Calibration

CALIBRATION
CALIBRATION
CALIBRATION
CALIBRATION
Procedures,
Procedures,
Standard
Standard
And
And
Methodologies
Methodologies

Introduction
• In this section, the procedures and
methodologies to carry out a
calibration will be discussed. In
addition, the approach to calculate
errors in a calibration will be shown.

Objective Of Calibration
• The prime objective of calibration is
to ensure that measurements taken
are accurate at all times taking into
consideration wear and tear,
degradation and abuse. It is with this
in mind that we need to adopt and
appropriate methodology to do a
proper calibration.

cope of Calibration
In developing a calibration program, the following
should be taken into consideration !

Involve all testers or those who use measuring and
test e"uipment

Calibration must be conducted on all e"uipment used
to verify product compliance.

#ngineering measuring e"uipment must all be
calibrated.

$ierarchy of tandards
• The hierarchy of standards used in a calibration is shown as
follows !

 %rimary or &ational standards are the ultimate reference standards for determining a
measurement. 's an e(ample, a standard measurement of a meter is set by a steel rod of
this length which is the primary standard. 'll other standards used to conduct a
calibration must be checked with reference to this standard from the working to the
reference standard


%rimary
tandard
)eference tandard
*orking tandards
+easuring , Test #"uipment

tandard 'de"uacy
• *orking standard used to calibrate internal measuring
e"uipment must be traceable to either a &ational or %rimary
tandard. In addition, their accuracy must be 4 to 10
times more accurate compared to the e"uipment to be
calibrated. -or instance, portable water analy.er such as p$
meter, &T/ meter with the standard measurement scale,
can be calibrated internally by using the standard solution
that provided.
• Occasionally, an e"uipment may be state of the art and
hence, there is no reference standard available. In this
case, this e"uipment can be calibrated with another
e"uipment of the same type, make and model.

Traceability of Calibration
• In a country, a calibration must be traceable to a &ational
tandard held by a national body 0eg. I)I+ or other
government agencies of +alaysia1. If this national standard
is not available. The calibration must be traceable to
another country. Traceability of a calibration is important
as an incorrect reference standard used will not ensure that
the e"uipment calibrated has the re"uired accuracy.
• 's most companies send out their e"uipment for calibration,
mandatory that they check the capability of the calibration
agent. Those that are certified to the IO 2333 4uide 56
will be able to provide an appropriate traceability. -or
others, you will need to check the reference standards used
and their respective traceability.

-actors to Consider in a Calibration
• Calibration #nvironment
• Interval of Calibration
• 'ccuracy of tandard +aster
• Out of Tolerance #"uipment
• ubcontractor Controls
• /ncertainty of +easurement
• $andling the torage
• Identification and tatus of Calibration
• Training
• 7ocumentation and )ecords

Calibration #nvironment
#nvironment conditions which could affect a calibration are as follows. This will largely
dependent on the sensitivity of an e"uipment to the various conditions. Consult the
e"uipment manufacturer to determine the appropriate environmental conditions
re"uired to do a calibration.
• Temperature
• $umidity
• 8ibration
• 7ust
• &oise
• 9ight
• 'ir +ovement
• +agnetic -ield
ome e(amples where controlling certain environment factors is critical for the
different types of measurement are as follows !


Chemical 'nalyses : p$ value and &T/ are critical

Interval of Calibration
•
Interval between one calibration to another is an important aspect to ensure the
continuing accuracy of an e"uipment. This must be established for all measuring and
test e"uipment, each may be set at different intervals dependent on the degree of
usage and other factors such as!

; tability
; -re"uency of /se
; 'ccuracy
; %urpose of /se
•
If you are unsure which is the best interval to choose, always follow the e"uipment
manufacturer<s recommendations. This interval should be reviewed from time and as a
rule of thumb, it should be adjusted based on the calibration history. -or e(ample, if
an e"uipment is calibrated on a si( monthly basis and it is found to be out of
calibration fre"uently, then the calibration interval should be changed either 5 or =
monthly.

