Measuring instruments may be defined as device for determining the value or magnitude of quantity or variable.To know about ‘Measuring instruments’ in detail, visit http://electricalfundablog.com/blog/measuring-instrument/665/. Here in this post, we will learn about the methods of measurement.
The methods of measurement may be broadly classified into two categories.
Direct Methods of measurement.
In this method, the unknown quantity (also called the measurand) is directly compared against a standard. The result is expressed as a numerical number and a unit.
The standard, in fact, is a physical embodiment of a unit. Direct methods of measurement are quite common for the measurement of physical quantities like length, mass and time.
The indirect methods of measurement involves measurement by help of a transducer which converts the quantity to be measured into an analog or digital signal. These signals are processed by some intermediate device, which finally present the absolute result of the measurement.
Methods of Measurement by direct type of methods are not always possible, feasible and practicable. In most of the cases these methods of measurement are inaccurate as they involve human factors. They are also less sensitive. Hence direct methods are not preferred and are rarely used.
To measure the length of a bar, the unit of length is taken as meter in SI unit. A human being can make direct length comparisons with a preciseness of about 0.25 mm. The direct method for measurement of length can be utilized with a good degree of accuracy but when it comes to measurement of mass, the problem becomes much more intricate. It is just not possible for human beings to distinguish between wide margins of mass.
The indirect methods of measurement consists of a transducing element, which converts the quantity to be measured in an analog form. The analog signal is then processed by some intermediate means and is then fed to the end devices, which present the results of the measurement.