High-speed Data Acquisition Board Research Articles

Particular Transient Regimes of Asynchronous Motors Supplied by PWM Converters

This paper presents a few aspects regarding the analysis of some dynamic regimes of asynchronous motors supplied at variable frequency. In this purpose, in the first part of the paper, there are detailed the Simulink blocks of a program for simulating the operation of driving systems with static converters with precomputed commutation moments. Then there are presented the simulations obtained with the help of this program in case when the supply frequency is modified by jump. The accent is laid on the rate of time-dependent variation of the stator current. The results obtained are compared with the experimental results obtained with the help of a high-speed data acquisition board. The paper ends with conclusions and references.

Study on The Measurement of Corrosion Product Concentration in The Feed Water System of A Power Plant

(Received August 8, 2011; Revised August 29, 2011; Accepted August 29, 2011)The iron oxide particles could be resulted from the corrosion of the circulating water system of a power plant.Because it may be one of the trouble materials which affect the power generation efficiency due to the depositionon steam generator tube and turbine blade, the continuous observation of its concentration is very important.The laser induced break-down detection (LIBD) technology was applied to monitor continuously the concentrationof corrosion products with the detection limit of ppb level. The measurement system consists of a Nd:YAG pulsed laser, a polarizing beam splitter, a flow-type sample cell, an acoustic emission sensor, a high speed data acquisition board, a personal computer, etc.. The performance test results confirmed that this technology can be effective to monitor the corrosion product concentration of the circulating water system of a power plant.

Measuring Droplet Impact Energy with Piezoelectric Film

A system for measuring water droplet impact energy is described, which consists of piezoelectric film connected to a high-speed data acquisition board in a personal computer. The system converts the impact forces of individual water droplets falling onto the piezoelectric film into an output voltage, which is measured and analyzed. Eight DT3-type piezoelectric films were calibrated under laboratory conditions for kinetic energy values ranging from 0.01 × 10−3 to 1.2 × 10−3 J by releasing water droplets of various sizes from specific heights. The DT3-type piezoelectric film is effective for water droplets smaller than 4.6 mm in diameter. Results were used to produce a general model for the response of this film type. The ease of use and robustness of the system was demonstrated by measuring droplet impact forces under a lateral-move irrigation machine.

Implementation of a networked virtual nuclear magnetic resonance spectrometer

Virtual instrumentation offers several advantages over traditional instruments, such as the ability to simplify hardware design, the flexibility to easily change device function, and more recently,the ability to operate instrumentation from remote locations. In this article, a nuclear magnetic resonance (NMR) receiver is being developed using virtual instrumentation technology. In lieu of the analog technology used in traditional NMR instruments, a high-speed data acquisition board is used to directly digitize the radio-frequency (RF) NMR signal. This signal is then demodulated and processed from within LabVIEW®. Work is also being done so that the instrument can be operated over the Internet in a client–server mode. The resulting receiver was tested using both hardware- and software-simulated NMR signals. © 1998 National Instruments. Published by John Wiley & Sons, Inc. Lab Robotics and Automation 10: 115–118, 1998

Heat transfer to nonmiscible liquid-liquid mixtures flowing in a vertical tube

Phase distribution and heat transfer measurements were carried out in an n-heptane-water mixture flowing upward in a vertical stainless steel tube of 16-mm inner diameter. For the phase distribution measurement a very high frequency impedance probe was used with a tip diameter of 0.58 mm. The volumetric phase fraction of n-heptane was varied between 0 and 1, the mixture velocities between 0.5 and 2.3 m/s, and the temperature between 30 and 80°C. By means of a high-speed data acquisition board implemented in a personal computer, two methods for signal conditioning were tested: level thresholding and derivative thresholding. Derivative thresholding proved to be advantageous because it is insensitive to baseline drift and allows detection of droplets of the discontinuous phase. Heat transfer to the liquid-liquid mixture depends on the phase distribution in the boundary layer at the wall. It was found that the change from water-dominated heat transfer to n-heptane-dominated heat transfer occurs nearly abruptly at n-heptane volumetric phase fractions between 0.6 and 0.7. An estimate of the heat transfer coefficient as a function of the mean volumetric fraction ϵ by a linear interpolation between the heat transfer coefficients at ϵ ns = 0 and ϵ ns = 1 would therefore lead to significant errors. The few correlations available in the literature are also not suitable to predict heat transfer to water- n-heptane mixtures. Therefore a preliminary prediction method is proposed based on the experimental data for phase distribution near the heated wall.