C'9I>)'TIO& I&T#)8'9
• *hat actions and the calibration interval on the e"uipment would you recommend to
the user for the following !

?. 'n instrument is found to have failed 5 times in the last 5 calibrations
performed at @ monthly intervals.
5. ' newly purchased p$ onAline analy.er which will be used in production daily.
Calibration interval recommended by manufacturer is = monthly.
=. ' +agnetic -low +eter used to measure the flow of water with
specification of 3.6 to ? B accuracy.
'ccuracy of +agnetic -low +eter is 3.6 to ?B with Calibration interval of
yearly using the -low +eter 8erificator.

'CC/)'CC O- )#-#)#&C# T'&7')7
• 's discussed in the previous section, the
reference standard used to do a calibration must
be at least D to ?3 times more accurate than the
e"uipment. In general, a 26B confidence level is
preferred and this gives a E 5 sigma (standard
deviation) or D sigma capability in a measurement.

O/T O- TO9#)#&C# #F/I%+#&T
• *hen an e"uipment is found to be out of tolerance or not having the re"uired
accuracy, certain steps must be taken. 'ctions to be taken include decisions on
whether the e"uipment can be used or not and what needs to be done on the affected
products as follows !
; )eview all measurements prior to and after adjustment is made to the
affected e"uipment.
; 7ecide on whether the e"uipment can be used or has to be thrown away
or used for lesser accuracy measurements.
; )eview previous batches of products 0 ? week or more1 where
measurements have been taken using this out of tolerance e"uipment
prior to and after an adjustment has been made to correct the out of
calibration situation. 7ecide whether they meet specification or not.
; If the e"uipment can be used but needs correction to their readings, then the
compensation or offset factors must be stated on the e"uipment.


ubcontractor Controls
• In choosing an appropriate subcontractor to perform your
calibration, it is critical that an accredited calibrating lab
or agent is used 0those certified to IO 2333 4uide 561.
'sk for a copy of their certification before selecting them.
Cou will also need to ensure that the reference standards
used by the calibrating lab or agent is traceable to national
standard. The calibration method used should also be
checked to ensure they used an appropriate or recogni.ed
procedure. >oth of these re"uirement can be verified on
their Certificate of Calibration, which is issued to you upon
completion of a calibration for each set of e"uipment.

/ncertainty Of +easurement
The uncertainty of measurement of a calibration needs to be
calculated to determine all the possible sources of errors. It is
given by the formula !
/ncertainty of +easurement G E t 0from a tudents tAtable1 ( s
0standard deviation of variation1.
As a rule of thumb, the uncertainty of measurement must not exceed
30% of the tolerance of a measurement. If it does, it’s mean that the
equipment is not suitable for use as its required accuracy is not
sufficient. A measurement taken using this equipment ill gi!e a false
or inaccurate !alue.

$andling and torage
• The proper handling and storage of measuring e"uipment and their
reference standards are an essential part of establishing an
effective Calibration %rogram. ome of the guidelines to follow are
as follows!

$andling : ensure the e"uipment is appropriately handled during use, storage and
transportation.

%roper torage : ensure e"uipment is stored in their respective casing or special
storage container under appropriate environmental conditions as re"uired.

%roper %acking for Transportation : ensure the e"uipment is appropriately packed to
protected them from movement and damage during transportation 0eg. /se Hbubble
bagsI or impact absorbent materials1.

Check that the calibration status is valid before issuing an e"uipment for use
0especially newly purchased e"uipment1.

#nsure that the e"uipment is appropriately sealed with a tamperAproof sticker or
marking, etc to prevent unauthori.ed adjustment or repair.

