Uncertainty of staging a short line scale standard on longer measuring machine?


Involved In Discussions
I have a measuring machine that measures up to 1000mm in length, but my traceable standard is only 400mm long. When I calibrate I align the standard parallel , start at the left side and measure every 10mm to check for accuracy deviations. I then move the scale to the right, overlapping approx. 20mm, align it parallel and measure from the left end of the scale (every 10mm) to the end at 400mm. Then again , covering the full 1000mm of measurement range.

My question is; how do I include the multiple use of this scale into my uncertainty calculation.

I think I need to include the following in my uncert calc. for each range; (in addition to repeatability, temperature effects, etc.)
What am I forgetting about (or don't know!) about staging a line scale standard like this?

0-400 mm
uncert of std.

400-780 mm
2x uncert of std
max error found in 0-400 mm range

780-1000 mm
3x uncert of std.
max error found in 0-400 mm range
measurement uncertainty for measuring error in 0-400 mm
max error found in 400-780 mm range
measurement uncertainty for measuring error in 400-780 mm

Thanks to all!
Elsmar Forum Sponsor


Trusted Information Resource
If I am picturing this correctly, every time you move your scale you start with a new reference on your measuring machine.
If you do that you are only checking linearity for a 400 mm span, not for the full 1000 mm range.
Since each 400 mm segment is measured independently you would only be using the uncertainty of the standard, not multiples of it.
But you will not be making a 1000 mm linearity measurement.


Involved In Discussions
Yes, I move the scale each time, but the starting point of each move is overlapping the previously measured zone. So, the accuracy for range 2 and range 3 are dependent on the uncertainty and any bias seen in all previous ranges. Does accounting for the previous bias then get me to the full 1000 mm? If not why not?


Trusted Information Resource
What you have here is a very conservative estimation of the 1000 mm uncertainty.
Simple algebraic addition of the contributors will give you the largest uncertainty value. If you can live with the larger uncertainty then you are fine.
If you need to reduce the uncertainty then you will need to take steps to determine any correlations that can be combined to reduce the total uncertainty.
Thread starter Similar threads Forum Replies Date
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
S Uncertainty Budgets - Phase Noise (SSB), Harmonics 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
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
W Dimensional Measurement of 10% accuracy and 25% uncertainty standard General Measurement Device and Calibration Topics 6
B Measurement Uncertainty using Minitab Measurement Uncertainty (MU) 2
J Uncertainty budget for IR thermometry at high T - 1000 - 1500?C Measurement Uncertainty (MU) 1
N Understanding the absolute uncertainty specification for a Fluke 5500A Measurement Uncertainty (MU) 3
M Help with uncertainty calculation in the calibration of a Pyrogen Test Processor Measurement Uncertainty (MU) 7
S How to track and manage all uncertainty budgets - Database? Measurement Uncertainty (MU) 3

Similar threads

Top Bottom