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Topic Title: Calibration of Test Instruments
Topic Summary: Are the NICEIC correct?.....
Created On: 16 November 2009 10:56 PM
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 06 December 2009 07:19 PM
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JonSteward

Posts: 675
Joined: 04 December 2007

Thanks for that reply. GN3 calls operating uncertainty 'maximum operating error' (p82).
 06 December 2009 07:38 PM
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intrinsic4225B

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Jon,

Yes - I think GN3 uses the terms basic accuracy and operating accuracy in place of intrinsic uncertainty and operating uncertainty as defined in the BS EN 61557 series of standards.
 11 February 2010 08:23 PM
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busbar

Posts: 181
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The official line from the top men at the NICEIC like Tony Cable is that annual calibratuion is a mandatory requirement, the problem is too many NICEIC inspectors are giving their own interpretation of the rules. This is also a requirement of the HSE as per every other safety critical industry so why do electricians think they are different to everyone else?????

Extract from the operating instructions of the NICEIC checkbox

"This checkbox does not replace the calibration requirements"

This is in writing from NICEIC!! why do contractors believe the spoken rather than the written word??? Answer because alot of them could peel an orange in their pocket, they are too tight to ensure that their tester "complies" with the standard and that they put public safety ahead of their own obsession to skimp on everything.

I use the word comply because many in this post (and many NICEIC inspectors) don't know the difference between accuracy and compliance.

How many of you regurlarly check your tester drives 1mA at 250V/ 0.25M, 500V/0.5M etc on insulation and how many check that it drives 200mA down to short circuit on continuity. Just a couple of the many checks performed during annual certification.

Also every single range needs to be verified to the regulations like all RCD ranges even if you don't use them. If your lights don't work on your car it won't pass the MOT because you say that you only drive in daylight.

On top of all this annual calibration is a requirement from the manufacturers so if you don't do it you lose the balance of your 3 yaer warranty . Simple as
 11 February 2010 08:59 PM
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busbar

Posts: 181
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Exact words direct from NICEIC website

The NICEIC check box provides a quick and simple method of checking the ongoing accuracy of electrical installation test instruments. It does not replace the calibration requirements


Link for reference http://www.niceicdirect.com/ep...op/Products/CB2


All to save less than £1 per week for having a tester verified to the regs professionally.
If I was a contractor I wouldn't just accept verbally what your inspector says, ask him to put it in writing or ask that the NICEIC change waht they put in writing officially in their documentation and on their website as if something ever goes wrong with one of your installations (God Forbid) then you may be facing a very high public liability lawsuit that your insurance might just not cover.
 12 February 2010 01:33 PM
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74jools

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Originally posted by: busbar

Exact words direct from NICEIC website



The NICEIC check box provides a quick and simple method of checking the ongoing accuracy of electrical installation test instruments. It does not replace the calibration requirements






Link for reference ">http://www.niceicdirec.../ep...../CB2





All to save less than £1 per week for having a tester verified to the regs professionally.

If I was a contractor I wouldn't just accept verbally what your inspector says, ask him to put it in writing or ask that the NICEIC change waht they put in writing officially in their documentation and on their website as if something ever goes wrong with one of your installations (God Forbid) then you may be facing a very high public liability lawsuit that your insurance might just not cover.


As I said in my original post in November, I for one will continue having my instruments checked yearly by Fluke, regardless of the comments by the NICEIC assessor.
Its peace of mind as far as i'm concerned.

Julian
 12 February 2010 06:30 PM
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busbar

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Happy to see that you are in that group that use common sense Julian rather than trying to save a few quid without thinking about the reality of the situation.

How can any rational person think that a few resistors or a £100 checkbox can perform all the the functions of a calibrator that costs anywhere between £6000 and £12000 and the people who operate them who like electricians have had to go to college for 2-3 years to gain the qualifications to do it.
It's like me thinking that one of these people who have been on one of these 4 week intensive training courses can replace any of you guys and I even come across electricians moaning about these people and others who have not done the full course and had the relevant experience yet those seem people will spout this bull about checkboxes.

