PPT: Measuring Instruments | Basic Electrical Technology - Electrical Engineering (EE) PDF Download

 Page 1


MEASURING INSTRUMENTS
What is meant by measurement?
• Types of instruments
1. Absolute instruments
2. Secondary instruments
indicating integrating recording
Page 2


MEASURING INSTRUMENTS
What is meant by measurement?
• Types of instruments
1. Absolute instruments
2. Secondary instruments
indicating integrating recording
• Absolute instrument:
Page 3


MEASURING INSTRUMENTS
What is meant by measurement?
• Types of instruments
1. Absolute instruments
2. Secondary instruments
indicating integrating recording
• Absolute instrument:
• Indicationg instruments:
Indicating instruments indicate the value of the 
electrical quantity to be measured generally by the 
deflection of the pointer on the calibrated scale.
e.g.- voltmeter, ammeter, wattmeter
• Essential system of Indicating Instruments:
1. A deflection system
2. A controlling system
3. A damping system
Page 4


MEASURING INSTRUMENTS
What is meant by measurement?
• Types of instruments
1. Absolute instruments
2. Secondary instruments
indicating integrating recording
• Absolute instrument:
• Indicationg instruments:
Indicating instruments indicate the value of the 
electrical quantity to be measured generally by the 
deflection of the pointer on the calibrated scale.
e.g.- voltmeter, ammeter, wattmeter
• Essential system of Indicating Instruments:
1. A deflection system
2. A controlling system
3. A damping system
Deflection system:
It is that part of the instrument mechanism which 
utilize some physical effect of electric current or voltage to 
produce a mechanical force. This deflection or force causes 
the system along with the pointer attached to it to move 
from it’s zero position.
The magnetude of the deflection force(deflection of 
pointer) depents on the value of electrical quantity to be 
measured.
Page 5


MEASURING INSTRUMENTS
What is meant by measurement?
• Types of instruments
1. Absolute instruments
2. Secondary instruments
indicating integrating recording
• Absolute instrument:
• Indicationg instruments:
Indicating instruments indicate the value of the 
electrical quantity to be measured generally by the 
deflection of the pointer on the calibrated scale.
e.g.- voltmeter, ammeter, wattmeter
• Essential system of Indicating Instruments:
1. A deflection system
2. A controlling system
3. A damping system
Deflection system:
It is that part of the instrument mechanism which 
utilize some physical effect of electric current or voltage to 
produce a mechanical force. This deflection or force causes 
the system along with the pointer attached to it to move 
from it’s zero position.
The magnetude of the deflection force(deflection of 
pointer) depents on the value of electrical quantity to be 
measured.
Control systems:
It is that part of the instrument which brings into 
play a force called controlling force. This force opposes the 
deflection force and increases with the increase in the 
deflection of the moving system, to limit its movement.
The pointer is brought to rest at a position where the 
two opposing forces i.e. deflection and controlling forces 
are equal.
Types of control system:
1. Spring control
2. Gravity control