Define Accuracy, Precision, Reliability, Calibration,Hysteresis?

What is Accuracy?

Accuracy is the closeness with which an instrument reading approaches the true value of the variable being measured. The accuracy of a complete system is depended upon the individual accuracy of the primary sensing element, secondary element and the manipulation device. It is influenced by static error, dynamic error, drift, reproducible and non-linearity. 

Accuracy of a measurement means conformity to true value. 

What is Precision?

The difference between two successive or consecutive readings measured by instrumentation system is known as precision. High precision means a tight cluster of repeated results while low precision indicates a board scattering of results.

define precision

What is Reliability?

It is defined as the probability that an instrument will perform its assigned function for a given specific period of time under given condition is Known as Reliability.

Reliability

What is Calibration?

Calibration is an essential part of industrial measurement and control. All the static performance characteristic are obtained in one form or other by a process called statics calibration. 

Considerations at the time of instrument calibration:

1. Calibration of the instrument is carried out with the instrument in the same position (upright, horizontal etc. ) and is subjected to same temperature and other environmental condition under it is to operate. 

2. The instrument is calibrated with values of the measurand impressed in both increasing and decreasing order. 

Calibration depends upon following factors:

1. Accuracy desired. 

2. Range of instrument. 

3. Sensitivity desired. 

4. Application of instrument. 

5. Environmental conditions.

Advantages of calibration

1. faster and easier to use.
2. Usually no measurement correction.
3. Generally less expensive.

Disadvantages of calibration

1. Must be periodically re calibrated by a standard traceable to nation standard traceable to nation standard.
2. Pressure measurements cannot be reduced to measurements of mass, length or temperature.

Calibration

What is Hysteresis?

Hysteresis is a phenomenon which gives different output effects when loading and unloading weather it is mechanical system is known as Hysteresis.

Hysteresis