Direct and Indirect Measurements

Here we will be discussing some basics of the direct and indirect measurements.

1. Firstly we will explain what is a direct measurement?

To understand this question the basic principle in all direct methods the unknown quantity is compared with known standard quantity.

• This unknown quantity is also called Measurand.

                            Examples of some direct measurement:              1) Length:          

  

SESSION -1

First we need to know the purpose of measurement systems.

The main purpose of the measurement system is to present an observer with a numerical value so that the observer can understand easily.

and for a better understanding today we use the digital displays because they provide with clear understanding and user friendly operations along with the main advantage being the over ranging facility.




Now we will present you with a very basic block diagram to understand the root measuring  devices components.

BASIC SYSTEM DIAGRAM

              Error= true value- measured value.

Basic Block Diagram

SYLLABUS FOR PREPARATION OF SUBJECT ELECTRONICS MEASUREMENT AND INSTRUMENT (E.M.I)

 1. Basics and Measurement System

 2. Direct and Indirect methods

 3. Error analysis

 4. Basic Analog Instruments:

      a) PMMC (Permanent Moving Magnet Coil )

      b) MI (Moving Iron)
  
      c) EMMC Type

      d) Thermal Instruments
    
      e) ESV Type

      f) Rectifiers
 5. Measurement of Resistance
   
     a) V-A Method

     b) A-V Method

     c) D.C. BRIDGES

• Wheatstone Bridge
• Kelvin Double Bridge         

  6. Measurement of Inductance/Measurement of Capacitance/Mutual Inductance

• AC Bridges

 7. Measurement of Power
   
    a) D.C. Power Measurement
     

• V-A Method
• A-V Method

    b) A.C. Power Measurement

• Single Phase Power
• Three Phase Power

  8. Reactive Power Measurement

  9. Measurement of Energy

 10. Potentiometer

 11. Overview of   Instrumentation transformer/Current transformer/ Potential transformer

 12. Electronic Devices
   

• Q Meter
• C.R.O
• D.V.M (Digital Voltmeter)

 13. Transducers

• Primary
• Secondary
• Electrical