Specific Requirement for Calibration - ISO 17025 Clause 5.6.2 Interpretations

[midhun926]

I need some clarificaton on ISO:17025 clause 5.6.2.1(specific requirement for calibration)
1. It says " a calibration laboratory estabilishes traceability of its own measurement standards and measurement instruments to the SI systems by means of unbroken chain of calibrations and comparisons linking them to relevent prymary standards of SI units of measurements"

Q1:All the type of calibrations which i perform, is based on respective ISO standards. So what is ment by "establishing traceability of its own measurement standards". my ISO standard will have its own traceability. Why a calibration laboratory has to establish the so called traceability.

Q2:What is meant by"relevant primary standards of SI units of measurements"

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The link to SI unit may be achieved by reference to national measurements standards.The national measurement standards are primary standards, which are primary realisation of SI units, or agreed representation of primary SI units by fundamental physical constants or secondary standards which are standard calibarted by any national metrology institute. When using external calibration services, traceability of measurement shall be assured by calibration services from laboratories who can demonstarte competence, measurement capability and traceability.The calibration certificates issued by these laboratories should contain measurement result, including measurement uncertainty and /or statement of compliance with identified metrological specification.

Q1. What is meant by the terms " primary standards", "primary realisation of SI units","agreed representation of primary SI units by fundamental physical constants, secondary standards and secondary "

 

[BradM]

Maybe this link to SI units will help:

http://physics.nist.gov/cuu/Units/units.html

http://www.nist.gov/ts/wmd/metric/upload/SP1038.pdf

Q1:All the type of calibrations which i perform, is based on respective ISO standards. So what is meant by "establishing traceability of its own measurement standards". my ISO standard will have its own traceability. Why a calibration laboratory has to establish the so called traceability.

Basically whatever instruments/equipment (standards in that sense) that you use, need to be calibrated with an unbroken chain to a national standard. There are equivalent global national standards to N.I.S.T. so your standards you use for calibration should be traceable to those standards.

Q2:What is meant by"relevant primary standards of SI units of measurements"

Refer to the links. Say your using gauge blocks, they should be traceable to the relevant primary standard that has the same unit measure for your standard. You should not have a temperature standard, and have for its traceability a primary standard with an SI unit in Millibars!

Simply put (my opinion) is that you need to be able to demonstrate adequate traceability for the standards that you are using. Hence the reason that 17025 accredited labs are strongly encouraged to use accredited labs to calibrate their standards; to assure adequate traceability (is at least one reason to).

 

[Hershal]

Going a bit further in the standard, Clause 5.6.2.1.1 provides a reflection of the VIM in terms of the requirements.

Typically traceability to SI through National or international standards may be accomplished through a NMI, such as NPL (India). However, the two keys are the unbroken chain of comparisons and the stated uncertainties.

The current edition of VIM phrases it a bit differently, but attaches the same basic steps, and 17025 is based on the earlier version of VIM, so the phrasing is much more clear.

Hope this helps.

 

[George Weiss]

I am a seasoned, maybe over-seasoned calibration lab tech. I work with ISO/IEC-17025:2005
I am not the rocket scientist, and talk more as a friend, so here goes.
Subject:
I need some clarificaton on ISO:17025 clause 5.6.2.1(specific requirement for calibration)
1. It says " a calibration laboratory estabilishes traceability of its own measurement standards and measurement instruments to the SI systems by means of unbroken chain of calibrations and comparisons linking them to relevent prymary standards of SI units of measurements"

Q1:All the type of calibrations which i perform, is based on respective ISO standards. So what is ment by "establishing traceability of its own measurement standards". my ISO standard will have its own traceability. Why a calibration laboratory has to establish the so called traceability.
Answers: I hope this helps…………………….
Q1: Response:
The Calibration lab is expected to show it’s tracability. This is done in several ways.
A flowchart of standards, which links the calibration labs primary, secondary and/or working standards to outside calibration facilities & NIST to establish the tracability.
Examples:
[Nist]-[Cal_lab.primary.std]-[Cal_lab.Secondary.std]-[Working.std]
[Nist]-[Calibration.Vendor]-[Cal_lab.primary.std]-[Cal_lab.Secondary.std]-[Working.std]
The Calibration lab is expected to keep documentation of calibrations of standards, WHICH establishes tracability.
All of your standards will have history files, in a locked cabinet with all calibration records.
It is expected that you know through records that your standards are traceable to NIST directly, indirectly, or to a known and established intrinsic standard.

