Scale with Internal Calibration - Do I need to calibrate? How to document this?

N

nikirtehsuxlol

#1
Hi,

I'm trying to write general lab procedures on how to calibrate equipment. Most stuff we calibrate daily and then have an outside source calibrate it yearly.

But there's this one analytical scale that calibrates itself (internal adjustment).

How would you "qualify" this scale for use on a daily basis? Or would you, at all? And how would I document this in my general lab procedures?

I'm pre-thanking you guys. I read this forum and my question seems a bit elementaryyyyyy.
 
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B

badkins1

#2
You don't really mention what this internal scale is associted with (type of equipement) or its length, etc. So I am assuming it is linear with some type of DRO or computer interface. Key factor for anything presumed to be self-calibrating is knowing the original factory accuracy and precision information along with rated repeatability. From there it becomes a matter of running the routine and comparing the run results & repeatablity at certain points along the scale path (Full Scale length with defined segmented points along the scale with the ability of the program to hit each value).

Hope this helps a bit.
 

qusys

Trusted Information Resource
#3
Hi,

I'm trying to write general lab procedures on how to calibrate equipment. Most stuff we calibrate daily and then have an outside source calibrate it yearly.

But there's this one analytical scale that calibrates itself (internal adjustment).

How would you "qualify" this scale for use on a daily basis? Or would you, at all? And how would I document this in my general lab procedures?

I'm pre-thanking you guys. I read this forum and my question seems a bit elementaryyyyyy.
Do you mean that there is an internal software of the scale that allow an automatic calibration?
If so, you can report in your calibration lab procedures this particular kind of calibration , mentioning the affected equipment.

Before the usage of this scale, you can put a "certified" weight on it and check if the read value corresponds ( including the allowed tollerances).
However, check if this scale shall assure valid results based upon your needs and processes. It could be possible to have it only as a reference.
:bigwave:
 
N

nikirtehsuxlol

#4
Do you mean that there is an internal software of the scale that allow an automatic calibration?
If so, you can report in your calibration lab procedures this particular kind of calibration , mentioning the affected equipment.

Before the usage of this scale, you can put a "certified" weight on it and check if the read value corresponds ( including the allowed tollerances).
However, check if this scale shall assure valid results based upon your needs and processes. It could be possible to have it only as a reference.
:bigwave:
It is an analytical weighing scale. Mettler Toledo FACT (Fully Automatic Calibration Technology). From their site: fully automatic, motorized adjustment (calibration) with internal weight.

Do I just write something "This scale uses fully automatic, motorized adjustment ... blah blah technology to calibrate itself. Record weight of 200.000g (w/e it is) calibration weight daily in logbook and check for any decrease/increase in scale weight over time using statistical process control"? Or something similar?
 

qusys

Trusted Information Resource
#5
It is an analytical weighing scale. Mettler Toledo FACT (Fully Automatic Calibration Technology). From their site: fully automatic, motorized adjustment (calibration) with internal weight.

Do I just write something "This scale uses fully automatic, motorized adjustment ... blah blah technology to calibrate itself. Record weight of 200.000g (w/e it is) calibration weight daily in logbook and check for any decrease/increase in scale weight over time using statistical process control"? Or something similar?
Yes, it could be ok.
Is this scale also mantained by vendor or you with a periodical check to assure the good functioning ?
Is there a maintenance program apart for these pieces of equipment ??:bigwave:
 

harry

Super Moderator
#6
It is an analytical weighing scale. Mettler Toledo FACT (Fully Automatic Calibration Technology). From their site: fully automatic, motorized adjustment (calibration) with internal weight. ..............
To me, this is a product feature. Don't you think it needs to be verified to be working/functioning as well as within specified tolerances or ranges? In essence, it is calibration.
 
S

samsung

#7
Hi,

I'm trying to write general lab procedures on how to calibrate equipment. Most stuff we calibrate daily and then have an outside source calibrate it yearly.
Welcome to Elsmar Cove.

Please don't take me wrong but I need to ask a question. What prompts you documenting the calibration procedures for the stuff you calibrate daily?

Probable reasons - customer requirement, errors in measurement attributable to lack of written procedures, high employee turn around or something else?
 

BradM

Staff member
Admin
#8
It is an analytical weighing scale. Mettler Toledo FACT (Fully Automatic Calibration Technology). From their site: fully automatic, motorized adjustment (calibration) with internal weight.

Do I just write something "This scale uses fully automatic, motorized adjustment ... blah blah technology to calibrate itself. Record weight of 200.000g (w/e it is) calibration weight daily in logbook and check for any decrease/increase in scale weight over time using statistical process control"? Or something similar?
I'm not sure what model this balance is, as some of the newer internal calibration processes are quite a bit better than the older ones. However, yes, you can extend the need for external calibrations by using the internal calibration function. Like you mentioned, I would document the drift prior to performing the calibration.

However, I would keep an external calibration activity fairly frequently until you have established consistency. An external calibration is important to verify the accuracy of the internal weights used for the internal calibration, and to verify corner loads. :agree1:
 

BradM

Staff member
Admin
#9
Welcome to Elsmar Cove.

Please don't take me wrong but I need to ask a question. What prompts you documenting the calibration procedures for the stuff you calibrate daily?

Probable reasons - customer requirement, errors in measurement attributable to lack of written procedures, high employee turn around or something else?
Actually a good question. :agree1: Some labs that perform work under guidance of USP 41 (GLP assay measurement stuff) are required to demonstrate appropriate precision and such. Thus, conducting (and then documenting) the daily checks is not unusual. After all, with the FDA, if it is not documented, it did not happen. :D

But after precision and repeatibility is established, many times the frequencies can be extended. To know how far to extend is dependent on the drift error present prior to each daily verification. So that's why it may be good to document things pretty carefully for a while, to lead how far out your interval can go. :)
 
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