Error in Measurement and Analysis | Electrical and Electronic Measurements - Electrical Engineering (EE) PDF Download

 Page 1


ERRORS IN 
MEASUREMENT AND 
ANALYSIS 
Page 2


ERRORS IN 
MEASUREMENT AND 
ANALYSIS 
No Measurement is Accurate! 
is Accurate! 
No Measurement 
 Errors occur 
because of: 
Errors occur because of: 
1. Parallax error error (incorrectly (incorrectly sighting sighting the the measurement). 
measurement). 
1. Parallax 
2. Calibration error (if (if the the scale scale is is not not accurately accurately drawn). 
drawn). 
2. Calibration error 
3. Zero error (if (if the the device device doesn’t have doesn’t have a a zero or zero or isn’t 
isn’t 
3. Zero error 
correctly set to zero). 
correctly set to zero). 
4. Damage (if (if the the device device is is damaged or damaged or faulty). 
faulty). 
4. Damage 
5. Limit of of reading reading of of the the measurement measurement device device (the 
(the 
measurement can only be as accurate as the smallest unit 
5. Limit 
measurement can only be as accurate as the smallest unit 
of measurement measurement of of the the device). 
device). 
of 
Page 3


ERRORS IN 
MEASUREMENT AND 
ANALYSIS 
No Measurement is Accurate! 
is Accurate! 
No Measurement 
 Errors occur 
because of: 
Errors occur because of: 
1. Parallax error error (incorrectly (incorrectly sighting sighting the the measurement). 
measurement). 
1. Parallax 
2. Calibration error (if (if the the scale scale is is not not accurately accurately drawn). 
drawn). 
2. Calibration error 
3. Zero error (if (if the the device device doesn’t have doesn’t have a a zero or zero or isn’t 
isn’t 
3. Zero error 
correctly set to zero). 
correctly set to zero). 
4. Damage (if (if the the device device is is damaged or damaged or faulty). 
faulty). 
4. Damage 
5. Limit of of reading reading of of the the measurement measurement device device (the 
(the 
measurement can only be as accurate as the smallest unit 
5. Limit 
measurement can only be as accurate as the smallest unit 
of measurement measurement of of the the device). 
device). 
of 
Definitions 
Definitions 
1. Limit of Reading 
1. Limit of Reading : is is the the smallest smallest unit unit of 
of 
measurement on the measuring instrument. 
: 
measurement on the measuring instrument. 
2. The Greatest Possible Error 
2. The Greatest Possible Error 
(also called the 
(also called the 
absolute error): is equal to half the the limit limit of 
of 
absolute error): is equal to half 
reading. 
reading. 
3. The Upper and Lower Limits 
3. The Upper and Lower Limits : are the are the smallest 
smallest 
and largest value between which a measurement 
: 
and largest value between which a measurement 
can lie. 
can lie. 
Page 4


ERRORS IN 
MEASUREMENT AND 
ANALYSIS 
No Measurement is Accurate! 
is Accurate! 
No Measurement 
 Errors occur 
because of: 
Errors occur because of: 
1. Parallax error error (incorrectly (incorrectly sighting sighting the the measurement). 
measurement). 
1. Parallax 
2. Calibration error (if (if the the scale scale is is not not accurately accurately drawn). 
drawn). 
2. Calibration error 
3. Zero error (if (if the the device device doesn’t have doesn’t have a a zero or zero or isn’t 
isn’t 
3. Zero error 
correctly set to zero). 
correctly set to zero). 
4. Damage (if (if the the device device is is damaged or damaged or faulty). 
faulty). 
4. Damage 
5. Limit of of reading reading of of the the measurement measurement device device (the 
(the 
measurement can only be as accurate as the smallest unit 
5. Limit 
measurement can only be as accurate as the smallest unit 
of measurement measurement of of the the device). 
device). 
of 
Definitions 
Definitions 
1. Limit of Reading 
1. Limit of Reading : is is the the smallest smallest unit unit of 
of 
measurement on the measuring instrument. 
: 
measurement on the measuring instrument. 
2. The Greatest Possible Error 
2. The Greatest Possible Error 
(also called the 
(also called the 
absolute error): is equal to half the the limit limit of 
of 
absolute error): is equal to half 
reading. 
reading. 
3. The Upper and Lower Limits 
3. The Upper and Lower Limits : are the are the smallest 
smallest 
and largest value between which a measurement 
: 
and largest value between which a measurement 
can lie. 
can lie. 
Types of Errors 
 Basically Three types of errors are studied:-            
 1. Gross Errors 
 2. Systematic Errors 
 3. Random Errors 
Page 5


ERRORS IN 
MEASUREMENT AND 
ANALYSIS 
No Measurement is Accurate! 
is Accurate! 
No Measurement 
 Errors occur 
because of: 
Errors occur because of: 
1. Parallax error error (incorrectly (incorrectly sighting sighting the the measurement). 
measurement). 
1. Parallax 
2. Calibration error (if (if the the scale scale is is not not accurately accurately drawn). 
drawn). 
2. Calibration error 
3. Zero error (if (if the the device device doesn’t have doesn’t have a a zero or zero or isn’t 
isn’t 
3. Zero error 
correctly set to zero). 
correctly set to zero). 
4. Damage (if (if the the device device is is damaged or damaged or faulty). 
faulty). 
4. Damage 
5. Limit of of reading reading of of the the measurement measurement device device (the 
(the 
measurement can only be as accurate as the smallest unit 
5. Limit 
measurement can only be as accurate as the smallest unit 
of measurement measurement of of the the device). 
device). 
of 
Definitions 
Definitions 
1. Limit of Reading 
1. Limit of Reading : is is the the smallest smallest unit unit of 
of 
measurement on the measuring instrument. 
: 
measurement on the measuring instrument. 
2. The Greatest Possible Error 
2. The Greatest Possible Error 
(also called the 
(also called the 
absolute error): is equal to half the the limit limit of 
of 
absolute error): is equal to half 
reading. 
reading. 
3. The Upper and Lower Limits 
3. The Upper and Lower Limits : are the are the smallest 
smallest 
and largest value between which a measurement 
: 
and largest value between which a measurement 
can lie. 
can lie. 
Types of Errors 
 Basically Three types of errors are studied:-            
 1. Gross Errors 
 2. Systematic Errors 
 3. Random Errors 
Gross Errors 
   Gross Errors mainly covers the human mistakes in 
reading  instruments  and  recording  and  calculating 
measurement results. 
   Example:- Due to oversight, The read of Temperature 
as 31.5   while the actual reading may be 21.5  .