Accuracy of test instruments for NIC

[electrospark]

Hello all,

I'm in the process of becoming NIC registered and just waiting for my assessment date now.
One thing I need to get in place is an accuracy record of test instruments. In my current job we use a transmille every month to monitor the test kits but I don't really want to fork out for one at this early stage. Is there other ways I can do it, ie a dedicated circuit I can test?
Also my tester is 18 months old and hardly used as I also have a company tester. Will I need to have this calibrated for my assessment?

How does everyone else do theirs?

Thanks

 

[EFLImpudence]

You will need a calibration certificate from a recognised source for each instrument to start.

After that you may continue to verify that it is still accurate using a check box or reliable equipment or accessories.
I.e. same circuit, resistors, RCD etc.

 

[ban-all-sheds]

Also my tester is 18 months old and hardly used as I also have a company tester. Will I need to have this calibrated for my assessment?

Can you get yours calibrated through the company?

 

[ban-all-sheds]

Re check box, you can buy or make.

You need a selection of low-value resistors to check your [JW2 STOP] continuity tester [/JW2 STOP].

A selection of high-values to check the IR tester.

A socket with a switchable 1Ω resistor in the E connection to check your loop tester. Or a designated circuit at home if you're sure it never varies.

Optionally, an RCD.

Fresh from calibration you log what you get from your box, and then repeat at suitable intervals. The idea is that the readings should not change. If they do it's recalibration time, although NICEIC may insist on annual calibration anyway.

 

[JohnW2]

You need a selection of low-value resistors to check your [JW2 STOP] continuity tester [/JW2 STOP].

Kind Regards, John

 

[flameport]

How does everyone else do theirs?

Annual calibration certificate, which is all that ELECSA want to see.
Monthly/weekly checks and using test boxes etc. not required or even mentioned.

 

[EFLImpudence]

I was meaning that if you do regular checks after initial calibration, proving the instrument is still accurate, you may skip calibration for two or three years.

 

[JohnW2]

I was meaning that if you do regular checks after initial calibration, proving the instrument is still accurate, you may skip calibration for two or three years.

Do the scheme providers (or, at least, some of them) not want to see annual calibration certificates?

Kind Regards, John

 

[Taylortwocities]

NAPIT want to see a calibration cert to start with and is then happy to see (recorded) monthly checks done on a checkbox.

Electrospark - ask around in your local electrical distributors. They often have calibration days and its usually cheaper - and more convenient - than sending your kit off for checking.

 

[JohnW2]

NAPIT want to see a calibration cert to start with and is then happy to see (recorded) monthly checks done on a checkbox.

Indefinitely - or do they want to see a new calibration cert after some period of time?

Kind Regards, John

 

[EFLImpudence]

I was told by Elecsa that calibration may be acceptable every three years but never got that far.

Logically, if the meter is still reading accurately, there is no reason to require calibration - but logic probably doesn't come into it.

 

[JohnW2]

I was told by Elecsa that calibration may be acceptable every three years but never got that far. ... Logically, if the meter is still reading accurately, there is no reason to require calibration - but logic probably doesn't come into it.

Is not one of the issues perhaps the fact that there knowledge that "the meter is still reading accurately" is reliant on them trusting what you have told them, whereas 'calibration' is, at least theoretically, undertaken by an independent company.

Is not another issue that, unless one has access to a very fancy (aka expensive) 'check box' or whatever, one will only get limited or indirect evidence of accuracy in relation to loop impedance measurements and RCD tests?

Kind Regards, John

 

[electrospark]

Thanks for all the replies. I think I will just have It calibrated for assessment any how and then buy a check box. I found one for £35 which is a fraction of the price of a transmille.

http://www.tester.co.uk/calibration-checkbox?gclid=CNKxibKB88YCFa3MtAod_iwOww

Take a look, what do you think?

 

[JohnW2]

Thanks for all the replies. I think I will just have It calibrated for assessment any how and then buy a check box. I found one for £35 which is a fraction of the price of a transmille. ... http://www.tester.co.uk/calibration-checkbox?gclid=CNKxibKB88YCFa3MtAod_iwOww ... Take a look, what do you think?

It appears to just be a box containing 9 resistors (at the cost of many hundreds of resistors ), which would be fine for checking the low resistance ("continuity") and IR functions of your kit. However, although they say "With direct access to a socket, this calibration checkbox can also be used to test RCD and earth loop impedance.", I'm not sure what they have in mind.

In terms of loop impedance, AFAICS, the only thing one could do would be to insert small resistances (from the box) in series with the fault loop path and see if the loop impedance indicated by you meter increased by the same amount - but that's not quite a full test of the functionality.

As for RCD testing, I really can't imagine what they can be thinking of. Even in terms of just creating an L-E fault current to cause an RCD trip, there aren't any appropriate resistors there - 10Ω would result in a fault current of 23A (which would blow up the resistor unless there is a fuse!), and the next one up (0.5MΩ) would result in a fault current of only 0.46mA, neither of which is of the slightest use - so I don't see how it could be used to check measurements of RCD trip threshold, let alone trip times.

Kind Regards, John

 

[Taylortwocities]

You can buy the bits at Maplin for less than a tenner, and you'll have fun with a soldering iron while you are at it!
My NAPIT guy was happy to see proof that I was checking the relative consistency of the tester on a regular basis. Can't comment on other scams though.