SBS - The best value in QMS software

Recording Weight Values on Calibration Certificates

K

KeithM

#1
Hi,
When calibrating analytical balances in the lab I would like to know if the certified weights need to be entered with the full measurement listed on their certification paperwork or just the stamped value on the weight. For example a class 1 weight of 200g the certificate would add decimal places to show it meets a certain class tolerance. Would it be proper to list it as a 200g weight or a 200.002375 weight. I'm trying to understand why some vendors list their weights using these 2 formats and which one is correct.

My feeling on this is that we do not have the same environment as the test facility so we should just list it as 200g. I've checked Handbook 44 and just can't find it in there.

Along the same lines Gage blocks used for checking Calipers for accuracy I see the same two formats used.

Any help would be appreciated.
Thanks,
Keith
 
Last edited:
Elsmar Forum Sponsor

somashekar

Staff member
Super Moderator
#2
Hi,
When calibrating analytical balances in the lab I would like to know if the certified weights need to be entered with the full measurement listed on their certification paperwork or just the stamped value on the weight. For example a class 1 weight of 200g the certificate would add decimal places to show it meets a certain class tolerance. Would it be proper to list it as a 200g weight or a 200.002375 weight. I'm trying to understand why some vendors list their weights using these 2 formats and which one is correct.

My feeling on this is that we do not have the same environment as the test facility so we should just list it as 200g. I've checked Handbook 44 and just can't find it in there.

Along the same lines Gage blocks used for checking Calipers for accuracy I see the same to formats used.

Any help would be appreciated.
Thanks,
Keith
I am going by logic.
Your class 1 weight would have a traceability to a class 0 and the most correct weight of this is the certificate weight.
The 200 is the typical or nominal weight which is used to call it and is so marked.
So for calibration purpose the standard reference weight is 200.002375g since it has traceability to this weight.
For a weighment purpose it is the marked weight of 200.00 g
Calibration of weights is done in controlled environment and you are required to make the one as specified in the certificate of the class 1 weight. You are talking about 0.01 mg and so need to be sensitive to the required controlled conditions.
Class 1 – Can be used as a reference standard in calibrating other weights and is appropriate for calibrating high precision analytical balances with a readability as low as 0.1 mg to 0.01 mg.
 
D

Daniel Walker - 2011

#3
The advances in electronic weighing technology is making it possible balances to measure masses very accurately. The tolerance of test weights used to calibrate these balances is becoming a significant factor.

With todays micro-balances, the use of ASTM Class 1 weights, or even ASTM Class 0 for that matter, will have their mass errors (correction values) displayed and interpreted as an error of the weighing device. This is the case even if the weights are well within tolerance limits.

If you are testing balances with very small accuracy, repeatability and linearity specs, it is a good idea to evaluate the tolerances of the weights and correction values if they are available. This error is usually not taken into consideration during a balance test but rather included in the uncertainty formula for the test. Plug in the tolerance of the weight(s) and distribute rectangularly to get an uncertainty component that reflects the possible errors of the weights. Sum them together for multiple weights calibrated at the same lab.

If you are using the correction values of the weights and adding the value to the balance dispalay, then that uncertainty component isn't necessary.

It's becoming quite common to fall short of your 4:1 target TUR because of the tolerance (accuracy) of the weights in relation to the ever shrinking balance accuracies. Kind of makes you wonder what the advantage is of even having balances with accuracies so small that they can't even be verified with the highest accuracy mass standards. And good luck getting a primary standards lab to bring out their Class 0 or Class E1 lab standards to test your lab balance. :cool:

Long answer short, if the correction values are significantly effecting your verifications, then i would include the values on the report or add them to your readings. If not, don't worry about it and just list the nominal weight as your test point.
 
D

Daniel Walker - 2011

#4
And.....
if they are significant enough to include, you should also be looking at air buoyancy corrections of the weights and thinking about whether you should use their true mass or conventional mass values.

The difference between the two can get up to the 1-3 mg level at times.
 
K

KeithM

#5
Well the reason I asked is we had a 200g balance calibrated. The weight was listed as 200.0004260 the balance read 199.9997. My supervisor stated that this balance was out of tolerance because 0.00072 was over the stated
+/-.0007 tolerance. I disagreed by stating the 2 should be rounded down to zero and the balance only read 4 places below the gram weighing. When Mettler calibrates our equipment they only list the class and nominal weight value. So I figured there should be a right and wrong here somewhere.
Thanks for the replies so far but I'm looking for a regulation more than an opinion to go by. Then I will let the contractor know whether he needs to change his ways.