I know electronics and instrumentation and would not attempt to do the job of an electrician so why do lots of electricians think that they can do my job??

As said before your tester can be 100% accurate but still not comply to the regs if it does't meet all of the requirements laid down for test instruments within the standard.
 12 February 2010 08:00 PM
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kj scott

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busbar;
Whilst Tony Cable is a nice fella; he is not the top man of the NICEIC; he is the presenter of their sales and technical presentations. If he has said that calibration is required; then this is at difference to their published guide on instrument accuracy.
The inspectors are correct in their guidance; Where does the HSE state that annual calibration is required for electrical test equipment?
The statement that 'the checkbox can not replace calibration' is simply a covering statement; as of course it would not be suitable for making adjustments to a instrument's range. It is what it says on the lid a checkbox.
 13 February 2010 08:08 AM
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busbar

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Originally posted by: kj scott

busbar;

Whilst Tony Cable is a nice fella; he is not the top man of the NICEIC; he is the presenter of their sales and technical presentations. If he has said that calibration is required; then this is at difference to their published guide on instrument accuracy.

The inspectors are correct in their guidance; Where does the HSE state that annual calibration is required for electrical test equipment?

The statement that 'the checkbox can not replace calibration' is simply a covering statement; as of course it would not be suitable for making adjustments to a instrument's range. It is what it says on the lid a checkbox.


kjscott

Once more yoiu seem to be another one of those talking without really knowing about calibration and interpreting the NICEIC statement to your own advantage. The guidance you are talking about was written by Mark Coles of IET not NICEIC and it was sadly innacurate and is outdated.

Calibration is not about adjustment as you say above, calibration is ensuring that your instrument is within all of the required guidfelines and the full instrument specification, not just at a few random points.

You can compare annual calibration to an annual MOT on a car and adjustment is remedial work like tuning your car if it fails the emmisions test. Please do not confuse the two.

Once more you sayt that the NICEIC inspectors are correct (many of them who inexperienced assessors and are contractors themselves working on behalf of NICEIV), however once more I refer you to the niceic website, their website offers a calibartion service called certificate8 which is recently new and supercedes the paper my Mark Coles , please read the following extracts below and tell me why they should put this in writing on their website and then say that you don't need to have it calibrated. I think some inspectors need to be pointed in the direction of the following as the vast majority give out the correct guidance as below. You as contractors are leaving yourselves wide open if you tke the spoken word over the written.


CERTIFIC8 NICEIC Calibration & Repair Service

Certific8 offers a bespoke, unique and professional Calibration & Repair Service to Contractors registered with the NICEIC and other registration bodies. Enjoy using the service in the knowledge that your Instruments are in good hands from people who really do care and understand what they are doing


What is Calibration and why is it important?
What is Calibration?
Calibration is the process of comparing the accuracy of an Instruments Readings to known Standards whos traceability is maintained by National or International standards.

At Certific8 it also means that your equipment gets cleaned and the case & leads safety checked. You would be amazed at how many Instruments arrive at our laboratory for calibration with taped up test leads, damaged probes and cases with holes in! We aim to keep you equipment inventory in tip top condition by making sure that you get the most from your investment.

Why is it Important?
Within the Contracting Industry, Calibration is important to anyone issuing Test Certificates to clients (Including BS7671 / 17th Edition, Part P and Portable Appliance Testing results.)

Without Calibration you do not have a recognised method of ensuring that the equipment used during these tests is accurate. You may fail installations or appliances that are perfectly fine or more importantly you may issue a pass Certificate on an installation that should have failed and could possibly be dangerous. Put simply, for such a small cost, let's all ensure we do this right.

