What is Calibration? According to metrology, calibration can be defined as process of identifying and removing the errors from instrument that are caused due to constant temperature difference, inappropriate usage of instrument, wear and tear of the instrument.
Why calibration is needed? Every instrument after doing certain number of experiments, they will undergo some errors and these errors can be removed by using certain standard known instrumental values and those instruments are called Calibrators and that process is known as “Calibration”.
Fig.1 graph on after and before calibrating an instrument
On the above given graph, red dotted line shows readings of the instrument before calibration and green line shows measurements of instrument after doing calibration. These two lines are compared with the actual or standard values of tested piece and green line is very nearer to the actual line. So that we can say by calibrating an instrument can increase precision and accuracy of the measuring instrument.
Calibration is mainly used to obtain these factors Accuracy: It is process of obtaining measured values nearer to the actual values. Precise or reproducibility: It is a process of obtaining values that are nearly equal to previously measured value.
Factors affecting calibration Ambient temperature: The effect of temperature and pressure will always be there on instrument as experiment will be carried out in the atmosphere. But by performing calibration in that affects causing atmosphere can reduce effects. The temperature at which experiment is carried out will have huge effect on instrument so one need to do calibration of that instrument frequently in order to reduce errors in machining.
Human errors: Inappropriate usage of instrument may lead to arise errors in the instrument which will lead to do calibration to the instrument. So, by appropriate usage gives best readings for experiment.
What kind of equipment can be calibrated? Accelerometer, Load cells, Force gauges, Micrometer, Vernier, Height gauges, Scales, Torque wrenches and Screwdriver.
Process for Calibration:
It may vary from instrument to instrument depending on its operation and standards that are followed by the working institution. They are
Clean the instrument before performing calibration. Take a known standard value of the calibrator and note down reading for three consecutive. Take average of those three readings and draw graph using those known standard and experimental values. Compare two graphs and the difference between these two values gives deviation from standard value.
What is Calibration of equipment?
Calibration of equipment needs to be carried out on a regular basis. This is because instruments tend to deviate owing to hard operating conditions, mechanical shocks or exposure to extreme temperature or pressure. Frequency of calibration would depend on the tolerance level. When the objective of the measurement is critical calibration would need to be carried out more frequently and with great accuracy.
Benefits of calibration: Accuracy in experimental readings will increased. Precision or reproducibility of an instrument will also be maximized. The cost spent on buying new instruments will be minimized there by increasing the profit for the industry.