In this topic, you study the Types of Errors in Measurement.
No measurement can be done with perfect accuracy however, errors may be reduced to some extent and effects may be made to get maximum accurate results. Here are given types of errors, their source and elimination techniques.
TYPES OF ERRORS
Errors may be of the following types :
- Environmental Errors : Errors are caused due to the surroundings of the instrument, e.g., ambient temperature, humidity, pressure, dust, vibrations etc. The most important factor which effects the reading of the instrument is the presence of electrical/magnetic fields in the surroundings for this purpose, the instruments are screened by using a soft iron cover (Fig. 1.8). Since soft iron has high permeability. the external magnetic fields will be bypassed through the iron cover and the instrument (which have steel parts) are protected from external magnetic disturbances. This is called magnetic shielding.
Fig. 1.8. Magnetic shielding.
2. Observational Errors : While reading an instrument the observer may himself add an error. The most important is the error due to parallex. To reduce this error, the meter is provided with a mirrored scale. While reading, the line of vision ofthe observer, the pointer and its image in the mirror all the three should be in line. See Fig. 1.9 (a). We can reduce this error also having the pointer, the scale and the vision in the same plane. See Fig. 1.9 (b). For this purpose, quality instruments are provided with a mirror on the dial.
Fig. 1.9. Parallex