How to Calculate the Resolution of a Load Cell Per Section 4.14 of JCGM 200:2012, Resolution is the “smallest change in a quantity being measured that causes a perceptible change in the corresponding indication.” Over the years, this simple definition has become a topic of confusion in the metrology community. We are hoping to simplify […]
The Importance of Considering Reproducibility in the Measurement Process Uncertainty - Intro Most people in the metrology community will agree that a calibration laboratory's ability to reproduce measurement results belongs in an uncertainty budget. Several Accreditation Bodies require reproducibility to be at least considered as part of a calibration laboratory's Calibration and Measurement Capability (CMC). […]
Why a 4:1 TUR is Not Enough: The Importance of Analyzing the Probability of False Accept Risk Figure 1 Graph Showing Method 5 Acceptance Limits Several organizations and publications reference the use of a 4:1 Test Uncertainty Ratio (TUR). Some standards even reference a TUR requirement greater than or equal to 4:1. The question to […]
How to Calculate the Uncertainty of a Deadweight Primary Standard Machine Figure 1: Morehouse 1,000 lbf automated deadweight machine Deadweight Force Machines or Primary Force Standard (CMCs as low as 0.001 % of applied force) – a deadweight force applied directly without intervening mechanisms such as levers, hydraulic multipliers, or the like, whose mass has […]
Load Cell Stability – How It Can Kill Your Uncertainty Budget Load cells are a combination of metal, strain gauges, adhesive, and more. Like humans, every measuring instrument is subject to aging. Load cells age from mechanical stress or fatigue, and over time this ensures that there will be some instability in the system. Some […]
Cosine Error Should be Considered in any Torque Measurement Process ISO/IEC 17025 When Calculating Torque Measurement Error Cosine Error should be considered A ‘vector’ is known as a quantity that is defined by its size and direction. Every time the effect of a known force is evaluated on a static or dynamic system, all applied, […]
Guidance on Uncertainty Budgets for Force Measuring Devices Part 4. Calculating Uncertainty for ISO 376 Uncertainty Analysis ISO 376 Uncertainty Analysis Introduction: All calibration laboratories accredited to ISO/IEC 17025 are required to submit uncertainty calculations for the Calibration and Measurement Capability uncertainty claims included in the scope of accreditation. The assumptions made for the determination […]
Guidance on Uncertainty Budgets for Force Measuring Devices Part 3. Calculating Uncertainty for Force Measuring Devices for Measurement or Calculating Uncertainty for Force Measuring Devices Background: Currently, there are discrepancies regarding what is acceptable for a force calibration uncertainty budget. A common mistake is to include too many lines from the load cell specification sheet. For […]
Guidance on Uncertainty Budgets for Force Measuring Devices Part 2. Calculating Uncertainty in Accordance with ASTM E74 Standard Calculating Uncertainty in accordance with ASTM E74 Standard Background: ASTM E74 Standard Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing Machines is the standard followed by many in North America for the […]
Guidance on Uncertainty Budgets for Force Measuring Devices Part 1. Why Do We Need a Solid Guidance Document? Uncertainty Budgets for Force Measuring Devices Introduction: All calibration laboratories accredited to ISO/IEC 17025 must submit uncertainty calculations for the Calibration and Measurement Capability uncertainty claims included in the scope of accreditation. The assumptions made to determine the uncertainty […]
What Happens When You Overshoot a Test Point? Various calibration laboratories use hydraulic, screw, and other force calibration machines where it is difficult not to overshoot a test point. By talking about overshooting a test point, we are referring to loading past the desired point and then letting the creep in the hydraulic system naturally […]
The Top 5 Costly Force Measurement Mistakes #1 of 5 Costly force measurement mistakes Most calibration laboratories will say a device is "In Tolerance" without considering the uncertainty of their measurement process. This equates to you not using a calibration laboratory that has standards to meet your needs and accounts for measurement risk properly. Most […]