I have a Checkbox; Can I not just use this and check my own Instruments?
Checkboxes were never intended to replace an annual calibration check. They are intended to be used to confirm on-going accuracy between your annual calibration. Most checkboxes only have a very limited number of values that can be used to check against, compare this to the whole list of readings that you receive from a calibration laboratory who will be checking your equipment on calibrators which costs many thousands of pounds.

By using a lab you can be sure that every range on your equipment is comprehensively checked giving you and your customer peace of mind in the results obtained.

More and more customers are requesting calibration certificates of equipment used on their sites. Showing them a checkbox or a certificate showing half a dozen readings obtained from a checkbox is not really good enough.

The UK's leading test equipment manufacturers including Megger, Fluke & Seaward all recommend annual calibration in a calibration laboratory to ensure ongoing accuracy verification of their equipment.



Reference link http://niceic.org.uk/en/contra...section.asp?SECTION=71
 13 February 2010 09:55 AM
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kj scott

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busbar;
I know the Mark Coles article; but was not referring to it. The guidance I refer to was the NIC EIC guide for contractors; to ensure that they had adequate records of accuracy for their instruments.
So lets discuss calibration; I for many years sent a large quantity of test equipment for regular annual calibration. In that period I received a number of intsruments back which were unfit for service; several intruments were given calibration certificates that were no longer suitable for testing in accordance with IEE recomendations. I then looked at the tracable source used for the insulation continuity test instruments; surprise; a Seward checkbox. Furthermore calibration is carried out at a controllled ambient temperature and humidity; the on site testing is not; so where is the validity of your calibration results when my testing is called into question?
I do not claim to be fully trained a calibration technician; but I am a qualified electrical engineer; and more than experienced enough in testing to recognise if my test equipment is performing correctly.
The calibration service the NICEIC is offering is yet another way of improving their turnover. As has been said in a previous post we do not measure conductor temperature along the whole cable route; we do not even measure ambient temperature when testing.
As regards the field accuracy of live test intruments I have compared various loop testers against each other on a single test point the range of readings 0.8 ohm - 1.23 ohm; it proved a number of things the instuments do vary; and if you carry two sets; high and low ranges if the first test fails; test again with another set. Testing is not the precise art that the intrument calibration fraternity seem to believe it is.
I do not believe that instrument test results alone; would damn or admonish a contractor; as many readings can only be obtained by calculation; not testing.
Calibration has its uses; for example if you find that there is a discrepancy in your test results; or with your checkbox results.
 13 February 2010 11:08 AM
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busbar

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See my replies below


Originally posted by: kj scott

busbar;

I know the Mark Coles article; but was not referring to it. The guidance I refer to was the NIC EIC guide for contractors; to ensure that they had adequate records of accuracy for their instruments.

But that was very much derived from the Mark Coles paper

So lets discuss calibration; I for many years sent a large quantity of test equipment for regular annual calibration. In that period I received a number of intsruments back which were unfit for service; several intruments were given calibration certificates that were no longer suitable for testing in accordance with IEE recomendations. I then looked at the tracable source used for the insulation continuity test instruments; surprise; a Seward checkbox.

Well I would call that lab a bunch of cowboys and you should name and shame them, it is impossible to calibrate using a seaward checkbox . You should have rejected those certificates on receipt and asked for a refund.

Furthermore calibration is carried out at a controllled ambient temperature and humidity; the on site testing is not; so where is the validity of your calibration results when my testing is called into question?

Not always, we carry out calibration in the lab and onsite, these testers have a low temperature coefficient and need to meet the required criterial across the full temperature range so it is irrelevant at what temperature they are calibrated as long as it is noted on the certificate.

I do not claim to be fully trained a calibration technician; but I am a qualified electrical engineer; and more than experienced enough in testing to recognise if my test equipment is performing correctly.

