Interval for Self-Calibrating Measurement Device?

Crusader

Trusted Information Resource
#1
We have a gauge that self-calibrates - it even says so in the user manual! The gauge is set for annual calibrations by the manufacturer. It has expired now. The company has decided to not send out for calibration since this thing can self-calibrate. I'm in a pickle. I guess I can extend the calibration to next year based on past results (previous years of external calibrations).

What do you think? :confused: My 3 year recert is next year. I'm nervous that we'll get hit with a finding. I warned the company but I lost the battle.
 
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Michael_M

Trusted Information Resource
#2
Do you have a method of 'verification'? For example, we have an optical micrometer that does not require 'calibration', however, we have some XX gage pins (that are calibrated) which we use to verify the device is still measuring correctly.

Can you do something like this?
 

Crusader

Trusted Information Resource
#3
Do you have a method of 'verification'? For example, we have an optical micrometer that does not require 'calibration', however, we have some XX gage pins (that are calibrated) which we use to verify the device is still measuring correctly.

Can you do something like this?
It is self-calibrating, and I do not have a second gauge to check the piece that is used in the self-calibration. There really is no verification.
 
J

JoShmo

#4
It is self-calibrating, and I do not have a second gauge to check the piece that is used in the self-calibration. There really is no verification.
There is no such thing as "self calibration" and - I've encountered this before - the manufacturer doesn't understand "calibration" per the VIM. The best it is is a self verification. What are the units it's measuring?
 

Crusader

Trusted Information Resource
#6
Are you able to tell us exactly what it is? Might help us trouble shoot for you.
It is a gloss meter - I attached a similar model owner manual. But the owner manual does state it is self-calibrating. I want to do the right thing and keep my employer happy and meet the ISO standard at the same time. And Thanks for replying!
 

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Ron Rompen

Trusted Information Resource
#7
A gloss meter 'self calibrates' by measuring the reflection from a known standard. The problem with this is the known standard becomes dull and less glossy over time and with use.
You can purchase a new 'standard' and use it as the annual comparison/verification one, and continue to use the original one for daily self-calibration (at least until it fails to match up with the 'new' standard).
I ran into exactly the same thing a few years ago, and this is how I dealt with it, and this is what my customer (and my auditor) approved.
 
B

BoardGuy

#9
It is self-calibrating, and I do not have a second gauge to check the piece that is used in the self-calibration. There really is no verification.
Just because a piece of equipment says it “self-calibrates” does not mean that this method assures that it is measuring correctly. ISO 9001, AS9100, and ISO 13485 clearly states that where necessary to ensure valid results, measuring equipment shall be calibrated or verified or both at specified intervals, or prior to use, against measurement standards… (7.6)

Your problem is how you verified that the measurement results from this piece of “self-calibrating” equipment are valid and what records you will retain showing you verified this equipment. Since you do not state what the equipment is its little hard to advice you on a method that could be use to verify the equipment but there is always a way.
 

BradM

Staff member
Admin
#10
Newer equipment/instrumentation have features/functions that allow for internal adjustment/alignment of the measurement capability. For example, newer analytical balances have internal standard weights that can be used to verify the balance is weighing correctly. However, there are many factors that can affect the accuracy/repeatability of a balance. Too, the internal weights on the balance need to be verified routinely.

Depending on how robust/ accuracy the "self-calibration" routine is on a piece of equipment can extend the calibration frequency/interval. However, for a true calibration of measurement equipment/instrumentation, a known standard with NIST (or equivalent) traceability is needed; and an assessment of uncertainty (or accuracy) ratio.

So if you don't want to pay an outside vendor to perform the verification, you should consider acquiring the standard yourself and determining what interval that standard should be re-verified. Also, you should have a procedure/work instruction written to address the needs.
 
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