Voltage Supply (voltage + supply)

Distribution by Scientific Domains

Selected Abstracts

Pump-free and low-cost negative pressure sampling device for rapid sample loading in MCE

Hongmei Hu
Abstract A pump-free and low-cost negative pressure sampling device for injecting well-defined non-biased sample plugs into the separation channel of MCE was developed. It was composed of a pipet bulb, a 3-way electromagnetic valve and a single voltage supply at constant voltage. A sub-atmospheric pressure was created by hand-pressing air out of the pipet bulb and retained in it by switching the 3-way electromagnetic valve at cutoff position. During the sample loading stage, the sub-atmospheric pressure in the pipet bulb was applied via a 3-way electromagnetic valve to the headspace of the sealed sample waste reservoir (SW). A pinched sample plug was formed at the channel intersection in less than 0.5,s. Once the 3-way electromagnetic valve was switched to connect SW to ambient atmosphere to release the vacuum in SW, electrophoresis separation was consequently activated under the electric potentials applied. Experimental results demonstrated the pump-free negative pressure sampling device worked well in a wide vacuum degree ranged from ,250 to ,30,mbar with a satisfactory analytical precision. The sample consumption for each cycle was calculated to be 51,12,nL under the sampling pressure. Theoretical deduction indicates that the volume of the pipet bulb can be further reduced to 1,mL, which is critical for minimizing the sampling device for MCE. [source]

Independent control of positive- and negative-sequence current components in a doubly fed machine

J. Bendl
Abstract This paper analyses the operation of a power unit with a doubly fed machine. A novel vector control method is presented which enables independent control of both positive- and negative-sequence components of stator currents. Also, operation of the system under the condition of unbalanced voltage supply applied to the stator is discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A switched-capacitor programmable gain amplifier using dynamic element matching

Jun Wang Non-member
Abstract This paper discusses the effect of capacitor mismatch errors on gain accuracy of switched-capacitor programmable gain amplifier (SC PGA). To improve gain deviations caused by mismatch errors, the dynamic element matching (DEM) algorithm is applied to the SC PGA circuits. It uses digital gain-control signal to dynamically vary the matched capacitor combinations so that the effective capacitances of the sampling and feedback capacitor arrays are averaged, and thus the gain deviations due to capacitor mismatch errors are eliminated to a significant extent. The distortion caused by mismatch errors shift to certain frequency bands, and could be reduced or removed by subsequent processing such as lowpass filtering. A 4-bit SC PGA using DEM was designed in 0.25 µm CMOS process with 2.5 V voltage supply, including offset cancellation and clock bootstrapped circuits operating at a sampling frequency of 10 MHz. Test results have indicated that gain deviations due to mismatch errors are substantially reduced. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Amplitude estimation for near-sinusoidal oscillators by using a modified Barkhausen criterion

H. Jardón-Aguilar
Abstract By using an approach based on the Taylor/Volterra series, nonlinear amplifier characteristics can be introduced into the Barkhausen criterion in order to estimate the amplitude for near-sinusoidal oscillators. The characteristic equation is similar to the 1st -order determining equation obtained by Chua. This new method includes all desirable features of Chua's equation and lets us generalize the linear approach directly to a nonlinear one without losing the mathematical simplicity of the Barkhausen criterion. It also allows us to determine the oscillation amplitude with a desired accuracy. Moreover, this method investigates the influence of the feedback factor and the voltage supply on the oscillation amplitude. Employing only the 3rd -order nonlinearity of the amplifying element, the amplitude of the oscillation predicted by the modified Barkhausen criterion was compared to the one estimated using the transient analysis of SPICE, the harmonic balance analysis of Serenade, and by measurements. The amplitudes obtained by these four approaches for several feedback factors and supply voltages are in good agreement. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]