Evaluation of uncertainty of caliper
I. Assessment, environmental conditions and overview
1, model: 0-150 mm;
2. Uncertainty of gauge block: 0.00014mm.
3. Environmental conditions: the temperature is (20 2)℃ and the humidity is 40%-75%;
4. Basis of measurement method: According to JJG30-2002 universal caliper verification regulations, select the corresponding measurement and test methods. Measure the gauge block n( n = 7) times.
Second, the main sources and analysis of uncertainty
The measurement is carried out under standard conditions, and the linear expansion coefficient caused by the influence of temperature and humidity is very small and almost constant, which can be ignored, and the uncertainty component can be ignored. Therefore, the uncertainty of coordinate measuring instrument measurement results mainly comes from the following aspects:
1, repeatability of measurement;
2. Uncertainty of gauge block;
Thirdly, the mathematical model of uncertainty is established
W = W′
Where w is the standard size of the gauge block.
W '- actual measured size
Evaluation of standard uncertainty of each component
1. Calipers repeatedly determine the component uncertainty U A.
Continuously and repeatedly measure and record the position value of the measured functional gauge, and the results are listed in table 1.
Table 1 function gauge position measurement and calculation data table
n 1 2 3 4 5 6 7
Xmi (mm) 99.99100.00100.00 99100.00100.06 5438+0100.00.
(mm)
99.72
Average value:
= 99.72 mm
According to Bessel formula, there is uncertainty introduced by repeated determination.
ua =×= 0. 1 138um = 0.0 1 138mm
2. Uncertainty ub of gauge block
Ub = 0.000014mm
Fourthly, the uncertainty of synthesis standard.
Uc = = = = 0.02mm
Verb (abbreviation of verb) expands uncertainty uc
If k=2, then u = u = 2uc = 2× 0.2mm = 0.4mm.
Report on measurement uncertainty of intransitive verbs
The expanded uncertainty of calipers is U=0.02mm, which is obtained by U=2uc and k=2.
Preparation: Date: Approval: Date: