22 Questions
What is the primary source of gross error?
Human mistakes in reading and recording
How can instrumental errors be avoided?
By selecting a suitable instrument for the particular measurement application
What is the main reason for environmental errors?
Environmental effects on instrument
What kind of errors can be avoided by using the proper correction factor and information supplied by the manufacturer of the instrument?
Environmental errors
What is the primary purpose of calibrating an instrument?
To correct for instrumental errors
What is the purpose of using mirrors or knife edged pointers in instruments?
To eliminate observational errors
What is the main difference between systematic errors and gross errors?
Systematic errors are due to instrumental shortcomings, while gross errors are due to human mistakes
What type of error occurs due to unknown causes, even when all systematic errors have been accounted for?
Random error
What is the purpose of taking more than one reading of the same quantity?
To minimize gross errors
What is the definition of absolute error?
The difference between the measured value and the true value
What is the primary reason for classifying errors into different types?
To identify the sources of errors and develop strategies to minimize them
What is the relative error?
The ratio of absolute error to the true value of the quantity
What is the primary limitation of gross error?
It can be minimized by taking care while reading and recording
What is the purpose of making a new calibration under local conditions?
To reduce environmental errors
What is the absolute error in the measurement of a voltage with a true value of 1.50 V and an indicated value of 1.46 V?
0.04 V
What is a common source of observational error?
Parallax error while reading a meter
What is the relative error in a measurement?
The ratio of absolute error to original value
What can be used to reduce observational errors?
Instruments with mirrors
A measurement instrument has a scale range of 0-2.50 V. If the true value is 1.50 V, what is the maximum absolute error possible?
1.50 V
What is the primary difference between systematic and random errors?
Systematic errors are repeatable, while random errors are not
What is the purpose of a concept map in understanding errors in measurement?
To visualize the different types of errors
What is the relationship between the absolute error and the relative error?
Relative error is the ratio of absolute error to original value
Study Notes
Types of Measurement Errors
- Errors occur due to human carelessness, instrument limitations, and environmental effects
- Classified into three types:
- Gross Errors
- Systematic Errors
- Random Errors
Gross Errors
- Occur due to human mistakes in reading, calculating, and recording data
- Can be minimized by:
- Taking care while reading and recording data
- Taking multiple readings of the same quantity by different persons
Systematic Errors
- Instrumental Errors:
- Due to inherent shortcomings in instruments and misuse of instruments
- Can be avoided by:
- Selecting a suitable instrument for the application
- Applying correction factors after determining instrumental error
- Calibrating instruments against a standard
- Environmental Errors:
- Arise from environmental effects on instruments (e.g. temperature, humidity, magnetic fields)
- Can be avoided by:
- Using correction factors and information supplied by the manufacturer
- Using arrangements that keep surrounding conditions constant
- Making new calibrations under local conditions
Observational Errors
- Occur due to carelessness of operators while taking readings
- Sources of observational errors:
- Parallax error while reading a meter
- Wrong scale selection
- Habits of individual observers
- Can be eliminated by using instruments with mirrors, knife-edged pointers, and digital display instruments
Random Errors
- Due to unknown causes, even after accounting for systematic errors
- Occur in high-accuracy work, due to:
- Friction in instrument movement
- Parallax errors between pointer and scale
- Mechanical vibrations
- Hysteresis in elastic members
Absolute and Relative Errors
- Absolute Error: difference between measured value and true value of a variable
- Relative Error: ratio of absolute error to true value of the quantity to be measured
This quiz covers the topic of measurement errors in electrical measurements, including types of errors such as gross error, systematic errors, and random errors.
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