Final Uncertainty Research Articles

이동로봇의 저비용 위치추정을 위한 효율적인 인공표식 배치기법

인공표식은 이동로봇의 위치추정에서 불확실성을 감소시키기 위해 널리 사용되어 왔다. 또한, 사용되는 인공표식의 수가 증가함에 따라 위치추정 비용이 증가하기 때문에, 인공표식의 효율적 배치를 위한 연구는 핵심적인 이슈중 하나로서 여겨져 왔다. 따라서 본 논문은 운동모델과 센서모델의 불확실성 특성을 고려함으로써 인공표식들을 효율적으로 배치하기 위한 방법을 제안한다. 운동모델과 센서모델은 서로 다른 불확실성 분포를 가지기 때문에, 최종 불확실성은 두 가지 불확실성의 효율적 조합을 통해 크게 감소될 수 있다. 제안한 기법의 유용성은 시뮬레이션 결과에 의해 입증된다. Artificial landmarks have been widely used for reducing the uncertainty in localization of a mobile robot. In addition, research for efficient placement of artificial landmarks has been considered as one of the fundamental issues since the cost of localization is increased with the number of used landmarks. Therefore, this paper proposes a method in which landmarks are efficiently placed by considering the uncertainty characteristics of the motion model and the sensor model. Because two models have different uncertainty distributions, the final uncertainty can be considerably reduced through their efficient combination. The usefulness of the proposed method is demonstrated by simulation results.

Uncertainty evaluation in radon concentration measurement using charcoal canister

Active charcoal detectors are used for testing the concentration of radon in dwellings. The method of measurement is based on radon adsorption on coal and measurement of gamma radiation of radon daughters. The contributions to the final measurement uncertainty are identified, based on the equation for radon activity concentration calculation. Different methods for setting the region of interest for gamma spectrometry of canisters were discussed and evaluated. The obtained radon activity concentration and uncertainties do not depend on peak area determination method.

A methods assessment and recommendations for improving calculations and reducing uncertainties in the determination of 210Po and 210Pb activities in seawater

In marine systems, 210Po and 210Pb disequilibria are being increasingly used to examine oceanic particle formation and export. Here, an updated assessment of current methods for determining 210Po and 210Pb activity in marine samples is provided and includes a complete description of the vast number of calculations and uncertainties associated with Po and Pb loss, decay, and ingrowth during sample processing. First, we summarize the current methods for the determination of 210Po and 210Pb activities in dissolved and particulate seawater samples and recommend areas for improvement. Next, we detail the calculations and associated uncertainties using principles of error propagation, while also accounting for radionuclide ingrowth, decay, and recovery. A spreadsheet reporting these calculations is included as a downloadable Web Appendix. Our analysis provides insight into the contributions of the relative uncertainty for each parameter considered in the calculation of final 210Po and 210Pb activities and gives recommendations on how to obtain the most precise final values. For typical experimental conditions in open seawater, we show that our method allows calculating 210Pb activity with a relative uncertainty of about 7%. However for 210Po activities, the final relative uncertainty is more variable and depends on the 210Po/210Pb activity ratio in the initial sample and the time elapsed between sampling and sample processing. The lowest relative uncertainties on 210Po that can be obtained by this method is 6% and can only be obtained for samples with high 210Po/210Pb activity ratios (>1) that were rapidly processed.

Towards traceability in CO2 line strength measurements by TDLAS at 2.7 µm

Direct tunable diode laser absorption spectroscopy (TDLAS) was combined in this study with metrological principles on the determination of uncertainties to measure the line strengths of the P36e and P34e line of 12C16O2 in the ν1+ν3 band at 2.7µm. Special emphasis was put on traceability and a concise, well-documented uncertainty assessment. We have quantitatively analyzed the uncertainty contributions of different experimental parameters to the uncertainty of the line strength. Establishment of the wavenumber axis and the gas handling procedure proved to be the two major contributors to the final uncertainty. The obtained line strengths at 296K are 1.593×10–20cm/molecule for the P36e and 1.981×10–20cm/molecule for the P34e line, with relative expanded uncertainties of 1.1% and 1.3%, respectively (k=2, corresponding to a 95% confidence level). The measured line strength values are in agreement with literature data (line strengths listed in the HITRAN and GEISA databases), but show an uncertainty, which is at least a factor of 2 lower.

