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CALIBRATION AND ITS IMPACT TO MODERN ENGINEERING

 

Calibration is the process of setting, measuring, correcting, or adjusting any measuring or controlling instrument against deviation from the known standard. The calibration of all instrument is very important. It is the only known way to check the instrument against a known standard and subsequently reduce error in accuracy.

Calibration is not just to check the instrument, it has to do with resetting it to the default values which stands as the standard set by the manufacturer. Any instrument that falls outside its standard setting will become a source of error to the user and could lead to heavy loss and repeated mistakes.

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The best place calibration is very important is the measuring instruments. During measurement, each measurement can be affected by the absolute or comparative method. In addition, any measurement can be conducted by either the contact or the non-contact method.

In the absolute method of measurement, the dimension is obtained directly by instrument indication. The comparative method gives only a deviation from the size of a set standard used to zero a measuring instrument. Instruments for comparative measurements, as a rule, offer higher accuracy of measurement due to the possibility of reading smaller size deviation of the instrument scale which is more accurately made and usually has a certain magnification.

Contact measurement involves the direct engagement of the instrument measuring faces with the surface of the part being measured. Non-contact measurement features the absence of any physical contact of the instrument with the measured part such as measuring with a microscope or optical projector.

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Therefore, calibration procedures involve a comparison of the particular instrument with either:

A primary standard or a secondary standard with higher accuracy on the instrument to be calibrated or a known input source. For example, a flowmeter might be calibrated by:

Comparing it with a standard flow measurement facility of the National Bureau of standards.

Comparing it with another flowmeter of known accuracy or

Direct calibration with a primary measurement such as weighing a certain amount of water in a tank and recording the elapsed for this quantity to flow through the meter.

The keyword when it comes to calibration is ‘accuracy’, that means the accuracy of the meter must be specified by a reputable source.

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The importance of calibration cannot be overemphasized because it is calibration which firmly establishes the accuracy of the instruments. Rather than accept the reading of an instrument, it is usually best to make at least a simple calibration check to be sure of the validity of the measurements. Not even the manufacturer’s specifications or calibrations can always be taken at face value. Though most instruments manufacturers are reliable, some are not.

A voltmeter, for instance, carries no voltage standard of its own. As time passes, heat and atmospheric conditions cause its electronic components to age and change their electrical properties slightly. As a result, the voltage readings become less and less accurate, and it is impossible to predict whether they are getting too high or too low. In fact, there is no way to tell if the calibration is necessary until it is actually performed.

Nature has the habit of making changes on all physical objects, including measuring instruments and humans beings.

Electronic devices are particularly susceptible to these changes and time should always be taken to go through the calibration procedures when accuracy is important. Mechanical devices are susceptible to friction, wear and sometimes fatigue. Mechanical instruments that depend on weights are subject to weight-gains through oxidation. Relatively minor temperature fluctuations may affect distance measuring equipment.

Optical instrument is affected by temperature, mechanical vibration, and occasionally humidity. It should be noted that these changes are taking place to some extent, regardless of the care taken to prevent them. And the only way to place any confidence in the result of a measurement is to make sure that the instrument has been recently and properly calibrated against a reliable standard.

For instance, when a thermometer is manufactured, it is calibrated against a standard, sometimes by placing it in a bath known to be 0oC, then adjusting the scale so it actually reads 0oC. After that, every time we use the thermometer, we are actually comparing our unknown temperature with the temperature of the manufacturer’s standard.

 

 

 

 

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Originally posted 2018-12-05 02:05:13.

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