Dear students, welcome to my youtube channel RPA square and this is fifth lecture of electrical measurements and instrumentation subject and in this lecture we will study about measurement standards and their classification as well as measuring instruments or we can say that types of instruments. Let's start. First of all what is measurement standard?
Standard is a physical representation of a unit of measurement and it is classified into various types like international standards, primary standards, secondary standards and Working standards now international standards international standards is a unit of measurement which are using in the present day technology and scientific methods Now primary standards primary standards are useful in national standards laboratories in all over world now secondary standards These are used in the industrial measurement laboratories Working standards these standards are used in the general laboratory instruments for their accuracy and performance Now measuring instruments or types of instruments First of all, what is measuring instruments? An instrument is a device in which we can determine the magnitude or value of the quantity to be measured. Means that instrument is a kind of device by which we can measure magnitude or value of any quantity. And measuring quantities can be either voltage or current or power or energy etc.
Now types of instruments. Instruments are classified into two categories, absolute and secondary instruments. Now absolute instruments.
An absolute instrument determines the magnitude of the quantity to be measured. And a secondary instrument determines the magnitude of the quantity to be measured. in terms of instrument's parameter. Means that these type of instruments can determine the magnitude of any quantity which we have to measure in terms of instrument parameter. And in this instrument measuring value is varies each time.
Means that every time reading value comes different. So we have to calculate the magnitude of the measuring quantity analytically which is time consuming. That's why these type of instruments suitable only for laboratory use.
Tangent galvanometer is an example of absolute instrument. Secondary instrument. Secondary instrument determine the value of the quantity to be measured directly.
And these type of instruments can calibrate by comparing with another secondary instruments like voltmeter, ammeter and wattmeter etc. So, practically secondary instruments are suitable for measurement like these all. And secondary instruments are divided into three types indicating instruments, recording instruments and integrating instruments. Now, we will study about these all one by one. First of all, indicating instruments.
Indicating instruments are those instruments which indicate the magnitude of a quantity being measured. means that indicating instruments indicate reading value and show it and in this dial or we can say that pointer is used for measurement of unknown quantity and the example of indicating instruments are voltmeter, ammeter, wattmeter, power factor meter etc now recording instruments recording instruments give a continuous record of a quantity being measured over a specified period means that recording instruments give record of measuring quantity continuously and in this recording instruments pen is used to record the value of measuring quantities on a seed paper and seed paper can be fixed or moving and the example of recording instruments are graph memory etc now integrating instruments integrating instruments totalizes events over a specified period of time means that integrating instruments integrates all the events and we will get in the output of this type of instrument product of time and any electrical quantity and the example of integrating instruments are energy meter ampere hour meter etc okay dear students if you have any question or any doubt you can ask your question or doubts by commenting on this video thank you