Calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler.
"Zeroing" redirects here. For the U.S. government antidumping duties, see Zeroing (trade). For other uses, see Zeroing (disambiguation).
The outcome of the comparison can result in one of the following:
Strictly speaking, the term "calibration" means just the act of comparison and does not include any subsequent adjustment.
The calibration standard is normally traceable to a national or international standard held by a metrology body.
BIPM Definition[edit]
The formal 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."[1]
This definition states that the calibration process is purely a comparison, but introduces the concept of measurement uncertainty in relating the accuracies of the device under test and the standard.
$_$_$DEEZ_NUTS#0__titleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#0__subtitleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#2__titleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#2__descriptionDEEZ_NUTS$_$_$
Calibration may be required for the following reasons:
In general use, calibration is often regarded as including the process of adjusting the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. For example, a thermometer could be calibrated so the error of indication or the correction is determined, and adjusted (e.g. via calibration constants) so that it shows the true temperature in Celsius at specific points on the scale. This is the perception of the instrument's end-user. However, very few instruments can be adjusted to exactly match the standards they are compared to. For the vast majority of calibrations, the calibration process is actually the comparison of an unknown to a known and recording the results.
Basic calibration process[edit]
Purpose and scope[edit]
The calibration process begins with the design of the measuring instrument that needs to be calibrated. The design has to be able to "hold a calibration" through its calibration interval. In other words, the design has to be capable of measurements that are "within engineering tolerance" when used within the stated environmental conditions over some reasonable period of time.[6] Having a design with these characteristics increases the likelihood of the actual measuring instruments performing as expected. Basically, the purpose of calibration is for maintaining the quality of measurement as well as to ensure the proper working of particular instrument.
Frequency[edit]
The exact mechanism for assigning tolerance values varies by country and as per the industry type. The measuring of equipment is manufacturer generally assigns the measurement tolerance, suggests a calibration interval (CI) and specifies the environmental range of use and storage. The using organization generally assigns the actual calibration interval, which is dependent on this specific measuring equipment's likely usage level. The assignment of calibration intervals can be a formal process based on the results of previous calibrations. The standards themselves are not clear on recommended CI values:[7]
$_$_$DEEZ_NUTS#3__titleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#3__subtextDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#4__titleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#4__subtextDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__titleDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__subtextDEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--0DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--1DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--2DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--3DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--4DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--5DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--6DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--7DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--8DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--9DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--10DEEZ_NUTS$_$_$
$_$_$DEEZ_NUTS#1__answer--11DEEZ_NUTS$_$_$