Considering addition of mass calibration to ISO17025 scope

Q

QMTguy

Registered
I work for a company that is already ISO17025:2017 accredited for calibration of scales/balances. They want to consider expanding their scope to include the calibration of weights that would be used in a laboratory setting. We already have our own analytical balance (capable of 0.01mg for up to 41g, 0.1mg for up to 210g) and a 22 piece analytical weight set (Class 1 - 200g-1mg). I was thinking we could use those and follow Annex C of OIML R 111-1 to offer mass calibration services.

I am curious if anyone can share their experiences and/or insight having to add mass calibration to their scope?

Do any of you provide a similar service?

Any resources to help identify which ASTM class we should target or identify as being able to calibrate to?

Any additional insight or feedback would be much appreciated.

Thank you.
 
D

dwperron

Trusted Information Resource
QMTguy said:
I work for a company that is already ISO17025:2017 accredited for calibration of scales/balances. They want to consider expanding their scope to include the calibration of weights that would be used in a laboratory setting. We already have our own analytical balance (capable of 0.01mg for up to 41g, 0.1mg for up to 210g) and a 22 piece analytical weight set (Class 1 - 200g-1mg). I was thinking we could use those and follow Annex C of OIML R 111-1 to offer mass calibration services.

I am curious if anyone can share their experiences and/or insight having to add mass calibration to their scope?

Do any of you provide a similar service?

Any resources to help identify which ASTM class we should target or identify as being able to calibrate to?

Any additional insight or feedback would be much appreciated.

Thank you.
Click to expand...


First thing we need to know is what your measurement uncertainties will be. You really can't do anything without those numbers.
 
Q

QMTguy

Registered
Would uncertainties for the items listed below be enough?
- Repeatability of the balance
- Resolution of the balance
- Linearity of the balance
- Uncertainty from balances calibration

I've tried researching this topic and have come across multiple examples using different factors for their budgets and it isn't clear to me which I should or shouldn't use.
 
Q

QMTguy

Registered
After some additional research I believe NIST SOP 8 may be a better suited calibration procedure to consider. Using our Class 1 weights, analytical scale, and modified substitution would it be reasonable to propose we calibrate to NIST Class F and ASTM E617 Classes 6, 7 weights/masses? Our uncertainty budget would expand to include the weight being compared for each mass.

Does that sound right?
 
D

dwperron

Trusted Information Resource
QMTguy said:
Can @dwperron or anyone else offer any additional feedback? Thanks and have a great weekend.
Click to expand...


The folks at NIST not only gave us SOP 8, they also gave us examples of uncertainty budgets.
Page 3 of this document is the example for SOP 8.
Where you are talking Class F / 6 / 7 weights then some of the terms will not be "significant", and you can drop them.
On the other hand, I have faced auditors who demanded that I use those terms saying "How do you know they are insignificant if you don't apply them?"

https://www.nist.gov/system/files/documents/2017/04/28/uncertainty-budget-tables.pdf
 
You must log in or register to reply here.
Top Bottom