WE-F-105-03: Development of GPMC V2.0, a GPU-Based Monte Carlo Dose Calculation Package for Proton Radiotherapy

Purpose: Monte Carlo (MC) simulation is considered the most accurate method for proton therapy dose calculations. To improve its efficiency, we have previously developed a MC proton dose calculation package, gPMC, on a graphics‐processing unit (GPU) platform. This abstract reports our recent progress towards developing a new version gPMC v2.0, which aims at improving its clinical usability and evaluating it using proton therapy treatment plans. Methods: gPMC v2.0 supports loading source particles from a phase space file. Source particles are first placed to different energy bins according to their energies. Simulation is conducted to transport particles in each bin sequentially. This enforces that particles transported at the same time have similar energies and hence similar computational thread lengths, ensuring computational efficiency in parallel processing. Realistic treatment geometry is supported. A multi‐dose‐counter technique is developed, where multiple dose counters are allocated. Each dose deposition event is randomly assigned to one of the counters. This alleviates memory‐writing conflict problem, when multiple threads attempts to deposit dose to the same voxel. The final dose distribution and statistical uncertainty are obtained based on results at those counters. gPMC v2.0 also supports scoring dose‐to‐water. We have tested the new version in head‐and‐neck patient cases. Results: Computation time is ∼5 seconds for a typical patient case, where 2.1 million protons in a phase space file are simulated. It takes additional ∼8 seconds to load the phase space file. The dose distribution agrees well with that from TOPAS/Geant4. Inside a region of interest defined by the 50% iso‐dose line, gamma passing rate is ∼98% (3mm/3%) and ∼95% (2mm/2%) compared with TOPAS/Geant4 Result. The average relative uncertainty is 1.1%. Conclusion: gPMC has achieved accuracy and efficiency well beyond what was previously accomplished. It supports the recalculation of proton therapy treatment plans, making it feasible for routine clinical applications. This work is supported in part by the University of California Lab Fees Research Program and in part by R01 CA140735

The experimental determination and evaluation of the spectral indices of the IPEN/MB-01 reactor for the IRPhE project

New experimental results for the spectral indices of the IPEN/MB-01 reactor are presented in this work. The experimental approach considers a new technique for the 28ρ case which does not require any sort of calculated correction factors. This aspect gave to the IPEN/MB-01 experiment an excellent quality and free of possible bias due to these calculated correction factors. The uncertainty analysis show, even considering the uncertainties of the geometric and material data of the facility, that the final uncertainties are small enough and well understood for a benchmark problem. The experiment was evaluated and included in the IRPhE handbook. The theory/experiment comparison reveals that there is considerable progress in the 238U nuclear data for application in thermal reactors. The theory/experiment comparison employs the nuclear data libraries ENDF/B-VII.0, ENDF/B-VI.8, JEF3.1, and JENDL3.3 and reveals an excellent agreement for the spectral index 28ρ* independently of the nuclear data library considered; aspect never found before in several other comparisons. The long term overprediction of the 238U neutron epithermal capture appears to be eliminated with the improvements in the recent nuclear data libraries. The experimental performed at the IPEN/MB-01 reactor supports the changes in the 238U nuclear data incorporated in ENDF/B-VII.0 as well as in the other libraries studied in this work. The theory/experiment comparison of 25δ* and (C8/F)ept show that these spectral indices are in general slightly overpredicted, thus suggesting that the thermal fission cross section of 235U might be a little bit underestimated. The overall analysis of the theory/experiment comparisons show the excellent applicability of ENDF/B-VII.0 for thermal reactors fuelled with slightly enriched uranium.

Processing Dependent Systematic Contributions to Measurement Uncertainty

In the measurement field, the correlation of two uncertainty contributions is a form of probabilistic association that can significantly affect the final uncertainty associated to the measurement result. The Guide to the expression of uncertainty in measurement recommends a mathematical approach to deal with correlated random contributions to measurement uncertainty. A similar kind of association, or dependence, can characterize also different systematic contributions to uncertainty and should be taken into account when evaluating their effect on the final measurement uncertainty. This paper discusses a new approach to handle such systematic contributions when they are represented by symmetric possibility distributions (PDs) of the same shape. This method allows one to build the joint PD of two systematic contributions, both dependent and independent, and propagate them through a generic measurement function.

Reporting uncertainties in measurement: what approach should be followed?