Q2:What is meant by"relevant primary standards of SI units of measurements"

Q2: Response:
The 17025 standard has to cover a bunch of areas and types of sources and measurements. In short, a calibration lab which has a scope of DCV from 1-1000VDC must have their DCV standard(s) checked. An accredited lab could operate with a Fluke 79 hand held meter as the only calibration standard, to do DCV testing, but most labs have:
DCV 1.00000 , 1.180000 , 10.00000 Primary Reference standards, Fluke 5720A or other calibrators, and HP3458A-002 meters, Divider networks etc.
17025 accreditation and testing expects that if you calibrate a customer’s DUT at 10.00000VDC, then that you have an unbroken NIST link that it was calibrated in DCV, and is expected to be calibrated at 10.00000VDC.
"V" of DCV is the relevant SI

 

[midhun926]

Thank you Hershal.....

 

[midhun926]

thank your valuable information

 

[midhun926]

Thank you for your valuable information

 

[midhun926]

ISO/17025 clause NO:5.6.2.1
In my quality manual.I have included the following


"1.All the equipments/standard used for calibration as well as for subsidiary measurements are calibrated from a reputed calibration laboratory which is accredited by NABL( National Accreditation Board for testing and calibration laboratories (INDIA)).This establishes the traceability of the calibration performed by us, to International System of Units.
2. The calibration certificate of all the above mentioned equipments contains NABL Logo, measurement results along with uncertainty of measurements and the reference to the respective ISO Standard ( just like ISO 9513,which is used for the calibration of extensometer)used for the particular type of calibration."

Question: I believe that the above mentioned points establish the compliance of my laboratory with all the clauses under ISO ISO 17025. clause No;5.6.2.1
*************************************************

Clause No;5.6.2.1.2I
It says"There are are certain calibration that currently cannot be made strictly under SI Units.In these cases, the calibration laboratory should provide confidence measurements by estilishing traceability to appropriate measurement standards such as
1. the use of certified reference material supplied by a competent supplier to give reliable physical or chemical characterisation of the a material)
2 the use of specified methods and /or consensus standard that are clearly described and agreed by all parties concerned."

Question : I am planning to do calibration for
1.Universal Testing machine (Force measurement using Force proving Ring)
2.Extensometer (which measures elongation)
3.Impact testing machines
4. hardness testing machines

I believe that the above mentioned clause is applicable my calibartion , because, in case of calibration of hardness testing machines, i use Hardness Test Blocks of having specified Hardness . the results of hardness calibration is mentioned as HRA,HRB( If the Equipment Under Calibration is is Rockwell Hardness tester) which are SI Unit.I dont think there is an SI unit for Hardness.But the test blocks that I am using are Calibrated from an NABL Accredited Lab ( like i said, it contains NABL Logo and other details). Is it enough to satisfy the the requirement of the above mentioned clause

 

[midhun926]

i have a question.what is meant by reference standard and reference material?
I am using Hardness Test Blocks ( having different Hardness value) for the calibration of hardness testing machines( vickers, rockwell, brinnel etc). Are these test blocks coming under reference standards or reference materilal ?

ISO 17025 Clause No:5.6.3.3 says that "checks needed to maintain the confidence in calibration of primary, reference,transfer or working standard shall be carried out definite procedures and schedule."

1. What is mean by the terms which are marked red?
2. If i have Hardness test block ( i guess test block is an example for reference standards) used for calibration of Hardness Testing machines, it is conspicuous that it is a calibrated one and the validity of that calibration is one year.Since the laboratory have policies and procedures for internal I feel that the internal checking for this will come under clause No:5.5.1.0

 

[George Weiss]

I qualify by saying, "I believe, and in my version of people speak".

Accredited testing is tracable to standard. NIST is the USA source of these acceptable standards, and NIST only indirectly accredits facilities in areas that NIST has scope, and the facilities have these qualified standards in use for their scope of accreditation. 1) the SI units standards, (volt for example), 2)SRM, (standard reference materials), 3) established intrinsic standards. The materials used for testing the Rockwell hardness tester would fall into #2, the SRMs. Like other standards, these items have their condition/status calibrated, and tracked like other calibrated standards. Your metal reference plates come from an accredited source. GREAT!
A point worth mentioning, in response to item #2, which is:
2 the use of specified methods and /or consensus standard that are clearly described and agreed by all parties concerned."
This is a phrase, which covers the method and extent of calibration. This phase allows that:
Any number of tests is OK as long as the calibration facility and customer agree to it’s being acceptable. In the case of the Rockwell tester, several metal hardness standards are used. It can be acceptable to use: 1,2,3,or 10 metal plates, and test each 1 or 3 or 10 times, as long as the parties agree to the method(s). Accredited calibration process agreement might come in the form of a contractual calibration policy for single instruments, or groups/types of instruments. The accredited calibration report, which includes, the tests performed, the results, the test limits, and uncertainties, can become the established means of reporting the method. In effect, all tests are reported, and these are the agreed upon tests. Having the testing agreed upon in writing is a prudent action. Sometimes less testing is a more cost-effective calibration, and allows a competitive advantage. It is safe to calibrate an item as listed in a manufacturer’s manual, but other methods and extent of calibration are also acceptable, if agreed to.
Hope this helps…..