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Metering
Published in Anthony J. Pansini, Electrical Distribution Engineering, 2020
Basic electric meters include the ammeter for measuring current in amperes, the voltmeter for measuring electrical pressure in volts, and the wattmeter for measuring power in watts. The ammeter operates on the interaction of a magnetic field, set up by the current to be measured, with the field of a permanent magnet. The voltmeter is essentially an ammeter connected in series with a fixed resistance. A wattmeter is a combination of both the ammeter and voltmeter elements.
Unravelling Uncertainty Through Simple Examples
Published in K. Sundareswaran, A Leaner’s Guide to Fuzzy Logic Systems, 2019
In the field of measurement, precision and accuracy are used interchangeably, as the two are related concepts. However, there is a fundamental difference between the two. Precision refers to a number of digits/decimals representing the measurement and depends on the granularity of the scale, i.e. the finest division restricts the precision. Thus, a measured current of 3.1098 A is more precise than 3.1 A. On the other hand, accuracy measures the degree to which a measured value coincides with the “true” or “actual” value of a variable. Accuracy is the difference between a measured result and the true value. If the actual power consumed by an incandescent lamp is 100 W and if a wattmeter measures 101.8 W, the accuracy of the instrument is −1.8 W. Thus, the accuracy of an instrument is affected by external and internal influences, and precision is affected only by a number of divisions on the scale.
W
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
Watt, James (1736-1819) Born: Greenock, Scotland Best known for his work in the development of efficient steam power. Watt began his career as an instrument maker. When asked to fix a troublesome Newcomen engine, he began to make improvements. Watt eventually partnered with industrialist Matthew Boulton to form a steam engine company. Watt is credited with having devised the horsepower system. The unit of power, the watt, is named in his honor. watt-VAR meter meter capable of simultaneously measuring the real and reactive power delivered to an AC load. wattmeter an instrument for measuring electric power in watts. A wattmeter requires connections to measure both the current through and the voltage across the load being measured. wave equation equation governing the evolution of a wave; in electromagnetics any of several equations or equation sets starting from the most general, nonlinear multivariable differential Maxwell-Heaviside equations and ranging down to the simplest first-order rate equations. wave impedance the ratio of the transverse electric and magnetic fields inside a waveguide. wave optics formalism for optics in which the fields are represented as wave phenomena, in contrast to other ray or particle optics models. wave plate transparent anisotropic medium that introduces polarization-dependent phase shifts on an optical wave.
The Effect of Square Tube Location in a Vertical Array of Square Tubes on Natural Convection Heat Transfer
Published in Heat Transfer Engineering, 2018
Mohamed Ali, Abdullah Nuhait, Redhwan Almuzaiqer
The experimental uncertainty is estimated in the calculated results on the basis of uncertainties in the primary measurements. It should be noted that, some of the experiments had to be repeated in order to check the calculated results and the general trends of the data to be sure that the experiment is going as planned. The error in measuring the temperature, estimating the emissivity and in calculating the surface area is ± 0.5 °C, ± 0.02, and ± 0.003 m2, respectively. The accuracy in measuring the voltage is taken from the manual of the Wattmeter as 0.5% of reading ± 2 counts with a resolution of 0.1 V and the corresponding one for the current is 0.7% of reading ± 5 counts + 1 mA with a resolution of 1 mA. At each heat flux, 40 scans of the temperature measurement were made by the data acquisition system for each channel and the mathematical averaged of those scans was obtained. It should be noted that the uncertainty in the calculated result was estimated using the method recommended by Kline and McClintock [24] and Moffat [25] and a computer program was written to do that. Table 1 shows the maximum itemized uncertainties of the calculated result.
Operation Characteristics of a High Temperature Special Shaped Heat Pipe Used in Solar Thermochemical Reactors
Published in Heat Transfer Engineering, 2019
Tingting Ma, Xiaoyuan Wang, Yuezhao Zhu, Yang Li
A special-made electric furnace was used to heat HTSSHP, and its power output was controlled by a voltage regulator (TDGC2J-5, CCLair, China) along with a wattmeter (tm9, TECMEN, China) with a maximum output power of 1,400 W. The heat coil was spirally arranged at the electric furnace top, which was interposed into the absorber chamber of HTSSHP in tests. To minimize the heat loss to ambient and accelerate the startup process, HTSSHP was completely insulated by aluminium silicate felts. The thickness of the thermal insulation near cooling side was just 90 mm versus 180 mm at the adiabatic section and furnace bottom. The whole setup was fixed at a metal support, by which the inclination angles (±90°, vertical orientation is defined as 0°) can be adjusted.
Experimental comparison of Triton X-100 and sodium dodecyl benzene sulfonate surfactants on thermal performance of TiO2–deionized water nanofluid in a thermosiphon
Published in Experimental Heat Transfer, 2018
Adnan Sözen, Metin Gürü, Tayfun Menlik, Uğur Karakaya, Erdem Çiftçi
The schematic view of the experimental set-up is given in Figure 4. The photograph of the experimental set-up is also represented in Figure 5. A straight copper tube with an inner diameter of 13 mm, an outer diameter of 15 mm, and a length of 1 m, 400 mm of which was the evaporator whereas 200 mm was the adiabatic section and the remaining 400 mm was the condenser, was used as the heat pipe in the present study. The evaporator region was heated by an electrical heater with a nominal power of 1,500 W comprising of a Ni–Cr wire. The heater was fully insulated by glass wool to hinder the heat leakages. The input power was experimentally measured and monitored through a wattmeter in watt unit (Fluke-43b analyzer).