accuracy and sped can be varied. Advantages 1. This makes the switch Si. Si is in closed condition. As soon as. This forms the basic type of series ohm meter..
From the above equation. As soon as it reaches its maximum count that is the counter is preset to run for a time period r. During this discharging period the counter indicates the count. Now the counter counts the number of pulses fed to it.
The switch Sr is in open condition and the switch.. Once the output of the integrator becomes greater than zero. Explain the constructional details and differentiate between Ohmmeter type and shunt type.
And the counted pulses are displayed which directly gives the input voltage. When the gate opens the output of the oscillator clock pulses are allowed to pass through it and applied to the counter. This again makes the output of the comparator to change its state which in turn closes the gate. This technique exhibits excel lent noise rejection since the integration process eliminates both noise and super imposed A.
By connecting different known values of the unknown resistance to terminals A and B. Since this value affects the calibration of the scale. The accuracy of the Instrument can be checked by measuring different values of standard resistance. There by bringing the pointer back to "0" ohms on the scale' It is also possible to adjust the full scale deflection current without the shunt R2 in the circuit.
The variable Shunt resistor R2 across the movement is adjusted to counteract the drop in battery Voltage. To mark the "0" reading on the scale. The Position of the pointer on the scale is then marked "0" ohms.
Due to this. The internal resistance of the coil Rm is very low compared to R1 When R2 is varied. The series ohmmeter is a simple and popular design. Flag for inappropriate content. Related titles. Guideline for Report Writing and Error Calculation. Electronic Instrumentation 2nd Edition By P. Jump to Page. Search inside document. Aditya Pujara. R-wah Larounette.
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Advantages 1. Ans: DC-Voltmeter A basic D'Arsonval movement can be converted into a dc voltmeter by adding a series resistor known as multiplier, as shown in the figure.
For example, in the D'Arsonval movement friction in the bearings of various moving components, irregular spring tensions, stretching of the spring or reduction in tension due to improper handling or over loading of the instrument. Some factors that affect the measurements are related to the measuring instruments themselves.
A measure of the consistency or repeatability of measurements, i. Fortunately, general description of instrument systems responses can be usually be adequately covered using the linear treatment. This is a directly coupled very high gain amplifier. Since the modifications of the current sensor are compact, it is practical to have all three functions in a single instrument with multiple ranges of sensitivity.
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