Good Measurement Capability Research Articles

VALIDITY AND RELIABILITY OF MULTIPLE-CHOICE BIOLOGY TEST: A RASCH ANALYSIS PERSPECTIVE

Concerns about the accuracy of multiple-choice tests for assessing biology knowledge have led to an increased emphasis on validating these tests using sophisticated analytical techniques like Rasch analysis. A 22-item multiple-choice cell division test was administered to 35 Form Four students in Kota Kinabalu, Sabah and validated through Rasch analysis, with MNSQ item values falling within the acceptable range of 0.79 to 1.24 logit. Additionally, the ZSTD components of Infit and Outfit showed favourable logit values aligning positively with the intended measures. Overall, the results indicated that item fits were within an acceptable range and PTMEA-CORR values measured what was intended to assess. Meanwhile, the Cronbach’s alpha was a good value at 0.65, with person reliability of 0.72 and item reliability of 0.76. The person separation was observed at a value of 1.62 while the item separation considered acceptable at a value of 1.80; indicating good measurement capability which supports its use in evaluating students' comprehension of biological concepts. Applying the Rasch model demonstrated consistent and reliable test enabling assessment of students' achievement in biology; contributing towards continuous improvement in teaching and learning biology.

Fiber Bragg Grating Displacement Sensor with High Abrasion Resistance for a Steel Spring Floating Slab Damping Track.

This paper presents a fiber Bragg grating (FBG) displacement sensor with high abrasion resistance for displacement monitoring of a steel spring floating slab damping track. A wedge-shaped sliding block and an equal-strength beam form a conversion mechanism to transfer displacement to the deflection of the beam, and the deflection-induced strain is exerted on two FBGs. A special linear guide rail-slider and a precision rolling bearing have been adopted onto the conversion mechanism, which turned sliding friction into rolling friction and thus significantly reduced the friction during frequent alternating displacement measuring. Sensing principle and the corresponding theoretical derivation have been demonstrated. Experiment results show that the sensor has a sensitivity of 34.32 pm/mm and a high resolution of 0.0029 mm within a measurement range of 0~90 mm. Besides, the sensor has also a good measurement capability for micro-displacement within a range of 0~3 mm. The repeatability error and hysteresis error are 1.416% and 0.323%, respectively. Good creep resistance and high abrasion resistance for alternating displacement measurement have also been presented by a performance test. These excellent performances satisfy the requirements of high precision and long-term stability in structural health monitoring for machinery equipment and civil engineering, especially in the displacement monitoring of a floating slab damping track.

Statistical analysis on experimental calibration data for flowmeters in pressure pipes

This paper shows a statistical analysis on experimental calibration data for flowmeters (i.e.: electromagnetic, ultrasonic, turbine flowmeters) in pressure pipes. The experimental calibration data set consists of the whole archive of the calibration tests carried out on 246 flowmeters from January 2001 to October 2015 at Settore Portate of Laboratorio di Idraulica “G. Fantoli” of Politecnico di Milano, that is accredited as LAT 104 for a flow range between 3 l/s and 80 l/s, with a certified Calibration and Measurement Capability (CMC) - formerly known as Best Measurement Capability (BMC) - equal to 0.2%. The data set is split into three subsets, respectively consisting in: 94 electromagnetic, 83 ultrasonic and 69 turbine flowmeters; each subset is analysed separately from the others, but then a final comparison is carried out. In particular, the main focus of the statistical analysis is the correction C, that is the difference between the flow rate Q measured by the calibration facility (through the accredited procedures and the certified reference specimen) minus the flow rate QM contemporarily recorded by the flowmeter under calibration, expressed as a percentage of the same QM.

A calibration setting with uncertainty measurements for passive/active radon monitors using flow-through source type

Based upon the steady flow method, a setting has been introduced for fast calibration of almost all types of active and passive radon detectors. In this method, a traceable radon reference flow-through sources is connected to a portable rectangular cubic transparent chamber (volume of 50L) which is completely sealed and has 6 valves on its sides. The initializing calibration times are less than 150min by this chamber. The radon concentration in the chamber is in consistent with the source activity. The Best Measurement Capability (BMC) of the method has been calculated less than 5% at 68% confidence level. As well by using grab-sampling method, the difference of radon concentration of different points in the chamber was measured less than 1.2%. So the flow-through sources can be developed for a fast calibration of almost all types of the radon monitors with an acceptable uncertainty using this calibration setting.