:bonk:
 

BradM

Staff member
Admin
#6
Well the reason I asked is we had a 200g balance calibrated. The weight was listed as 200.0004260 the balance read 199.9997. My supervisor stated that this balance was out of tolerance because 0.00072 was over the stated
+/-.0007 tolerance. I disagreed by stating the 2 should be rounded down to zero and the balance only read 4 places below the gram weighing. When Mettler calibrates our equipment they only list the class and nominal weight value. So I figured there should be a right and wrong here somewhere.
Thanks for the replies so far but I'm looking for a regulation more than an opinion to go by. Then I will let the contractor know whether he needs to change his ways.

:bonk:

Wow!! Great responses already by people here.:agree1: I'm a bit confused exactly what you are asking. Is it OK to list the nominal value of a standard? Yes. I can put 200 g weight used, or whatever.

However, (Daniel was getting at this) if listing that value is then going to be used for a calculation/offset of some sort, then the exact value is important.

So, when you ask for a definitive answer, I just want to be clear as to what the question is.:D
 
K

KeithM

#7
Well I guess the real question posed below is was it correct to call this a failure? Keeping in mind that we do not use uncertainties and there is no procedure that tells me to round up or down to begin with. I would think that Mettler would be the method to follow and just list the nominal weight value.


Well the reason I asked is we had a 200g balance calibrated. The weight was listed as 200.0004260 the balance read 199.9997. My supervisor stated that this balance was out of tolerance because 0.00072 was over the stated
+/-.0007 tolerance. I disagreed by stating the 2 should be rounded down to zero and the balance only read 4 places below the gram weighing.
 
Last edited by a moderator:
Z

zamclachia

#8
I don't know your circumstances, however when working with a 4 decimal balance I would set the target value as 200.0004g with an expected range of 200.0011g till 199.9997g. Anything out of this range would require action to determine what the problem is. I assume you are working with 5 decimals. If the limits have been defined as the stated tolerance of the mass piece, then these are the limits that need to be adhered to - no discussion. If the limits are not suitable, look at reassessing them.

I have seen labs that have set tolerance ranges greater that the uncertainty of the mass pieces.
I think what is important is that one has to be pragmatic as to what the requirements / purpose of the measurement are.
 

BradM

Staff member
Admin
#9
Well I guess the real question posed below is was it correct to call this a failure? Keeping in mind that we do not use uncertainties and there is no procedure that tells me to round up or down to begin with. I would think that Mettler would be the method to follow and just list the nominal weight value.
Ahh... understand. First of all, either your tolerance for your balance is set too tight, the class tolerance is not adequate (Daniel's post covered this well), or you simply have moved into the small ratio risk (also covered by Daniel). So if you need that tolerance on your balance and your weights are as good as they get, they you will have to get into assessing uncertainty. Reason being, it's becoming important for you.:agree1:

As far as rounding, given your four place tolerance, five places are significant. So I would state that it is an out of tolerance, and needs to be addressed.

The reason I state that, is I think something needs to change in your process. You really need to clearly identify what your needs are for the balance. If you need four place accuracy, get a six place balance. Also, assure that the weights and processes are optimal.

  • Are you performing internal calibrations?
  • Can the balance autobalance?
  • Are there environmental conditions affecting the balance?
  • Is the interval too long for routine calibration?
  • Can you purchase a few weights and perform in-house verifications?
To me, all of those need to be addressed. So maybe instead of risking having to justify why you did not call it out of tolerance, say it is, and address the process. I would also establish an in-house rule for rounding, where there is no question next time.:D
 
J

jfgunn

#10
Either method is correct. The issue will come down to the reported uncertainties.

If the lab uses the exact value of the weight from the certificate, their uncertainty of the calibration of the balance will be lower because it will not include th tolerance of the weight (instead it will include some estimate of long term stability/drift of that weight).


If the lab uses the nominal vlaue of the weight, their uncertainty of the calibration of the balance will be higher because it will include the tolerance of weight.

Either calibration certificate would likely show that it is possible that the balance failed and possible that it passed.
 
