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Introduction to Calibration

 

What is
calibration?

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Calibration
is the most common word used in the measurement technology. In simple word
calibration means checking the reading of given object over and over again
until it is precise or accurate.

 

Definition
of Calibration:

Definition of calibration by the International Bureau of Weights and Measures (BIPM) is the
following: “Operation that, under specified conditions, in a first step,
establishes a relation between the quantity values with measurement
uncertainties provided by measurement standards and corresponding indications
with associated measurement uncertainties (of the calibrated instrument or
secondary standard) and, in a second step, uses this information to establish a
relation for obtaining a measurement result from an indication.”

Accuracy,
Precision, Calibration are all term that we encounter frequently in our day to
day life and certainly in specification of testing equipment. The illustrations
below show the inter-relationship between these terms.

 

 

Precision
means that you can hit the same point time and again within certain error
limits. But, as the target illustrates, you can be precise without ‘hitting’
the bullseye.

Accuracy
is precision with calibration. This means that you not only repeat time and
again within prescribed error limits but also that you hit what you are aiming
for.

Precision,
accuracy, calibration; similar terms but with very dissimilar meanings.
Accuracy is difficult without good precision. Precision, however, does not
ensure accuracy. Precision with calibration results in accuracy.

 

Why calibration
is important?

The
accuracy of any measuring device doesn’t remain same over long period of time,
it varies due to many reason like wear and tear, electrical shock etc. That is
where calibration play vital role. Basically, calibration compare our reading
or measurement to the standard measurement. Thus, calibration improves the
accuracy of the measuring device. Accurate measuring device improve the product
quality.

It
is important that the device or equipment which we use to measure the
quantities are accurate. The equipment can be related to any field from
automation industry, photography, mechanical industry to even medical field.
This equipment need to be verified that they give correct data.

 

Calibration
system is necessary in any company that uses measuring and testing equipment to
gain the assurance that the testing equipment is accurate at the time of
calibration.

Calibration
standard should define frequencies for calibration of all measuring equipment,
work instrument for method of calibration, and procedures for adjusting calibration
frequencies based on the degree of usage of equipment and the result of
calibration. Calibration system should also identify source of calibration,
environmental condition, the action to be taken to correct the equipment that
is found out of calibration. If calibration stickers are used, the information
on the sticker should specify when the equipment was calibrated, who perform
the calibration, and when the next calibration should performed.

 

Main
reasons to have equipment calibrated:

·        
To
make sure that reading is consistence with other measurement.

·        
Determine
accuracy with equipment’s reading.

·        
Establish
reliability or trust on equipment.

 

Instrument
which are calibrated keeps the process safe. While measuring any thing we have
to make sure that measured parameter maintained product safety. This could
cause safety hazard if there are not. For example, if certain stored food is
about expire on specific temperature, but thermometer in refrigerator is not
reporting that temperature then food can get spoiled and the person who eat
that can get infected by it. This could happen if reading is not accurate.

Machine
calibration can help to reduce the costs from manufacturing errors. In
manufacturing industry any minor defect in the process can cost lot of money.
Any small or minute error of inches in work piece can cause improper position
for further activity on any machine and it is not monitored properly then again
that specific workpiece will need some modification or to replace it and it can
cause lot of money.

To
reduce this manufacturing defects from occurring, the sensors which monitor
this process should be very accurate. Calibrating gauges and instrumentation
will reduce the possibility of production defects.

Different
types of calibration:

·        
Pressure
calibration

This
is widely used calibration process in which gas and hydraulic pressure are
measured across the broad spectrum.

Example
of pressure equipment include: Barometer, Digital pressure gauges,
Transmitters, Analogue pressure gauges etc.

·        
Electrical
calibration

This
type of calibration process is used to measure current frequency, voltage and
resistance.

Examples:
Multi-meter, Loop tester, RCD, Data logger, etc.

·        
Mechanical
calibration

In
this calibration process mass, dimension, force, torque and vibration element
are measured.

Examples:
Weight and mass sets, Micrometers, screwdrivers, accelerometer etc.

·        
Temperature
and humidity calibration

A
temperature calibration takes place in controlled environment. A number of
different types of equipment can be tested using temperature calibration,
includes: thermometer, weather station, furnace, dial thermometer, etc.

 

 

 

 

Reference:

https://en.wikipedia.org/wiki/Calibration

http://www.instron.us/-/media/literature-library/products/2006/04/definition-accuracy-precision-calibration.pdf?la=en

Why Calibration of Your Measuring Instruments is Important

The
Quality Technician’s Handbook by Gary K. Griffith

https://www.measurement.govt.nz/services/temperature-and-humidity/humidity-calibration-service/calibration-certificate/purpose-of-a-

Three Reasons Why Calibration is Important

 

 

 

 

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