SBS - The Best Value in QMS software

Uncertainty budgets and meeting 4:1 TUR for digital calipers and micrometer

#1
Hello,

I am working on coming up with uncertainty budgets for the calibration of a 6 inch digital caliper with a resolution of 0.0005 inches and a 1 inch digital micrometer with a resolution of .000005.

The goal in the end is to have our calibrations comply with ANSI/NCSL Z540-3 when it states "the test uncertainty ratio shall be equal or greater than 4:1"

So far, I have the following factors in my uncertainty budget, with values for measuring a 1 inch gage block at 72 degrees Fahrenheit.

- Uncertainty due to resolution: 238 μin for caliper, 23.8 μin for micrometer
- Uncertainty from the gage blocks used in calibration: 16 μin for both
- Uncertainty due to thermal expansion and contraction: 14.6 μin for both (this includes the uncertainty of thermometer reading, CTE, and nominal length. I based my method for calculating this on what I could find in the GUM about coming up with a mathematical model).
All of these uncertainties are expanded uncertainties with a 95% level of confidence.
- Uncertainty due to reproducibility and repeatability: I plan to use the results of a G R&R for this, haven't completed it yet.

I have combined the first three contributors listed above using the root sum of the squares method to obtain a value of 239 μin for the caliper and 35 μin for the micrometer.

I am using tolerance values of 0.001 inches for the caliper and 0.0001 inches for the micrometer, which I believe is what is specified by the manufacturer.

The problem that I am facing is that the micrometer calibration currently has a TUR of 2.82, and although the caliper is currently giving me a TUR of 4.17, I suspect that when the results of the G R&R are included, it could also be lower than 4.

With results like these, I am left with two main questions that I hoping to get some help with:

1) Do my uncertainties budget and associated values seem reasonable?
2) Most perplexing to me, how would anyone be able to calibrate, to a TUR 4:1, a micrometer with a resolution of 0.00005 in and a tolerance of 0.0001 both specified by the manufacturer? The uncertainty due to resolution would take up 23.8 μin, which would give a TUR of 4.2. Although that would be okay on its own, it leaves barely any room for any other source of uncertainty.

I am new to the concept of uncertainty, so any help would be greatly appreciated!!

Thanks!
 
Elsmar Forum Sponsor
Thread starter Similar threads Forum Replies Date
S Uncertainty Budgets - Phase Noise (SSB), Harmonics Measurement Uncertainty (MU) 2
S How to track and manage all uncertainty budgets - Database? Measurement Uncertainty (MU) 3
S Organizing Uncertainty Budgets for different Measurement Equipment Measurement Uncertainty (MU) 4
S A2LA requirements for Electrical Uncertainty Budgets - Measurements with a slope Measurement Uncertainty (MU) 3
B ISO 17025 MU Requirements - Construction Material Testing Lab Uncertainty Budgets ISO 17025 related Discussions 10
L % Uncertainty Budgets - Auditor wants to see my uncertainty budget represented as a % Measurement Uncertainty (MU) 5
M Measurement Uncertainty in Optical Microscopy Measurement Uncertainty (MU) 1
L Uncertainty calculation for an average Measurement Uncertainty (MU) 1
R Determining Uncertainty from Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
B IEC 60601-2-10 - Accuracy of Pulse Parameters - Required Measurement Uncertainty IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
F Missing value of Uncertainty B Measurement Uncertainty (MU) 10
F Issues in Uncertainty Estimation Measurement Uncertainty (MU) 5
F Operator Manual and Type B Uncertainty Measurement Uncertainty (MU) 3
F Learning Uncertainty Budget for Novice - Fluke 5520A Measurement Uncertainty (MU) 1
G Does pitch/increment/resolution of a ruled scale apply to measurement uncertainty as line item? Measurement Uncertainty (MU) 10
R Uncertainty in measurement larger than tolerance Measurement Uncertainty (MU) 2
K ISO 17025:2017 clause 7.6.2 - Performing calibration of its own equipment shall evaluate the measurement uncertainty ISO 17025 related Discussions 6
M Informational US FDA Final Guidance – Consideration of Uncertainty in Making Benefit-Risk Determinations in Medical Device Premarket Approvals, De Novo Classificati Medical Device and FDA Regulations and Standards News 0
A Uncertainty Budget - Externally produced sensor module Measurement Uncertainty (MU) 1
E Discussion between co-worker on tolerance and uncertainty and how to apply it. Thoughts? 17025 ISO 17025 related Discussions 1
G Assigning a calibration tolerance - An x-y coordinate machine - Uncertainty as my verification tolerance General Measurement Device and Calibration Topics 4
G 3 Operator Std. Dev. and uncertainty calculation Measurement Uncertainty (MU) 2
G Reporting measurement uncertainty for custom items Measurement Uncertainty (MU) 2
L Gage R&R for test precision or uncertainty prediction? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
G Uncertainty of staging a short line scale standard on longer measuring machine? Measurement Uncertainty (MU) 4
K Measurement Uncertainty Budget (MU) of for Ultrasonic Thickness gauge Measurement Uncertainty (MU) 1
G NIST SOP 29 - Assignment of Uncertainty - Question General Measurement Device and Calibration Topics 0
M Medical Device News FDA news - 05-09-18 - Draft - Uncertainty in Benefit-Risk Determinations Other US Medical Device Regulations 0
G Can Measurement Machine Bias be part of Uncertainty? General Measurement Device and Calibration Topics 1
G How to include machine error in uncertainty calculations? Measurement Uncertainty (MU) 5
D Difference between uncertainty and expanded uncertainty of measurement General Measurement Device and Calibration Topics 1
M Calibration certificates avowing accuracy beyond the uncertainty limits? Measurement Uncertainty (MU) 7
G ANAB ISO 17025 Accreditation - Uncertainty and systematic error? ISO 17025 related Discussions 6
G How many Uncertainty Measurements for Micrometers and Calipers? Measurement Uncertainty (MU) 3
G What degrees of freedom means in uncertainty budget and how do I set the value Measurement Uncertainty (MU) 2
G Uncertainty Experts - ISO 17025 - If the Distribution is Rectangular Measurement Uncertainty (MU) 2
G Uncertainty Budget Examples for Caliper, Micrometer and Dial Gauge Measurement Uncertainty (MU) 3
P Uncertainty and Significantly Different Means - Buffer Solutions Measurement Uncertainty (MU) 4
S Pressure Gauge Calibration Uncertainty Calibration and Metrology Software and Hardware 5
E Uncertainty of Mean - Test rig that measures water temperatures Measurement Uncertainty (MU) 3
J Internal Laboratory Scope and Measurement Uncertainty (MU) IATF 16949 - Automotive Quality Systems Standard 1
G Manual Procedure with Uncertainty Budgeting for either a Caliper or Micrometer General Measurement Device and Calibration Topics 6
C MU (Measurement Uncertainty) in an Internal Calibration Laboratory Measurement Uncertainty (MU) 1
N How to Convert Micro Volts into Temperature Uncertainty Measurement Uncertainty (MU) 1
N Include homogeneity uncertainty into budget table for thermocouples Measurement Uncertainty (MU) 1
J CMM Uncertainty Calculation Question - Deviations Measurement Uncertainty (MU) 9
M Uncertainty Budget for a Micrometer Measurement Uncertainty (MU) 5
C Uncertainty Trainer in Texas? Measurement Uncertainty (MU) 3
P Purpose of calculating Uncertainty value in calibration study Measurement Uncertainty (MU) 5
C Uncertainty Estimation for Spark Optical Emission Device Measurement Uncertainty (MU) 1

Similar threads

Top Bottom