Once more I would dispute this statement, I am a fully trained electronics design engineer not just a calibration technician I could say that I am experienced enough to know if an electrical installation was performing correctly and fit for purpose but

1. I wouldn't be allowed to under the regs
2. I might not pick up something that an experienced electrical engineer like yourself would.

As a example I have come across many testers that have been passed on a checkbox for accuracy yet on a 500V insulation test have only been giving out 35V-100V , accuracy is fine but this does not meet the requirements of the standard and could have resulted in unsafe installations being certified correctly because of this. What would you suggest in this case?? Also I have had many RCD testers that are giving 50% more or double output on the x 1 ranges, so you could be testing a 30mA rcd at 45mA - 60mA without knowing it.
I could go on and on.


The calibration service the NICEIC is offering is yet another way of improving their turnover. As has been said in a previous post we do not measure conductor temperature along the whole cable route; we do not even measure ambient temperature when testing.

I don't disagree and this is the same for every accrediting body, things like ISO9000 , UKAS ISO17025 that we need to have are nothing more than money for old rope but if you need to have them then you need to have them even if you agree or disagree..

As regards the field accuracy of live test intruments I have compared various loop testers against each other on a single test point the range of readings 0.8 ohm - 1.23 ohm; it proved a number of things the instuments do vary; and if you carry two sets; high and low ranges if the first test fails; test again with another set. Testing is not the precise art that the intrument calibration fraternity seem to believe it is.

I never said that it was and that is why I think NICEIC inspectors and some contractors get hung up on accuracy (which is as you say not so critical) rather than compliance with the satndard throughout the ranges.

I do not believe that instrument test results alone; would damn or admonish a contractor; as many readings can only be obtained by calculation; not testing.

Some but not ALL

Calibration has its uses; for example if you find that there is a discrepancy in your test results; or with your checkbox results.


I think the uses go much deeper than this
 13 February 2010 11:34 AM
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John Peckham

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I to have a caried out a comparison test of loop testers at my last years calibration coffee morning.


1 Metrel 61557 0.33 0.5
2 Megger LRCD220 0.35 0.3
3 Megger LRCD220 0.37 0.37
4 Megger 1552 0.38 0.43
5 Megger LTW425 0.391 (0.4)0.39
6 Robin 4120 0.4
7 Megger LTW325 0.4 0.37
8 Megger LCB2500/2 0.41
9 Robin 4120DL 0.41
10 Robin 1620 0.44
11 Robin 4120DL 0.44
12 Metrel Eurotest 0.44 0.4
13 Fluke 1652 0.48
14 Robin 1630 0.54

Mean 0.41 0.39
Median 0.41 0.39
Mode 0.4,0.41,0.44 0.37
Range 0.21 0.2

I have cut and pasted this from an excel sheet but the spacing has gone silly. The 1st figure against each instrument is for the high current range and the second figure is for the low current range.

The Fluke leads were zero'ed out. Only the Robin 1630 failed the calibration test by On Site Calibration services. The test was carried out on my kitchen freezer non RCD socket over a period of about 30 mins.

So what is the Zs then for my kitchen socket?

Out in the field is a very different place to the test bench. If you have high levels of harmonics then you will get fruit machine readings from loop testers more so on the low current ranges.

Bus bar

I am sorry you do not believe me about the eratic readings on the Fluke but they are true. Also I have a dead Megger LCB2000. I had a look inside and found one of the HRC fuses blown which I replaced. It now comes up with the high temprature indicator. It is out of warranty so to expensive to go back to Megger. Is it a bin job or it worth repairing?

