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Ground movements and monitoring
Published in David Chapman, Nicole Metje, Alfred Stärk, Introduction to Tunnel Construction, 2017
David Chapman, Nicole Metje, Alfred Stärk
It is important to understand the quality of the data received from instrumentation. For this reason, some important definitions related to monitoring and instrumentation are given below (after Dunnicliff and Green 1993): Conformance: the presence of the measuring instrument should not alter the value of the parameter being measured. The degree by which the parameter is altered by the instrument is known as its conformance.Accuracy: this is the closeness of a measurement to the true value of the quantity measured. Accuracy is synonymous with degree of correctness. The accuracy of an instrument is evaluated during calibration to a known standard value. It is customary to express accuracy as a ±number.Precision: this is the closeness of each of a number of similar measurements to the arithmetic mean. Precision is synonymous with reproducibility and repeatability. The number of significant figures associated with the measurement indicates precision. For example, ±1.00 indicates a higher precision than ±1.0.
Instrumentation in Asphalt and Concrete Pavement
Published in Rajib B. Mallick, Tahar El-Korchi, Pavement Engineering, 2017
Rajib B. Mallick, Tahar El-Korchi
Data are obtained from in-place instruments through the use of appropriate data acquisition systems. Such data acquisitions systems are controlled by a suitable software (such as LAB VIEW) through a computer system, and include appropriate modules or devices to interface between the instruments and the computer. In many cases, data loggers are used to collect and store data, which are then periodically transferred to a computer by using a suitable software and connection cable. As required the software can be used to trigger data acquisition on the basis of some other signal, such as data coming from a weigh-in-motion (WIM) signal (as a truck passes by the instrumented section). The relevant information about the instruments (such as gage factor or calibration constant) is input into the software, which then makes all the relevant computations on the basis of the acquired data and stores the data in ASCII or spreadsheet format or even displays data in graphical format. Various types of hardware and software are available—an example is shown in Figure 24.8.
Measuring and marking out
Published in Roger Timings, Fabrication and Welding Engineering, 2008
No matter how accurately measuring equipment is made, and no matter how sensitive it is, one of the most important factors affecting the accuracy of measurement is the skill of the user. The more important procedures for the correct use of measuring equipment can be summarized as follows. The measurement must be made at right angles to the surface of the component.The use of a constant measuring pressure is essential. This is provided automatically with micrometer callipers by means of their ratchet. With other instruments such as plain callipers and vernier callipers the measuring pressure depends upon the skill and ‘feel’ of the user. Such skill only comes with practice and experience.The component must be supported so that it does not distort under the measuring pressure or under its own weight.Measuring instruments must be handled with care so that they are not damaged or strained. They must be cleaned and kept in their cases when not in use. Measuring instruments must be regularly checked to ensure that they have not lost their initial accuracy. If an error is detected the instrument must be taken out of service immediately so that the error can be corrected. If correction is not possible the instrument must be immediately discarded.
Performance evaluation of multiple particulate matter monitoring instruments under higher temperatures and relative humidity in Southeast Asia and design of an affordable monitoring instrument (ManPMS)
Published in Instrumentation Science & Technology, 2023
Nam Duong Thanh, Hoa Tran Thi, Trung Nguyen Quang, Huy Nguyen Van, Giang Hoang Nguyen, Quyet Nguyen Huu, Tung Tran Son
Besides ambient temperature, relative humidity also affects the accuracy of an instrument. Its impact on the instruments was analyzed by dividing the humidity range into 4 equal intervals and calculating the relative bias of each interval. Only TEOM showed that relative humidity had a significant effect on the relative bias when compared against both reference instruments. In particular, as the humidity increased, the relative bias level decreased, rather than increased as shown in previously.[42,43] Even though higher humidity would cause the PM to hygroscopically grow, the relative humidity remained constantly high for the duration of the experiment and usually fluctuated 10% between noon and midnight. Thus, it may be the continuous high level of humidity that contribute to the stability of TEOM. The same trend was also observed in Airborne despite relative humidity not having a significant effect on the relative bias level. Moreover, Airborne should, theoretically, be more prone to hygroscopic growth. Recent studies have shown that at high relative humidity, its effect on hygroscopic growth was either a plateau or insignificant (Figure 9).[44,45]
Optimization design for reducing the axial force of a vaned mixed-flow pump
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Di Zhu, Ruofu Xiao, Zhifeng Yao, Wei Yang, Weichao Liu
The experiment is conducted using the hydraulic test rig for pumps. Figure 13 is the test rig schematic. Figure 14 shows the pump model installed on this test rig. Hydraulic performance is calculated by measuring pressure, flow rate, and shaft power. The pressure is measured by a pressure transducer and the accuracy is within ± 0.05%. The flow rate is measured by an electromagnetic flow meter and the accuracy is within ± 0.18%. The shaft power is measured by a power meter and the accuracy is within ± 0.10%. The uncertainty of two or more measured data can be calculated by a synthetization equation (Bo & Chen, 2004). The high accuracy of the instrument ensures the accuracy of the experiment. The pump head can be calculated by: where pout is the outlet pressure and pin is the inlet pressure. The pump efficiency can be calculated by: where Q is the inlet flow rate and M is the torque on shaft.
Effective density of airborne particles in a railway tunnel from field measurements of mobility and aerodynamic size distributions
Published in Aerosol Science and Technology, 2018
In addition to the effect of chemical composition and particle shapes related to the origin of the particles on their density, the effective density value may differ if determined with different algorithms or different detection systems (DeCarlo et al. 2004). It hence can be used in return to calibrate mass concentrations of particles measured with number-based instruments to obtain comparable levels of the results measured simultaneously with gravimetrical methods. Commonly used instruments for field measurements use aerodynamic, mobility, optical, and gravimetric techniques. Although optical measurement were not included in our study, further studies on effective density involving the calibration or comparison of optical size measurements to aerodynamic and mobility diameter measurements would be interesting. In this study, parallel measurements were performed with aerodynamic, mobility, and gravimetrical instruments. When it came to aerodynamic size distributions and gravitational mass concentrations, similar hourly variations in the effective density were estimated using the measurements with the TEOM-ELPI and the TEOM-APS + SMPS, except that the former shows a lower level than the latter (Figure 5). For the comparison between aerodynamic and mobility diameter detection techniques, the fitting of the FMPS to the ELPI gives a slightly higher value of effective density than that produced by the comparison between SMPS and ELPI. To better interpret those results, it would be beneficial to consider the performance of the different instruments.