Identification and tatus of Calibration
• /pon completion of a calibration, each e"uipment
must be appropriately labeled to indicate their
status. 7epending on the si.e of the e"uipment, it
may not be possible to attach a calibration label
on all instruments. -or an e"uipment such as
thermometer it may not be practical to stick such
a label. Therefore, other means such as color
coding can be used instead of a label to indicate
their calibration status. 'lternatively, the label
may be attached to the casing or container.

#(ample of the various labels or identifications which can be used are as
follows!
• %assed Calibration
• Tamper %roof 9abel
These labels are used to prevent tampering on the e"uipment after it is calibrated.
'n e(ample is as follows !

I"#$ "A%&$
'($ ")&$
VOID
*alibration +eal
If 'roken
PBA

• H7O &OT /#I 9abel
This label is used to indicate that a specific e"uipment cannot be used either
because it is damaged or needs repair or malfunctioned or its calibration is out
of tolerance.


• H&o Calibration )e"uiredI 9abel
This label is used to indicate those e"uipment which do not re"uire any
calibration. These are mainly those used for rough measurement and for which
accuracy is not important. ome e(amples are process instrumentation such as
chlorine analy.ers and ultrasonic level sensor, etc.
DO NOT USE
PBA
%erbadanan >ekalan 'ir
%ulau %inang dn. >hd.
CALIBRATION NOT
REQUIRED
%erbadanan >ekalan 'ir
%ulau %inang dn. >hd. PBA

Training
• %ersonnel appointed to perform calibration must
be appropriately trained together with proper
education and e(perience. They must understand
the characteristic and features of an e"uipment,
and its usage 0ie. )e"uired accuracy, stability,
sensitivity, etc1. -urthermore, the personnel must
know the calibration procedures and
methodologies including the calculation of
uncertainty of measurement and sources of
errors. 8arious training courses are now available
and those responsible for performing calibration
must attend these courses.

7ocumentation and )ecords
• 'ppropriate documentation and records must be maintained as
part of a calibration program. #ssential ones are as follows !
a1 Master List of Equipment
' master list of e"uipment shall be maintained to indicate all the measuring e"uipment used in a
company. It should state as a minimum, the following details !


#"uipment Identification 0I71

9ocation

)e"uired 'ccuracy

+easurement )ange

Calibration Interval

Calibration 9abJ'gent 0internal or e(ternal1

7ate Calibrated

7ate due for &e(t Calibration

%ass J -ail Calibration

b1 Calibration Plan

-or each type of e"uipment, a calibration plan shall be developed. This plan shall
outline all the steps to conduct a calibration including !

)eference standards to be used K

)ecording methodologies K

#nvironmental conditions for calibration K

Calculations K

'pproach to handle an out of tolerance situation.
The plan should also outline the recalling system to ensure each piece of e"uipment is
calibrated either on or before their due date. ' reminder system or calibration
schedule is necessary.
c1 Training Reords

Training records shall be maintained for all personnel authori.ed to perform
calibration.

d1 !ut of Calibration "otie and Reords

&otices advising the relevant department and personnel of an e"uipment found to be
out of calibration and the corresponding actions 0s1 taken shall be maintained.

e1 Manufaturers# $andboo%s

+anufacturers< handbooks or reference manuals used as part of calibration shall also
be controlled and kept by the department responsible for calibration.


f1 Calibration Certifiate

Calibration certificate provide by an e(ternal calibrating organi.ation must be kept
as proof of calibration and are to be maintained as part of the calibration records.
Internal calibration certificate also re"uired to be kept at the respective cost
centre.

g1 Reords of &sage
)ecords of usage are to show the persons who have used the e"uipment and to
indicate the degree of usage and what measurements were taken.
h1 Measurement Equipment $istor' Reord
' history record should be maintained for each piece of e"uipment. It should contain
the following details !

make, model and type or brand

date of purchase

department using this e"uipment and its location use

date of first calibration

adjustment made during calibration 0if any1

repair , service details

action taken on out of tolerance situation 0if any1

date of disposal 0when it is unusable1.

T(an% 'ou
%repared >y!
Mohd Suhaimi Shariff