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 13 February 2010 11:46 AM
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busbar

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John

It is worth repairing but don't send it back to Megger it will cost you an arm and a leg, if you want details of where to send it to to get a reasonable repair price (probably around £80 including calibration) I will send you some details by PM.
 13 February 2010 06:24 PM
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kj scott

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John;
is your socket somewhere between 0.33 and 0.54 of an ohm?
busbar;
I acknowledge your comments on test results and variances in instruments; but installation test are not that critical; will a 50% increased test current not make the RCD operate quicker? Is an installation with an RCD which has been tested at 45mA instead of 30mA be any less safe?
Incidently Mark Coles article did not precede the NICEIC knowledge; he based it on information gained whilst working for them as an assistant engineer; as the subject was debated at great length during the NICEIC technical conferences; before he left to join the IEE.
Beware also of mistaking an NICEIC Inspecting Engineer for a domestic installer assessor; as they are two completely different species.
The domestic installer assessor is as you correctly state very often a contractor; or a QS of an approved contractor; the Inspecting Engineer is a very experienced engineer; and very knowledgable; also unlikely to comment on any subject that he does not know more than most about. If unsure he will call on the vast resource of his collegues; one of which will know an answer both chapter and verse.
NICEIC; NAPIT; ECA and ELECSA all accept regular comparison of test equipment; in lieu of calibration.
Using your own analogy of the MOT; this does not provethat the vehicle is road worthy for a whole year; it only shows that it meets a range of requirements at that time.
 13 February 2010 08:04 PM
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busbar

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Originally posted by: kj scott

John;

is your socket somewhere between 0.33 and 0.54 of an ohm?

busbar;

I acknowledge your comments on test results and variances in instruments; but installation test are not that critical; will a 50% increased test current not make the RCD operate quicker? Is an installation with an RCD which has been tested at 45mA instead of 30mA be any less safe?

Incidently Mark Coles article did not precede the NICEIC knowledge; he based it on information gained whilst working for them as an assistant engineer; as the subject was debated at great length during the NICEIC technical conferences; before he left to join the IEE.

Beware also of mistaking an NICEIC Inspecting Engineer for a domestic installer assessor; as they are two completely different species.

The domestic installer assessor is as you correctly state very often a contractor; or a QS of an approved contractor; the Inspecting Engineer is a very experienced engineer; and very knowledgable; also unlikely to comment on any subject that he does not know more than most about. If unsure he will call on the vast resource of his collegues; one of which will know an answer both chapter and verse.

NICEIC; NAPIT; ECA and ELECSA all accept regular comparison of test equipment; in lieu of calibration.

Using your own analogy of the MOT; this does not provethat the vehicle is road worthy for a whole year; it only shows that it meets a range of requirements at that time.


Well I'm very sorry but I need to agree to disagree, as I have said before I have a vast experience in all aspects of calibration and requirements of quality systems and have been in the trade since being 18 years old ,so over 30 years, I don't really care what NICEIC inpsectors say as I need to reiterate

1. They are wrong
2. They are putting something different in writing.

Many of you believe what you want to believe.

I am not an expert in electrical testing so tell me why an insulation test is done and why it would not matter if a tester pumped of 50V instead of 500V. I thought it was a safety test to test that there was no potential breakdown between the wires so maybe I misunderstood.

Secondly thercd may trip quicker if it is working correctly but what if it isn't and is tripping at a current much higher than 30mA?

Every contractor I have spoken too who has been told by his assessor that he needn't have his tester calibrated I have left my card and asked him next time he has an assesment to give it to the NICEIC assessor and let him have a discussion about calibration with someone senior within the calibration industry who knows what they are talking about. As of yet I have not had 1 call despite leaving over 50 cards. Enough said.
 13 February 2010 10:21 PM
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RRichard

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Originally posted by: 74jools

Hi all,

Had my annual assessment today, no problems and usual format, but one thing the assessor said has me confused. I have my three Robin Instruments along with my Kewtech check box calibrated annually by Fluke in Norwich, and keep a record of monthly checks on a spreadsheet.

I was told during the assessment that the instruments do not need annual calibration if they check out fine on a continuous monthly check, and more puzzling.......if the check box was purchased from new complete with a calibration cert then unless readings are running out from that expected then the box does not require calibration either.

I will continue to have the check box calibrated annually regardless, but has anyone else been told the above? It doesn't seem quite right to me.



