1. Improving uncertainty of strain gauge bridge standardsMiha Hiti, 2018, published scientific conference contribution Abstract: The article proposes a procedure for calibration of strain gauge bridge standards with improved relative calibration uncertainty. In contrast to a typical calibration with voltage ratio standards or comparison calibration with other bridge standards, the proposed procedure uses a calibrated reference bridge amplifier, additionally evaluated using combinatorial calibration technique to improve its calibration uncertainty. The resulting uncertainty of ratio steps referenced to zero ratio step is lower than the traditional uncertainty achieved through direct independent traceability to mVV−1 ratio values. The proposed procedure enables direct application of the calibrated bridge standard values with low relative uncertainty for calibration of bridge amplifiers, without the need for additional combinatorial evaluation of each individual bridge amplifier.
Keywords: voltage ratio, linearity check, bridge standard, calibration
Published in DiRROS: 05.04.2024; Views: 85; Downloads: 56
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2. Analysis of loading profile effect on testing machine calibration resultsMiha Hiti, 2021, original scientific article Abstract: The paper presents an evaluation of the loading profile effect on the testing machine calibration. First, a 20 kN force transducer was calibrated in a force calibration machine. This transducer was then used for a number of calibration runs in a 600 kN material testing machine where the time step interval of the same loading profile was varied from 120 s to 0 s. Results show good agreement for most of the range but highlight an increasing error due to synchronization and filtering issues in measured signals when approaching very short step intervals and continuous loading.
Keywords: force calibration, loading profile, measurement uncertainty, continuous loading
Published in DiRROS: 20.12.2023; Views: 203; Downloads: 108
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3. Compensation of synchronization error effect in testing machine calibrationMiha Hiti, 2021, original scientific article Abstract: The paper presents an evaluation of synchronization issues when performing material testing machine calibration using continuous loading. A procedure for the compensation of a rangewide error in calibrated force values is proposed based on a correction factor determined from static and transient errors difference at a chosen force step. The procedure was applied for a calibration of a testing machine with a 20 kN force transducer and 200 N/s to 2000 N/s loading rates. The results show good performance of the compensation technique, reducing calibration errors to below 1% in non-synchronized signals even under unknown filter and delay setting.
Keywords: force calibration, loading profile, measurement uncertainty, continuous loading
Published in DiRROS: 20.12.2023; Views: 183; Downloads: 91
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4. Validation of combinatorial evaluation of strain-gauge amplifier linearityMiha Hiti, 2020, original scientific article Abstract: This paper describes a validation of a combinatorial calibration technique based calibration procedure for strain-gauge amplifier calibration. The deviation between two strain-gauge amplifiers at calibration using the combinatorial technique is compared to the deviation between the same two amplifiers at calibration on a force calibration machine as a transducer-amplifier chain under unchanged conditions, serving as an amplifier linearity comparator. This enables the validation to be confirmed with a suitable expanded measurement uncertainty of 3 nV/V.
Keywords: strain-gauge amplifier, calibration, combinatorial technique, validation
Published in DiRROS: 21.08.2023; Views: 293; Downloads: 104
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5. Investigation of the British pendulum calibration uncertainty by Monte Carlo simulationVid Primožič, Miha Hiti, 2022, original scientific article Abstract: The paper presents the evaluation of the calibration uncertainty of the British pendulum slip resistance tester using Monte Carlo simulation method. A mathematical model was produced which describes pendulum behavior based on its calibration parameters. The Monte Carlo simulation, programmed in Python, was used for simulating the effect of each of the calibration parameters adjustment within their tolerance intervals, with uniform and triangular probability distribution. Four different tolerance limits were compared: limits from a current international standard, a proposition with reduced limits from recent literature, and two novel propositions, one with reduced but easily achievable limits, and a second one for best practically achievable limits. The results of the simulation show a fundamental standard uncertainty contribution of about 2.8% for pendulum calibration according to current standard limits. Furthermore, they suggest a possible improvement to 0.5%–0.7% as its best practical direct calibration standard uncertainty for reduced limits.
Keywords: British pendulum, simulacija, Monte Carlo, merilna negotovost, odprti dostop
Published in DiRROS: 20.06.2023; Views: 323; Downloads: 181
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