1. Static error : The error which occurs in stationary condition is called as static error. These are classified as:
i. Gross errors: the errors which occur due to human mistakes while taking reading, handling instrument incorrect setting or adjustment and improper use of instrument are known as gross errors.
ii. 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.
Instrumental error: the errors which arise due to inherent shortcoming of instrument, misuse of instrument, loading effect of instrument are called as instrumental error.
Environmental error: these errors occur due to external condition to the measuring instrument, such as temperature, pressure, humidity, dust and external magnetic field.
Observation error: these are introduced by the observer. the most common error is the parallex error introduced in reading a meter scale.
iii. Random error: these errors are due to unknown causes, these error remain since the systematic and gross error are removed,
2. Dynamic error: the difference between true value of a quantity changing with time and value indicated by instrument if no static error is assumed is called as dynamic error.