Much of the work of a scientist or engineer involves taking measurements. For example, a radiation oncology medical physicist measures the absorbed dose in a water phantom. However any measurement has some limit in the accuracy of the final value you obtain. This is due to limits in the accuracy of the measuring equipment, any bias in the measurements, calibration issues or simple mistakes you make. All of these contribute to an uncertainty in the value of the parameter you are measuring. For example, the absorbed dose of radiation from a linear accelerator can be measured in a water phantom using a well characterised ionisation chamber. In this particular case of radiation dose measurement, there will be uncertainties due to the equipment consisting of an ionisation chamber, electrometer and the water phantom. There will also be uncertainties in the setup of the equipment, the linear accelerator. Traditionally these uncertainties are characterised as random errors or systematic errors. Random errors can be minimised by taking multiple measurements while the reduction of systematic uncertainties requires a good understanding of the equipment. Systematic errors are often ‘‘fixed’’ by application of some calibration factor or may be even missed. The method used to determine the uncertainty of a measurement is widely varied. For example, you can repeat the measurements a number of times usually between 3 and 5, and from this calculate the standard deviation. A more systematic approach is to determine random and systematic errors and summate these together to give the final uncertainty in your parameter. This takes a bit more time and requires that you have a good understanding of your equipment. Finally, you can ignore your errors, assume your equipment is working correctly and just quote your results. A review of published papers in any medical physics or biomedical engineering journal will show a similar variation in reporting of uncertainties. This can give the impression of a much lower uncertainty in your measurements. For example, the IAEA TRS 398 dosimetry protocol reports that the estimated relative uncertainty in the dose calibration of megavoltage X-ray beams is ±1.5 % [1]. Therefore any absolute dose measurements using these X-ray beams must have an uncertainty larger than this. There is a more uniform approach for uncertainty analysis as prescribed by the International Organization for Standardization (ISO). The ISO has published a document called the ‘‘Guide to the expression of uncertainties in R. Hill (&) Department of Radiation Oncology, Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia e-mail: robin.hill@email.cs.nsw.gov.au

“Analyte” is frequently used as synonym for “measurand”: is that correct?

In a measurement, a most basic concept is ‘‘measurand.’’When starting to draft a plan for a process called mea-surement, we must clearly specify the goal of the process.That goal must have been discussed with the end user(frequently called the customer) on beforehand. Agreeingon such a goal and respecting this agreement will ensurethat the result obtained at the end of the process as carriedout by the analyst, is fit for the intended use [1] of the resultby the end user. The product of a discussion between theend user of the result and the analyst is about what is thegoal of the process. Thereby the end user should not have toworry about how the analyst performs the process: that iswhat the end user pays the analyst for. Thus, the analystmust make sure that the measurement result (s)he obtains atthe end of the process is clearly related to the goal (s)he hasagreed with the end user. All intermediate steps that need tobe taken during the process, including whatever chemicaloperations such as weighings, dissolutions, separations,chemical transformations, preparation of samples suitablefor introduction into whatever type of spectrometer, mea-surements of other input quantities (see entry 2.50 in [2])into the measurement function (see entry 2.49 in [2]), etc.,deemed necessary by the analyst to reach the goal agreedwith the end user, ultimately are the analyst’s choice anddecision, not the end user’s. The analyst is in control ofassigning the value (with associated measurement uncer-tainty) to the measurement result [3]. The intermediatesteps, important as they may—or because sometimes theyare so important—pertain to the answer to the question howthe goal agreed with the end user, is attained by the analyst.This logic is the rationale for the fundamental change inthe definition of ‘‘measurand’’ in the 3rd edition of theInternational Vocabulary of Metrology—VIM [2].It is important to note that the ‘‘quantity subject tomeasurement,’’ the former definition of ‘‘measurand’’ inthe VIM, 2nd edition [4], was very different from the newdefinition in the 3rd edition of the VIM: ‘‘quantity intendedto be measured.’’ The definition in the 3rd edition is ofgreat help in chemistry, as chemistry-specific intermediatesteps now become part of the process of measurement,possibly including measurements performed on interme-diate chemical species showing up in the process (inclinical chemistry, such species is called component orchemical substance [6] and its meaning is considered to beoverlapping with the meaning of the term analyte). Thathas the consequence that all chemical preparation work ona sample in view of obtaining a measured value (withassociated uncertainty) for the intended measurement resultof an a priori specified quantity (the measurand) in theoriginal material as well as any desired transformation of achemical species and measurements of its properties,become an inherent part of the planned process. That alsohas the consequence that the uncertainty naturally associ-ated with each step in that chemical preparation work aswell as with any transformation process will have to beincluded in the uncertainty budget (see entry 2.33 in [2]) ofthe final measurement result for the measurand. That willincrease this final uncertainty, making it larger than just,for example, the measurement of electric current(s) in aninstrumental measuring system (see entry 3.2 in [2]). Butsuch a measurement uncertainty will correspond to a morerealistic measure of ‘‘doubt’’ [5] about the measurement

