Measurement Uncertainty and Equipment Accuracy

P

pagnonig

#1
Hi folks,

I'm trying to put together a basic uncertainty calculation method that considers only the most significant contributors.

Now, I'm considering the following three factors:


  • Measurements standard deviation (Type A)

  • Instrument Resolution (Type B)

  • Uncertainty of the reference standard (Type B)

I don't know if (or when) I should add the Equipment Accuracy as declared by the the manufacturer (as Type B) in the calculation.
On the internet I've found contradictory info.

What do you think?

Thank you.
Giuseppe
 
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Mikishots

Trusted Information Resource
#2
Hi folks,

I'm trying to put together a basic uncertainty calculation method that considers only the most significant contributors.

Now, I'm considering the following three factors:


  • Measurements standard deviation (Type A)

  • Instrument Resolution (Type B)

  • Uncertainty of the reference standard (Type B)
I don't know if (or when) I should add the Equipment Accuracy as declared by the the manufacturer (as Type B) in the calculation.
On the internet I've found contradictory info.

What do you think?

Thank you.
Giuseppe
What are the sources of the contradictory info? Are they reputable sources, or just sites with user opinion?
 

dgriffith

Quite Involved in Discussions
#3
Hi folks,

I'm trying to put together a basic uncertainty calculation method that considers only the most significant contributors.

Now, I'm considering the following three factors:


  • Measurements standard deviation (Type A)

  • Instrument Resolution (Type B)

  • Uncertainty of the reference standard (Type B)
I don't know if (or when) I should add the Equipment Accuracy as declared by the manufacturer (as Type B) in the calculation.
On the internet I've found contradictory info.



What do you think?

Thank you.
Giuseppe
Add the reference standard resolution, also, if not already included in the uncertainty provided by the MFR/most recent calibration report.


If it's on the internet it must be true, like what I'm writing now...:D
The UUT/instrument specification is not used when considering the expanded measurement process uncertainty (~k=2). The process, including variation in the readings obtained from the UUT, is what is required to be known, er, estimated...but does not include the UUT tolerance. Otherwise the process uncertainty will usually be larger than the UUT spec!
Equipment accuracy specification would be used for the next budget when the UUT becomes the reference for calibrations down the 'food chain'.

Don
 
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