Error in Measurements

Error

The error is the difference between the actual value of a quantity and the value obtained by measurement. Every measurement has along with it a level of uncertainty which is known as an error.

 No measurement can be done with perfect accuracy and precise but it is important to find out what an accuracy actually is and how different error have inter to the measurements so the study of error is the first step in finding the way to reduce them.

Type of error
1) Gross error
2) Sysematic error
3) Random error

Gross error

It covers mainly human mistakes in reading instrument, recording and calculating measurement results responsibility of the mistakes normally lies with the experimenter

The experimenter may grossly miss-read the scale.

For example -experimenter read the temperature add 40 degree Celsius instead of 50-degree celsius experimenter may transpose the reading by recording how as long as a human being are involved some gross error will definitely be committed also complete although complete examination of gross error is possibly impossible so one should try to anticipate and correct them.

some gross error easily detected while others may be very difficult to detect.

Precaution
1) great care should be taken in reading and recording the data
2) two three or more reading should be taken for quantity under a mean measure

Systematic error

It is further divided into three categories
1) instrumental error
2) environmental error
3) observational error

1) Instrumental error

This error arises due to-
a) Inherent suit coming-

These errors are inherent in the instrument because of their mechanical structure they may be due to construction calibration or operation of the instrument.
this error may cause an instrument to read too low too high
Avoided by-
the instrument may be recalibrated carefully.
correction factors should be applied after determining the instrumental error.
Error measurement must be carefully planned.

b) Misuse of instrument

Too often the error causing in measurement are due to the fault of the operator than that of the instrument is used in and an unintelligent way my way give an error in the result.

c) Loading effect

One of the most common errors committed by beginners is the improper use of an instrument or measurement works.
E.g.- well-calibrated voltmeter may give a misleading voltage rating when connected across a high resistance circuit however some voltmeter when connected in a low resistance circuit. it gives a more precise reading.

2) Environmental error

This error due to the condition of external to the measuring device that is conditions conditions surrounding to the instrument this error may be of temperature, pressure or humidity, variation in external magnetic field etc

3) Observational error

This error caused due to data is not taken in the right way for example. Of voltmeter rest slightly above the surface of a screen and error of parallax will be there unless the line of vision of observer is exactly above the pointer
To minimise the parallax error highly accurate metres are provided with mirror scale and light should be available for reading purpose.

Random error

The happenings of disturbances about which we are unaware or lumped are called random error. hence error caused by these happening at any instant.