Measurement Error analysis
- Error analysis is the difference between true value and desired value .
- It can be expressed as absolute or parentage of errors.
The difference between the actual value of variables and measured value known as absolute error.
Ee = Vt – Vm
Vt – true or actual value
Vm – measured value
% E = absolute value/ true value * 100
Error contains two terms :
1. Accuracy – it is define as the closeness of the measured value to the actual value. It can be expressed as either percentage of scale or range of percentage.
2. Precision – it is a measurement of the reproducibility of the measurements. It is a measure of the degree of agreement within a group of measurement.
Types of errors
- Static error – it is a numerical difference between actual value and measured value.
- gross error – when human did the mistake during the taking reading of measurement and observations is called gross error.
- random error – this error treated as the mathematically error. And its occur because of unknowns causes and are normally follow the law of probability and small.
- systematic error – the error in occur due to when instrument is defective or any internal problem or due to worn out parts of the instruments or due to environmental conditions.
In order to understand the concept of systematic errors, let us classify the errors as:
- Instrumental Errors
- Environmental Errors
- Observational Errors
- Instrumental error: instrumental errors occur due to wrong design of the instruments. This errors may occur due to friction or hysteresis . These errors include loading effect and misuse of the instruments.
- Environmental error: The environmental errors occur due to some external conditions of the instrument. External conditions mainly include wind pressure, humidity, temperature, moisture or due to magnetic fields. In order to reduce the environmental errors Try to maintain the humidity and temperature constant in the laboratory by making some arrangements.
- Observational error: these types of errors occurs due to wrong reading in the instruments or observations particularly in case of whatthour meter reading. The wrong observations may be due to parallax. by using high accurate instruments we can reduced parallax. mirror scale is provided with the meter.
Causes of errors
There are different different sources or causes of errors listed below.
1. Poor maintenance of equipment
2. Poor design of equipment
3. Lack of knowledge of design and process of parameters.
4. Change in process parameters irregularities.
5. Miss operation by human.