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Methods of generation of shock waves and measurement of gas-dynamic parameters in dynamic experiments
Published in G. I. Kanel′, Shock Waves in Solid State Physics, 2019
The main method of recording mechanical stress or pressure is currently the method of manganin gauges. The use of manganin gauges is based on the high sensitivity of the resistivity of manganin to pressure, and on low sensitivity to temperature changes. Usually, the gauge is made in the form of a flat zigzag tape with a thickness of 10–30 µm, occupying an area of ~0.1–1 cm2. The sample is made multipart; the gauge is laid between the sample plates and, if necessary, is separated from them by insulating films (Fig. 2.20). During the measurements, a current is passed through the gauge, a voltage drop across it is recorded with an oscilloscope, which increases with increasing pressure acting on the gauge. To improve the signal-to-electrical noise ratio and eliminate gauge overheating, pulsed current sources of 5–10 A and duration of ~100 μs are used. The gauge is included in the resistance bridge or other differential registration schemes are used in order to eliminate the constant component of the signal, determined by the initial resistance of the gauge, and thereby improve the measurement accuracy. The two-point scheme is used for relatively high-resistance (5–50 ohms) gauges. In some cases, it is advisable to use gauges with an initial resistance at the level of tenths or hundredths of Ohms. Such gauges have, in particular, the advantage that their readings are less sensitive to the shunting effect of the electrical conductivity of the environment. Low-resistance gauges are included in the measuring circuit in a four-point scheme.
Engineering materials and heat treatment
Published in Roger Timings, Fabrication and Welding Engineering, 2008
This is contained within the case of the indicating instrument. Its purpose is to improve the stability to the system. The resistance of electrical conductors increases as their temperature increases and the conductors that make up a pyrometer circuit are no exception. The variation in resistance with temperature would seriously affect the calibration of the instrument if the ballast resistor were not present. This resistor is made from manganin wire. Manganin is an alloy whose resistance is virtually unaffected by changes in temperature. By making the resistance of this ballast resistor very large compared with the resistance of the rest of the circuit, it swamps the effects of any changes in resistance that may occur in the rest of the circuit and renders them unimportant.
Engineering materials and heat treatment
Published in Roger Timings, Engineering Fundamentals, 2007
This is contained within the case of the indicating instrument. Its purpose is to give stability to the system. The resistance of electrical conductors increases as their temperature increases, and the conductors that make up a pyrometer circuit are no exception. The variation in resistance with temperature would seriously affect the calibration of the instrument if the ballast resistor were not present. This resistor is made from manganin wire. Manganin is an alloy whose resistance is virtually unaffected by heat. By making the resistance of the ballast resistor very large compared with the resistance of the rest of the circuit, it swamps the effects of any changes in resistance that may occur in the rest of the circuit and renders them unimportant.
Experimental and numerical investigation on cooling characteristics of Gifford-McMahon pulse tube cryocooler
Published in Experimental Heat Transfer, 2023
Debashis Panda, Ashok K Satapathy, Sunil K. Sarangi
Oil-filled pressure gauges are adopted to display the pressure at the high and low-pressure lines of the compressor. Endevco make 8510B-500 piezo-resistive pressure transducers are adopted at top of the regenerator, pulse tube, and in between orifice valve and buffer to measure the pulsating pressure. Input signal to the pressure transducers are provided from an Endevco differential voltage amplifier and an oscilloscope records the outputs. PT-100 Ω thin film type temperature sensors are adopted to measure the temperature in desired positions of the regenerator, cold heat exchanger, pulse tube, and warm heat exchanger. The applied heat load is measured with the help of a manganin wire. A more detailed description about the measuring instruments has been discussed in reference [19], and the detailed technical specifications of the measuring instruments are tabulated in Table 1.
Thermoeconomic performance optimization of an orifice pulse tube refrigerator
Published in Science and Technology for the Built Environment, 2020
Debashis Panda, Ashok K. Satapathy, Sunil K. Sarangi
The cooling capacity is measured with the help of a manganin wire by winding it over the cold heat exchanger of the OPTR. The total uncertainty in cooling capacity measurement is the sum of total uncertainty due to the resistance of the manganin wire, current/voltage measurement. It is assumed here the uncertainty associated with measuring instruments follows a rectangular distribution (k = 2 and a confidence level of 95%). The resistance of the wire is measured by conducting 10 different observations by flowing current. The type A uncertainty of the wire has been calculated by measuring the resistance values at 10 different observations. The associated type B uncertainty is small and thus neglected for this measurement. The total resistance value is found to be 30.01 ± 0.027 Ω. Uncertainty associated with current source is 1%. The voltage measurement follows a rectangular distribution with 95% of confidence level. The uncertainty in cooling power measurement is the combination of individual uncertainty (i.e., resistance and current/voltage) in product form and its net uncertainty is calculated according to reference (Holman 2012). It is observed that the total uncertainty falls between 2% - 3% below 30 W of refrigeration capacity. Above 30 W the uncertainty value rises up to 3.5%.
New EHL Modeling Data for the Reference Liquids Squalane and Squalane Plus Polyisoprene
Published in Tribology Transactions, 2018
Scott S. Bair, Ove Andersson, Farrukh S. Qureshi, Michele M. Schirru
The viscometer is an improved version of the instrument described in Bair (40). The intensifier pressure relation is now determined by the resistance of a manganin wire that was calibrated with a dead-weight tester to 1.4 GPa. The hollow sinker was fabricated with an iridium core. The large mass density of iridium reduces the error in the buoyancy correction resulting from error in the sample density estimate. Density was estimated from the Tait equation (Bair (21)). Measurements were made at 21.5 and 40°C. It was not possible to repeat the previous results at 20°C because of the high laboratory ambient temperature of an Atlanta summer. The new measurements are reported in Table 2. Because of the rather long fall times, lasting up to 4 h, the estimated uncertainty in viscosity is 12% here. Uncertainties for pressure and temperature are 5 MPa and 0.3°C, respectively.