Estimation of Complex and Linear Uncertainities in S-Parameter Measurements for Metrology Applications

The present paper aims to develop a uniform procedure of estimating uncertainty components in VNA measurements whether in complex or linear units. The individual response of each uncertainty components have been studied in the frequency range 1 to 18 GHz, which are applicable for one-port and two-port measurements. The Vector network analyser (VNA) measurements are performed to assign an overall uncertainty for the respective measuring parameter in terms of comp lex and linear units for coaxial step attenuator, fixed attenuator and mis match. These measurements are then verified through the primary and transfer standards of the attenuation and impedance parameters and thus the traceability of the VNA measurements is established. Finally, the outcome of co mplete study has been presented as VNA measurements based new calibrat ion and measurement capabilit ies (CM Cs) for NPL, India. It has shown that the final combined uncertainty is found same or nearby by obtaining from uncertainty components either in complex or in linear units. Thus, this paper reports the estimation of VNA measurement uncertainties for various parameters as per the requirements of IS O/IEC 17025:2005 standard.

The PTB primary standard for the absorbed-dose to water for I-125 interstitial brachytherapy sources

The German national metrology institute (PTB) developed a primary standard in terms of absorbed-dose to water Dw for low-energy interstitial brachytherapy sources, which is based on an extrapolation chamber in a phantom of water-equivalent material.The method to determine Dw from extrapolation chamber measurements has been newly developed and is already described in the literature. With the chamber the absorbed-dose at 30 cm distance from the source is measured and the quantity is converted into the desired quantity, the absorbed-dose to water measured at 1 cm distance perpendicular to the source axis.In this paper, a synthesis of the work done within the EMRP Project: ‘TP2.JRP6: Increasing Cancer Treatment Efficacy Using 3D Brachytherapy’ is given and the final results and the final uncertainty budget are presented. Furthermore, an experimentally determined dose-rate constant for this seed type (BEBIG Symmetra I25.S16) is given based on the measurement of four different instances.

Bayesian inference from photometric redshift surveys

We show how to enhance the redshift accuracy of surveys consisting of tracers with highly uncertain positions along the line of sight. Photometric surveys with redshift uncertainty delta_z ~ 0.03 can yield final redshift uncertainties of delta_z_f ~ 0.003 in high density regions. This increased redshift precision is achieved by imposing an isotropy and 2-point correlation prior in a Bayesian analysis and is completely independent of the process that estimates the photometric redshift. As a byproduct, the method also infers the three dimensional density field, essentially super-resolving high density regions in redshift space. Our method fully takes into account the survey mask and selection function. It uses a simplified Poissonian picture of galaxy formation, relating preferred locations of galaxies to regions of higher density in the matter field. The method quantifies the remaining uncertainties in the three dimensional density field and the true radial locations of galaxies by generating samples that are constrained by the survey data. The exploration of this high dimensional, non-Gaussian joint posterior is made feasible using multiple-block Metropolis-Hastings sampling. We demonstrate the performance of our implementation on a simulation containing 2.0 x 10^7 galaxies. These results bear out the promise of Bayesian analysis for upcoming photometric large scale structure surveys with tens of millions of galaxies.

Quantifying uncertainty in LCA-modelling of waste management systems

Uncertainty analysis in LCA studies has been subject to major progress over the last years. In the context of waste management, various methods have been implemented but a systematic method for uncertainty analysis of waste-LCA studies is lacking. The objective of this paper is (1) to present the sources of uncertainty specifically inherent to waste-LCA studies, (2) to select and apply several methods for uncertainty analysis and (3) to develop a general framework for quantitative uncertainty assessment of LCA of waste management systems. The suggested method is a sequence of four steps combining the selected methods: (Step 1) a sensitivity analysis evaluating the sensitivities of the results with respect to the input uncertainties, (Step 2) an uncertainty propagation providing appropriate tools for representing uncertainties and calculating the overall uncertainty of the model results, (Step 3) an uncertainty contribution analysis quantifying the contribution of each parameter uncertainty to the final uncertainty and (Step 4) as a new approach, a combined sensitivity analysis providing a visualisation of the shift in the ranking of different options due to variations of selected key parameters. This tiered approach optimises the resources available to LCA practitioners by only propagating the most influential uncertainties.