Back to the OP. You are not really having your meters calibrated. You are having them checked to see if they are within the defined tolerances allowed !

I recently asked a well know 'calibrator' how often he has had to make adjustments to any equipment that looked in normal use ( ie not dropped off a scaffold), to which he replied 'never'.

Edited: 13 February 2010 at 10:28 PM by RRichard
 14 February 2010 09:19 AM
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busbar

Posts: 181
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Originally posted by: RRichard

Originally posted by: 74jools



Hi all,



Had my annual assessment today, no problems and usual format, but one thing the assessor said has me confused. I have my three Robin Instruments along with my Kewtech check box calibrated annually by Fluke in Norwich, and keep a record of monthly checks on a spreadsheet.



I was told during the assessment that the instruments do not need annual calibration if they check out fine on a continuous monthly check, and more puzzling.......if the check box was purchased from new complete with a calibration cert then unless readings are running out from that expected then the box does not require calibration either.



I will continue to have the check box calibrated annually regardless, but has anyone else been told the above? It doesn't seem quite right to me.






Back to the OP. You are not really having your meters calibrated. You are having them checked to see if they are within the defined tolerances allowed !



I recently asked a well know 'calibrator' how often he has had to make adjustments to any equipment that looked in normal use ( ie not dropped off a scaffold), to which he replied 'never'.


Do people not read the full thread, the part you have said above

You are not really having your meters calibrated. You are having them checked to see if they are within the defined tolerances allowed !

That is what calibration is m checking the tester on every function and every range to see that it is within specification then certifying it as fit for continued use.

Adjustment is not calibration , that is the biggest misunderstanding that people outside the metrology environment often get confused, as for never having to adjust something well I think he is not a very busy "calibrator" then.

It can vary but Iwould say that 5-10% need some adjustment and another 5% need component chages to allow them to be brought back within limits .

Funny how not many people are commenting on the point one poster made above that insulation tests are not important, and the fact that NICEIC put all of that information in writing on their website.

Do we all still prefer to believe the spoken word? If so that just shows a lack of care and integrity to me, with a disrespect to the people paying you to carry out their testing i.e. the general public
 14 February 2010 09:59 AM
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daveparry1

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That is what calibration is, checking the tester on every function and every range to see that it is within specification
---------------------------------
No, calibration is adjusting to make the instrument accurately display what's being fed into it, checking is to see whether it needs re-calibrating, simple really!
Dave.
 14 February 2010 12:53 PM
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busbar

Posts: 181
Joined: 10 June 2006

Originally posted by: daveparry1

That is what calibration is, checking the tester on every function and every range to see that it is within specification

---------------------------------

No, calibration is adjusting to make the instrument accurately display what's being fed into it, checking is to see whether it needs re-calibrating, simple really!

Dave.


There we go again, someone from a different trade trying to tell me my job of 30 years. It's amazing how people can comment without knowing what they are talking about, you won't find 1 comment from me anywhere on these forums trying to tell any electrician how to do his job simply because they know better than me. However by some posts on here they also seem to know my job better than me too LOL.

Please read the entire threads before commenting

Once more as posted in a post above from NICEIC website

What is Calibration?
Calibration is the process of comparing the accuracy of an Instruments Readings to known Standards whos traceability is maintained by National or International standards.


Definition from UKAS website
Calibration: specific types of measurement performed on measurement standards,material measures and measuring instruments to establish the relationship between the indicated values and known values of a measured quantity. The term
covers calibrations carried out using appropriate reference equipment at any location


Taken from the NPL website where all reputable calibrations are ultimately traceable too
What is the difference between calibration and adjustment? (FAQ - Force)
Calibration is defined as a set of operations that establish, under specified conditions, the relationship between the values of quantities indicated by a measuring instrument or measuring system ... and the corresponding values realised by standards.