Evaluation of Calibration Laboratories Performance

One of the main goals of interlaboratory comparisons (ILCs) is the evaluation of the laboratories performance for the routine calibrations they perform for the clients. In the frame of Accreditation of Laboratories, the national accreditation boards (NABs) in collaboration with the national metrology institutes (NMIs) organize the ILCs needed to comply with the requirements of the international accreditation organizations. In order that an ILC is a reliable tool for a laboratory to validate its best measurement capability (BMC), it is needed that the NMI (reference laboratory) provides a better traveling standard—in terms of accuracy class or uncertainty—than the laboratories BMCs. Although this is the general situation, there are cases where the NABs ask the NMIs to evaluate the performance of the accredited laboratories when calibrating industrial measuring instruments. The aim of this article is to discuss the existing approaches for the evaluation of ILCs and propose a basis for the validation of the laboratories measurement capabilities. An example is drafted with the evaluation of the results of mercury-in-glass thermometers ILC with 12 participant laboratories.

Diesel engine dynamometer testing of impedancemetric NO x sensors

Prototype solid-state electrochemical sensors using a dense gold sensing electrode, porous yttria-stabilized zirconia (YSZ) electrolyte, and a platinum counter electrode (Au/YSZ/Pt) were evaluated for measuring NO x (NO and NO 2) in diesel exhaust. Both electrodes were exposed to the test gas (i.e., there was no reference gas for the counter electrode). An impedancemetric method was used for NO x measurements, where the phase angle was used as the response signal. A portion of the tailpipe exhaust from the dynamometer test stand was extracted and fed into a furnace containing the experimental sensor. The prototype sensor was tested along with a commercially available NO x sensor. Simultaneous measurements for NO x , O 2, CO 2, H 2O, CO, and CH 4 in a separate feed stream were made using Fourier transform infrared (FTIR) spectroscopy and an oxygen paramagnetic analyzer. The experimental sensor showed very good measurement capability for NO in the range of 25–250 ppm, with a response paralleling that of the FTIR and commercial sensor. The prototype sensor showed better sensitivity to NO x at the lower concentration ranges. O 2 is an interferent for the experimental sensor, resulting in decreased sensitivity for measurement of NO x . Methods to overcome this interference are discussed.

Uncertainty evaluation of the 20 kN m deadweight torque standard machine

A deadweight-type torque standard machine of 20 kN m rated capacity (20 kN m-DWTSM) has been designed and developed by the National Metrology Institute of Japan (NMIJ) at the National Institute of Advanced Industrial Science and Technology (AIST). Each uncertainty contribution comes mainly from the performance of each mechanical part of the 20 kN m-DWTSM. Authors evaluated the uncertainty of the mass of the linkage weights, local acceleration of gravity, influence of air buoyancy on deadweight loading, initial moment-arm length (including CMM measurement and temperature compensation), and sensitivity of the fulcrum. This report deals especially with evaluation of the remaining contributions, namely the influence of arm flexure and reference line variation at the end of the moment-arm on best measurement capability (BMC). Estimation of BMC in the 20 kN m-DWTSM gave a relative expanded uncertainty of less than 7.0 · 10 −5 ( k = 2) for the calibration range from 200 N m to 20 kN m.

An Uncertainty of Laser Doppler Velocimeter Calibration for Air Speed Standard

A LDV calibrator used as the national standard of air speed was improved and the measurement uncertainty was estimated quantitatively in detail. A LDV is suitable for a transfer standard of air speed derived from lergth and time, but there are few examples of uncertainty analysis required for establishment of traceability. Thus, former LDV calibrator was developed to generate various velocities with a fine wire simulating a particle suspended in fluid flow. In this report, improvements were performed on the calibrator mechanisms, system configurations, measurement procedures and evaluation method. With these efforts, the best measurement capability (BMC) of calibration from 0.063% to 0.50% was achieved at the wire speed from 1.3 m/s to 40 m/s for backscatter LDV without reflector optics. The LDV under test showed remarkable velocity dependency at every filter range in the actual calibration result.