Analysis of Key Comparisons Incorporating Knowledge About Bias

A method is proposed for analyzing key comparison data. It is based on the assumption that each laboratory participating in the comparison exercise obtains independent and consistent estimates of the measurand and that, in addition, each laboratory provides an estimate of the quantity that collects all systematic effects that the laboratory took into account. The unknown value of the latter quantity, subtracted from its estimate, is defined as the laboratory's bias. The uncertainties associated with the estimates of the measurand and with the vanishing biases' estimates are also assumed to be reported. In this paper, we show that the information provided in this way may be of help for judging the performances of the laboratories in their correction of systematic effects. This is done by developing formulas for the final (consensus) estimates and uncertainties of the measurand and of the biases. Formulas for the final estimates and uncertainties of the pairwise differences between the biases are also developed. An example involving simulated key comparison data makes apparent the benefits of the proposed approach.

Characterization of arbitrary waveform generator by low resolution and oversampling signal acquisition

The paper deals with two relevant aspects of output section characterization of an Arbitrary Waveform Generator (AWG). The first concerns the difficulty of acquiring the output signal from Analog to Digital Converter with both higher linearity and resolution than the AWG under test. The proposed solution makes the problem simpler: oversampling with lower resolution. This result is achieved by means of an acquisition procedure to reconstruct the AWG output signal based on the zero crossing time sequence. Since the reconstructed signal is not uniformly sampled, proper algorithms in the time and frequency domain are proposed to evaluate also the dynamic parameters. The second is linked to the first and concerns the difficulty of evaluating the transfer characteristic. Indeed, the correspondence between the input code and the output sample of the AWG is avoided due to the acquisition procedure proposed, and the AWG operating mode. The proposed procedure allows the input code to be correlated with the corresponding sample of the output signal. It operates in iterative modality to achieve the valid statistical occurrences of the codes. Indeed, owing to the oversampling and the memory size of the acquisition hardware system, the number of samples could be lower than the number of expected output levels of the AWG. Numerical tests have allowed validation of the proposed iterative procedure in the case where the transfer characteristic is affected by nonlinearity, missing code and quantization noise. The experimental setup of the proposed procedure has allowed assessment of: (i) the effectiveness of the iterative procedure in evaluating the transfer characteristic; (ii) the lower resolution of the acquisition hardware system with respect to the direct acquisition. On the basis of the error caused by the numerical procedure and the noise introduced by each device of the experimental set up, the lower bound of the final uncertainty is deduced.

Comprehensive analysis of proton range uncertainties related to patient stopping-power-ratio estimation using the stoichiometric calibration

The purpose of this study was to analyze factors affecting proton stopping-power-ratio (SPR) estimations and range uncertainties in proton therapy planning using the standard stoichiometric calibration. The SPR uncertainties were grouped into five categories according to their origins and then estimated based on previously published reports or measurements. For the first time, the impact of tissue composition variations on SPR estimation was assessed and the uncertainty estimates of each category were determined for low-density (lung), soft, and high-density (bone) tissues. A composite, 95th percentile water-equivalent-thickness uncertainty was calculated from multiple beam directions in 15 patients with various types of cancer undergoing proton therapy. The SPR uncertainties (1σ) were quite different (ranging from 1.6% to 5.0%) in different tissue groups, although the final combined uncertainty (95th percentile) for different treatment sites was fairly consistent at 3.0–3.4%, primarily because soft tissue is the dominant tissue type in the human body. The dominant contributing factor for uncertainties in soft tissues was the degeneracy of Hounsfield numbers in the presence of tissue composition variations. To reduce the overall uncertainties in SPR estimation, the use of dual-energy computed tomography is suggested. The values recommended in this study based on typical treatment sites and a small group of patients roughly agree with the commonly referenced value (3.5%) used for margin design. By using tissue-specific range uncertainties, one could estimate the beam-specific range margin by accounting for different types and amounts of tissues along a beam, which may allow for customization of range uncertainty for each beam direction.

