Errors in Measurement

Errors in Measurement Definition

Errors in measurement are defined as the differences between measured values and true values.

Static Error Formula

Static error is calculated using the formula dA = Am – At, where dA is the error, Am is the measured value, and At is the true value.

Limiting Errors

The concept of guarantee errors can be cleared if we study this kind of error by considering one example. Suppose there is a manufacturer who manufactures an ammeter, now he should promise or declare that the error in the ammeter that he is selling is not greater than the limit he sets. This limit of error is known as limiting errors or guarantee error.

Gross Errors

This category of errors includes all the human mistakes while reading, recording and the readings. Mistakes in calculating the errors also come under this category. For example while taking the reading from the meter of the instrument he may read 21 as 31. All these types of error are come under this category. Gross errors can be avoided by using two suitable measures and they are written below:

A proper care should be taken in reading, recording the data. Also calculation of error should be done accurately.By increasing the number of experimenters we can reduce the gross errors. If each experimenter takes different reading at different points, then by taking average of more readings we can reduce the gross errors.

Systematic Errors

Systematic errors are consistent inaccuracies due to faulty instruments, environmental conditions, or observational mistakes.

Instrumental Errors

These errors may be due to wrong construction, calibration of the measuring instruments. These types of error may arise due to friction or may be due to hysteresis. These types of errors also include the loading effect and misuse of the instruments. Misuse of the instruments results in the failure to the zero adjustment of the instruments. In order to minimize the gross errors in measurement various correction factors must be applied and in extreme condition instrument must be re-calibrated carefully.

Environmental Errors

This type of error arises due to conditions external to the instrument. External condition includes temperature, pressure, humidity or it may include external magnetic field. Following are the steps that one must follow in order to minimize the environmental errors:

Try to maintain the temperature and humidity of the laboratory constant by making some arrangements.Ensure that there should not be any external magnetic or electrostatic field around the instrument.

Observational Errors

As the name suggests these types of errors are due to wrong observations. The wrong observations may be due to PARALLAX. In order to minimize the PARALLAX error highly accurate meters are required, provided with mirrored scales.

Random Errors

After calculating all systematic errors, it is found that there are still some errors in measurement are left. These errors are known as random errors. Some of the reasons of the appearance of these errors are known but still some reasons are unknown. Hence we cannot fully eliminate these kinds of error.