1) Gross Errors -These errors occur due to human mistakes while taking reading, handling instrument, incorrect setting or adjustment and improper used of instrument.
The complete elimination of gross errors is not possible but we can minimize it. These errors may be avoided by taking reading and recording it carefully.
2) Systematic Errors –These errors occur due to shortcoming of the instrument, such as defective or worn part or aging or effect of environment on the instrument.
These errors are further classified as –
i) Instrumental errors – These errors arise due to inherent shortcoming of instrument, misuse of instrument, loading effect of instrument.
These errors can be removed by selecting suitable instrument for particular application.
ii) Environmental error- These errors occur due to external condition to the measuring instrument, such as temperature, pressure, humidity, dust and external magnetic field.
These errors can be avoided by keepingcondition constant with the help of air conditioning, temperatures control, enclosure etc.
iii) Observational error – observational error introduced by observer. The most common error is the parallax error introduced in reading a meter scale.
3) Random Errors – These errors are due to unknown causes. These errors remain since the systematic and gross error are removed. Generally these errors are very small.