Thread starter Similar threads Forum Replies Date
F Recording Nonconforming Purchased Parts Nonconformance and Corrective Action 5
qualprod Records where apply and stop recording everything? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
R Question on determining defective units - I am not recording fixture to part rejected Statistical Analysis Tools, Techniques and SPC 5
V Recording CMM dimensional results on CFG-1003 APQP and PPAP 3
Marc Informational Apple Tells App Developers To Disclose Or Remove Screen Recording Code World News 0
B Easy Software Needed for Recording Mainly Attribute Data Quality Assurance and Compliance Software Tools and Solutions 2
N Where I can find an Excel sample/template for recording Delivery Time and Cost Excel .xls Spreadsheet Templates and Tools 2
chris1price Error in data recording - Recording measurements in SAP Capability, Accuracy and Stability - Processes, Machines, etc. 2
J Consumer or Medical Grade Tablet to Receive Data from a Recording Module via WIFI IEC 60601 - Medical Electrical Equipment Safety Standards Series 10
R Recording Control Plan Changes Document Control Systems, Procedures, Forms and Templates 3
M SAE AMS 2750E Relocation Hot or Cold Recording Sensor Manufacturing and Related Processes 1
A Recording Data and Data Analysis 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 3
L What is, and the purpose of, ISO STATS recording ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
I Recording of In Process Data to Meet FDA QSR 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1
B Does the recording of wrong entries amount to a nonconformity? Records and Data - Quality, Legal and Other Evidence 7
V Quality Plan (Inspection, Recording and Corrective Actions) Records and Data - Quality, Legal and Other Evidence 2
T Recording of Measured (Variables) Inspection Data vs. Check Boxes Inspection, Prints (Drawings), Testing, Sampling and Related Topics 17
M Recording True Positioning (Geometric Tolerances) on an FAI Report Records and Data - Quality, Legal and Other Evidence 15
C Recording "nature of non-conformities" - Any way out of this?? ISO 13485:2016 - Medical Device Quality Management Systems 7
S Computer Screen Video Capture and Recording Software with Audio After Work and Weekend Discussion Topics 5
K Is Video Recording an Inspection allowed by Auditors? Records and Data - Quality, Legal and Other Evidence 5
K Supplier Performance - Recording Supplier Performance for long term trend reporting ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 8
E Recording Scrap - Problems in the Medical Device Manufacturing Sector ISO 13485:2016 - Medical Device Quality Management Systems 4
F Save Excel file with Date for Recording Weekly Test Samples Records and Data - Quality, Legal and Other Evidence 11
A Validation of an Excel Spreadsheet used for Recording Test Results Qualification and Validation (including 21 CFR Part 11) 14
jkuil Recording of First Piece Inspection to meet 21 CFR 820.80e and ISO 13485 7.5.1.1 Inspection, Prints (Drawings), Testing, Sampling and Related Topics 8
G ISO 14001 - Recording Competence, Training and Awareness in Existing Staff Training - Internal, External, Online and Distance Learning 8
J Simpler Method of Recording In-Process Inspection Data - Machine Shop Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
D Defect Recording Software recommendations Quality Assurance and Compliance Software Tools and Solutions 4
Jen Kirley Have you tried recording vinyl to MP3s and or CDs? Turntable with USB port? After Work and Weekend Discussion Topics 22
P 1st Article Part - Recording All Dimensions vs. Critical Dimensions - AS9100B AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 24
T Recording Inspection Data - Best Practices - What do you folks do? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 16
M Inspection Results - The FDA's interpretation of recording inspection results Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
D Grave 'aide memoire' from a Cockpit Voice Recording (CVR) transcript AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 6
N ISO9001:2000 Documentation/Activities Recording Software ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
N Recording the results of Supplier Evaluation Supplier Quality Assurance and other Supplier Issues 16
G Recording Monitoring and Measuring Readings - Record inspection gages we use? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
M Data Measurement - Where can I purchase a data recording system? Records and Data - Quality, Legal and Other Evidence 2
D Recording training of staff in new/revised procedures Records and Data - Quality, Legal and Other Evidence 7
J Should a Class 1 medical device with an option to measure body weight be considered Class 1m? EU Medical Device Regulations 0
A Is calibration of test weight required General Measurement Device and Calibration Topics 4
S CQI-23 - Molding System Assessment - Control of part weight IATF 16949 - Automotive Quality Systems Standard 5
M Informational FDA discussion paper – Consideration of Benefit-Risk Approaches for Weight-Loss Devices Medical Device and FDA Regulations and Standards News 0
D Measuring fine tubing (< 0.100") "Wall by weight" General Measurement Device and Calibration Topics 11
Q FDA 3500A Reports - Trip and Fall - Weight scale with a fold out platform Other US Medical Device Regulations 1
P Calculating a weight for a machine for the CE label CE Marking (Conformité Européene) / CB Scheme 0
M Informational US FDA final guidance Characterization of Ultrahigh Molecular Weight Polyethylene (UHMWPE) Used in Orthopedic Devices Medical Device and FDA Regulations and Standards News 0
Y How to fix weight tolerance for plastic injection molded part? Does it vary with material groups? Manufacturing and Related Processes 1
M Perform a coating weight test within 3 hours of processing the parts Manufacturing and Related Processes 2
A IMDS - Changing the Locked Weight Value RoHS, REACH, ELV, IMDS and Restricted Substances 1

Similar threads

Top Bottom