Sometimes, however, the word calibration is misused to describe the process of altering the performance of an instrument to ensure that the values it indicates are correct within specified limits (eg adjusting a instrument until its reading agrees with that of another instrument). Strictly this is adjustment - defined as the ... operation of bringing a measuring instrument into a state of performance suitable for its use - and not calibration, although the nature and magnitude of the adjustment is often determined by a pre-adjustment calibration, sometimes known as an as found calibration; such a procedure thus runs:

.first calibration (to determine the approximate magnitude of the adjustment needed)
.adjustment
.second calibration.
Results from the first calibration will also be needed if the device's reproducibility is to be estimated (essentially its change in characteristics over a long time interval).


Reference http://
">
">...ustment-(faq-force)[/B

]http://www.npl.co.uk/reference/faqs/what-is-the-difference-between-calibration-and-adjustment-(faq-force)</[/L]

I take it you agree now
 14 February 2010 01:40 PM
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Jaymack

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I take it there is a poster here who shall be nameless - (Bzzzzar) , with a vested interest in the annual calibration of test instruments, (probably monetary). This is inflationary and certainly not green, transportation has also a risk of the calibration being thrown out, at least I know when there is possible mishandling.

I have 2 sets of test instruments - 1 set is compared with each other and the checkbox, making 3 cross checks and a dedicated RCD for earth trip values. These are ample enough for my needs, accuracies to high values are not required for field work like wot we do.

NAPIT - The Association of Professional Inspectors and Testers concur with my methods at the last assessment; and the NICEIC who don't write the rules!

Regards
 14 February 2010 02:26 PM
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busbar

Posts: 181
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Originally posted by: Jaymack

I take it there is a poster here who shall be nameless - (Bzzzzar) , with a vested interest in the annual calibration of test instruments, (probably monetary). This is inflationary and certainly not green, transportation has also a risk of the calibration being thrown out, at least I know when there is possible mishandling.



I have 2 sets of test instruments - 1 set is compared with each other and the checkbox, making 3 cross checks and a dedicated RCD for earth trip values. These are ample enough for my needs, accuracies to high values are not required for field work like wot we do.



NAPIT - The Association of Professional Inspectors and Testers concur with my methods at the last assessment; and the NICEIC who don't write the rules!



Regards


First of all of course I have a monetary interest, it is my trade, I'm sure that you don't expect me to work for nothing just like I wouldn't expect you to fit an extra socket in my house for nothing, something I would be perfectly capable of doing myself but regulations don't allow me.

You are correct NICEIC don't write the rules they enforce them (or are supposed to) the standard says that your test instruments should be traceable to national standards which in your case they certainly are not . The only way of keeping traceability to national standards is by keeping upto the calibration schedule as reccomended by the manufacturer of your particular tester. Once you go past that it doesn't matter if you do 1000 of your own checks you have lost your traceability and by inference you are breaking the rules of the standard.
Anything goes wrong it will then be you who is prosecuted.

If you think calibration can be thrown out by transportation you are sadly misinformed as these instruments are robust enough to stand that and most now do not have discrete potentiometers that can move they are calibrated by software.

NAPIT are the worst of the lot, they do not know their ***** from their elbow, they were doing calibration roadshows with us 18 months ago (do a search on the net) promoting the importance of getting your tester calibrated every year, they will say what you want to hear in a bid to get you to join them as I have heard first hand.

As for monetary interest I would say that you are one of those minority contractors that I described earlier who could peel an orange in their pocket, irrespective of what is presented to you , you will always believe the thing that you have heard that suits your pocket. You would rather save a couple of quid per week and potentially endanger lives than do what is the correct thing to do. I would never contract someone like you and we are now actively advising the public not to contact an electrician without a valid calibration certificate so if we can't get through to you we will get our message through via the general public and I hope all of those trying to cut corners lose every job they quote for
IET » Wiring and the regulations » Calibration of Test Instruments

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