12 Questions
Which of the following is an example of using null methods of measurement?
Measuring weight with a balance
What is the approach in indirect measurement methods?
Establishing empirical relations
What is the purpose of null methods of measurement?
To compare the unknown quantity with a known quantity
How does indirect measurement work in the context of eliminating bacteria from a fluid?
By measuring the temperature of the fluid
In what way do comparison methods differ from null methods in measurement?
Null methods eliminate the action of unknown quantity by a known counter quantity
Why are indirect measurement methods preferred for difficult-to-measure parameters?
They establish an empirical relation with easily measurable related parameters
What is the primary purpose of measurement?
To express the value of an unknown quantity in terms of a standard unit
What is a standard in the context of measurement?
Both A and B
What is a measuring instrument?
A device used to compare an unknown quantity with a standard unit
In direct measurement methods, how is the unknown quantity measured?
By directly measuring the unknown quantity itself
What is the purpose of the deflection method?
To directly indicate the value of the unknown quantity
What are the different types of comparison methods mentioned in the text?
Null methods and differential methods
Study Notes
Measurement Basics
- Measurement is a quantitative comparison between a given quantity and a standard unit of the same kind.
- The result of measurement is expressed by a pointer deflection over a predefined scale or a number representing the ratio between the unknown quantity and the standard.
- A standard is defined as the physical personification of the unit of measurement or its submultiple or multiple values.
Direct Measurement Methods
- Direct measurement methods involve measuring the unknown quantity directly without comparing it with a standard.
- Examples include measurement of weight by a balance, measurement of resistance, capacitance, and inductance by bridge circuits.
Comparison Methods
- Comparison methods involve direct comparison of the unknown quantity with a standard of the same kind.
- Examples include measurement of e.m.f by comparison with the e.m.f of a standard cell.
Null Method
- In the null method, the action of the unknown quantity upon the instrument is reduced to zero by the counter action of a known quantity of the same kind.
Differential Method
- In the differential method, the quantity to be measured is compared with a known quantity and the difference between these two is made zero.
Indirect Measurement Methods
- Indirect measurement methods involve comparing the unknown quantity with a standard using a calibrated system.
- These methods are used when the desired parameter to be measured is difficult to measure directly, but has a relation with another parameter that can be easily measured.
- Example: measuring bacteria elimination by measuring the temperature of the fluid, as the elimination is directly dependent upon the temperature.
Deflection Method
- In the deflection method, the value of the unknown quantity is directly indicated by the deflection of a pointer on a calibrated scale.
Test your knowledge on measurement, standard units, and devices used for comparison. Understand the concept of expressing measurement results via pointer deflection or numerical ratios.
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