Uncertainty Modelling to Evaluate Nitrogen Balances As a Tool to Determine N2 and N2O Formation in Ammonia Bioscrubbers

Biological scrubbers aim at reducing gaseous ammonia emissions by transferring it to a water phase followed by conversion to nitrite and nitrate. A small part of the removed nitrogen may be emitted as N2 and N2O produced as a result of denitrification processes. Due to the large greenhouse warming potential of N2O, even a small emission could be a point of concern. Determining these N losses in form of N2 and N2O via nitrogen balance is an alternative, but little is known about the uncertainty associated to this method. The main aim of this work was to develop an uncertainty model that evaluated N-balances in biological scrubbers in terms of result uncertainty. Secondary objectives were to provide a methodology to determine individual uncertainties involved, and to conduct a sensitivity analysis to identify the main contributors to the final uncertainty. For a defined scenario (biotrickling scrubber, 70% NH3 removal; 5% of inlet N-NH3 lost as N2 and N2O), the standard uncertainty expressed in relative terms of the average was 132% (released N in form of N2 and N2O). Main contributors to the final uncertainty were airflow rate and water volume in the scrubber basin. Uncertainty of the measurements of gaseous NH3 concentrations and N compounds in water had a reduced effect on the final uncertainty. Based on these results, N balances are not recommended to evaluate N2 and N2O formation in biological scrubbers, at least for the conditions considered in this work.

Analysis of uncertainties affecting the Monte Carlo simulation of a neutron multiplicity counter

Abstract When applying numerical simulation to physical problems it is important to be able to clearly understand the quality that can be reached and the uncertainty associated with the modelling. In this paper we will deal with the Monte Carlo simulation of neutron coincidence and multiplicity counters. These instruments are intensively used in nuclear safeguards for the measurement and verification of the mass of fissile materials in nuclear installations. Their numerical simulation, either for detector design or for numerical calibration, is now used more and more frequently as support to inspections. Several benchmark exercises have been organised in order to assess the capabilities of Monte Carlo simulation to correctly predict realistic practical cases in neutron coincidence and multiplicity counting. Nevertheless most of them allowed reaching conclusions only on the overall uncertainties associated to the modelling through the comparison between calculated and measured integral data. In this paper we aim to analyse more deeply the sources of these uncertainties, separating the different possible causes and analysing parametrically the individual factors. We will include influencing factors deriving from the physical model of the detector, of the acquisition electronics, of the sample and from the nuclear data. The final total uncertainties are consistent with the results of the integral benchmarks.

The precision of humidity in GNSS tomography

The GNSS signal passing through the layers of the atmosphere, including troposphere is subjected to many effects. One of the effect is a change of signal phase propagation speed due to the change of density. The large fluctuation of density is due to water vapor content - the most important greenhouse gas. The ground GNSS tomography is a tool to obtain the wet refractivity of the discrete model above the network of receivers. The wet refractivity could be converted into water vapor partial pressure, using the additional temperature information. This paper presents rigorous approach to obtain uncertainties of the final product - water vapor partial pressure in the voxel. All factors influencing the final uncertainty has been taken into account, mainly uncertainty of: Zenith Troposphere Delay, pressure, antenna phase center height, satellite elevation angle, mapping function, tomography solution and temperature. The analyzed error budget shows, great influence of cofactor matrix topology on tomography solution uncertainty. It is also shown that ground GNSS tomography is feasible to obtain water vapor partial pressure in the troposphere up to 0.5hPa so in average 6km above the ground.

Development and Uncertainty Analysis of an Automatic Testing System for Diffusion Pump Performance

Abstract A newly developed automatic testing system used in laboratory for diffusion pump performance measurement is introduced in this paper. By using two optical fiber sensors to indicate the oil level in glass-buret and a needle valve driven by a stepper motor to regulate the pressure in the test dome, the system can automatically test the ultimate pressure and pumping speed of a diffusion pump in accordance with ISO 1608. The uncertainty analysis theory is applied to analyze pumping speed measurement results. Based on the test principle and system structure, it is studied how much influence each component and test step contributes to the final uncertainty. According to differential method, the mathematical model for systematic uncertainty transfer function is established. Finally, by case study, combined uncertainties of manual operation and automatic operation are compared with each other (6.11% and 5.87% respectively). The reasonableness and practicality of this newly developed automatic testing system is proved.