Sources of Errors.pptx

This PPT explains sources of errors

1. SOURCES OF ERRORS II PHYSICS – 04.03.2022 Dr.R.Hepzi Pramila Devamani, Assistant Professor of Physics, V.V.Vanniaperumal College for Women, Virudhunagar.

2. Sources of Errors In the process of measurement, the errors are bound to occur. If the sources of errors are known, then the efforts can be made to reduce the errors and partly to eliminate them. The various possible sources of errors are, Faculty design of the instrument which directly leads to the serious measurement errors. Due to insufficient knowledge of the quantity to be measured and design conditions can cause errors. For the instruments frequent maintenance is necessary. If such maintenance is not done then the errors may occur. If there are irregularities in quantity to be measured or sudden changes in the parameter to be measured then errors may exist. The unskilled operator of the instrument can cause serious errors. The certain limitations while designing the instrument can cause errors. Loading effect i.e. improper way of using the instrument ca cause the errors. The effects of environmental conditions, temperature changes, stray capacitances also can cause the errors. Proper care taken considering the sources of errors can help to reduce the percentage of errors and to improve the accuracy of measurement.

3. Types of Errors The static error is defined as the difference between the true value of the variable and the value indicated by the instrument. The static error may arise due to number of reasons. The static errors are classified as Gross errors Systematic errors Random Errors

4. Gross Errors The gross errors mainly occur due to carelessness or lack of experience of a human being. These cover human mistakes in readings, recordings and calculating results. These errors also occur due to incorrect adjustments of instruments. These errors can not be treated mathematically. These errors are also called personal errors. Some gross errors are easily detected while others are very difficult to detect. The complete elimination of gross errors is not possible but one can minimize them by the following ways. Taking great care while taking the reading, recording the reading and calculating he result. Without depending on only one reading. At least three or even more readings must be taken and preferably by different persons. The readings must be taken preferably under the conditions in which the instruments are switched on and off.

5. Systematic Errors The systematic errors are mainly resulting due to the shortcomings of the instruments and the characteristics of the material used in the instrument such as defective or wrong parts, ageing effects, environmental effects etc. A constant uniform deviation of the operation of an instrument is known systematic error. There are three types of systematic errors as Instrumental errors Environmental errors Observational errors

6. Instrumental Errors These errors can be mainly due to the following three reasons A)Shortcomings of Instruments These are because of the mechanical structure of the instruments. For example friction in he bearings of various moving parts, irregular spring tensions, reduction in tension due to improper handling, hysteresis, gear backlash, stretching of spring, variation in air gap etc. These errors can be avoided by the following methods. Selecting a proper instrument and planning of proper procedure for measurement. Recognizing the effect of such errors and applying the proper correction factors. Calibrating the instrument carefully against a standard. B) Misuse of Instruments A good instrument if used in abnormal way gives misleading results. Poor initial Adjustments, improper zero setting, using leads of high resistance etc are examples of misusing a good instrument. Such things do not cause permanent damage to the instruments but definitely cause serious errors.

7. Instrumental Errors C) Loading Effects Loading effect due to improper way of using the instrument cause serious errors. The best example of such loading effect error is connecting a well calibrated voltmeter across the two points of high resistance circuit. The same voltmeter connected in a low resistance circuit gives accurate reading. Thus the errors due to the loading effect can be avoided by using an instrument intelligently and correctly.

8. Environmental Errors These errors are due to the conditions external to the measuring instrument. The various factors resulting these environmental errors are temperature changes, pressure changes, thermal emf , stray capacitance, cross capacitance, effect of external fields, ageing of equipment and frequency sensitivity of an instrument. The various method which can be used to reduce these errors are Using proper correction factors and using the information supplied by the manufacturer of the instrument. Using the arrangements which will keep the surrounding conditions constant. This includes the use of air conditioning , temperature control enclosures. Reducing the effect of dust and humidity The effects of external fields can be minimized by using the magnetic or electrostatic shields and screens. Using the equipment which is immune to environmental effects.