Introduction of Measurement
Hi, this is the first day of this course. Today you will learn basic knowledge of Metrology, Measurement, Terminologies, Basic Units of Measurement.
Measurement is a Natural part of everyday life. We express daily needs in size & weight, water and electricity are also metered.
A number of blood samples, active sub-stain in medicine also need to be precise.
I think it is impossible to describe anything without measuring it.
Room temperature, body weight, sunshine, chest width and so on..
Almost every company are concerned with Quality management in the process of Introducing their work
What is Metrology?
Metrology word derived from the Greek words Metro(means Measurement) and Logy(means Science).
Metrology includes all aspects with reference to measurements, whatever their level of accuracy.
Terminologies Used in Engineering
Some technical terms are difficult to understand, so the following terminology is quite helpful for further studies
Accuracy is the closeness between a test result and accepted value.
Bias is the difference between the expected value and the accepted reference value.
Calibration is the set of operations that establish under specified conditions, the relationship between values of quantities indicated by a measuring instrument or values represented by a material measure and the corresponding values realized by standards.
Drift is slow to change of a metrological characteristic of measuring instrument.
The output result from a measuring device to be magnified many times to make it more readable, called Magnification.
Precision is the closeness of agreement between independent test results obtained under stipulated conditions.
The smallest chance of the measured quantity which changes the indication of a measuring instrument is called Resolution.
Traceability means a measured result can be related to references.
Basic Fundamental Units of Measurement
We measure some physical or non-physical quantity by the mean of some output results. This output results express in some units. For example, we usually measure the length in millimeter or meter or kilometer.
But in a standard manner, every individual type of measurement expressed in a unique fundamental unit. According to the SI standard, we have seven basic fundamental units of seven basic measurement types. This type is expressed follows
The basic fundamental unit of mass is “Kg”. We also measure mass in Gram, Pound, Metric ton, Stone, Microgram, Carat, etc.
The basic fundamental unit of Time is “Sec(s)”. We also express time in seconds, minutes, hours, days, weeks, years, etc.
The basic fundamental unit of Electric Current is “Ampere(A)”.
Amount of Substance
The amount of Substance is a dimensionless expression of the number of particles in a particle or object. The basic fundamental unit of Amount of Substance is “Mole”. The amount of substance all called material quantity.
The SI unit of Illumination is “Candela”. Candela is denoted by symbol ‘cd’. Some other units are lux, lumen, etc.
The SI unit of Distance is “Meter”. Distance also measures in mm, cm, km, yard, inch, foot, feet, etc.
The SI unit of temperature is “Kelvin”, expressed as the word “K”.Temperature 0 K is known as “absolute zero.”
We use two types of scale in measuring temperature that is –
1.Relative scales [Fahrenheit (°F) and Celsius (°C)]
2. Absolute scales [Rankine (°R) and Kelvin (K)].