Accuracy of test instrument

[lofty84]

state three methods for checking the accuracy of test equiptment.

calibration
check box
check against someone elses meter

can you think of anymore ?

If an instrument is found to be inacurate after tests have been completed list three ations which should be taken

what would be your standard procedure for this ?

 

[Golden_Boy]

I just use a collection of resistors why pay £'s for a fancy box when pennies will buy you a handful of resistors that will do the same job

My sentiments exactly........

 

[Martin Bradley]

It cost me a total of £5 cheap as chips. And the resisters wont get lost. or damaged, so what is the diff between, having and inclosure and not,
Better than sitting down doing nowt.
And im glad my home made box looks fancy, as it impressed the NICEIC.

 

[Golden_Boy]

I'm still waiting for an explanation of " calibration" ????
If I dont get a reply I will assume its one great big CON.

 

[UNG]

I'm still waiting for an explanation of " calibration" ????
If I dont get a reply I will assume its one great big CON.

How have you got this far without understanding calibration and the need for it. Every time you null (zero) your meter for an r1 r2 test you are carrying out a form of calibration. It may help you understand calibration if you read this

Calibration - Wikipedia, the free encyclopedia

In a nutshell your meter is compared with a known standard source when your meter is checked (calibrated) against this you should receive a list detailing it's readings / accuracy on all it's ranges and functions

If it is a great big con then there are a lot of gullible people out there who have been ripped of for many years, I don't think it could have gone on for this long if it was or are you blowing the lid on it

 

[Golden_Boy]

Quoting from that document
"
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. 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."

I always understood Calibration to require some sort of adjustment but not in this case, only a report stating the accuracy is needed? So in my understanding of the english language its not "calibration" at all, Merly the production of a report telling the owner how good ( or indeed BAD ) the kit is!

 

[UNG]

I always understood Calibration to require some sort of adjustment but not in this case, only a report stating the accuracy is needed? So in my understanding of the english language its not "calibration" at all, Merly the production of a report telling the owner how good ( or indeed BAD ) the kit is!

Unfortunately that is the price of progress as we move away from moving coil meters to electronic meters then adjustment becomes difficult to impossible to do and all we can hope for is a report detailing the accuracy and whether it falls within useable limits

 

[tom-the-sparky]

Hi Martin Bradley

Oh man i am impressed with your box!! I've got my niceic assesment next week and im trying to set up my own check box but dont know where to start, can you help?

Thanks very much

 

[Knobhead]

Now can anyone explain what the hell this means?

UNCERTAINTIES

The reported expanded uncertainties are based on a standard uncertainty multiplied by a coverage factor k=2, providing a level of confidence of approximately 95%.


CERTIFICATE OF CALIBRATION
DOWDING & MILLS Ltd.
CALIBRATION CERTIFICATE NUMBER 22425/02/010
As Received Calibration Results
22425/02/010

Fluke 77 Series Ill Digital Multimeter
79450647

29 Mar 2006
Joe McCracken


TRACEABILI1Y INFORMATION:

INVENTORY NUM BER INSTRUMENT DESCRIPTION:
IS 1581 WAVETEK 9105 CALIBRATION SYSTEM

PROCEDURE

The instrument was allowed to acclimatize in the laboratory for a period in excess of two hours. The calibration was carried out by connecting the instrument to calibrated sources, which were also measured as necessary. The AC waveform was substantially sinusoidal.

UNCERTAINTIES

The reported expanded uncertainties are based on a standard uncertainty multiplied by a coverage factor k=2, providing a level of confidence of approximately 95%.