Transient data acquisition system

The problem is much more acute, however, for digitizing FID s of solid samples (without artificial, or other kinds of, narrowing) and the reason is two fold. First, fast ADC s are very much harder to make than slower ones. At the time of writing, there are new commercial modular units which convert analog signals into 8-bit digital words at 10 MHz at moderate (but not cheap) cost and the field is rapidly advancing. 

MHz whereas the actual FID is made up of 2K (2048) 8-bit words at 6 MHz. This scheme can be extended to higher rates in an obvious way. 

There are now commercial digitizers which work well in excess of 20 MHz at 8-bits. It is no longer worthwhile even thinking about designing your own digitizer for this reason. 

The second reason is that a high digitizing rate permits you to move the Nyquist frequency sufficiently far away from the spectral features. If you make the Nyquist frequency just barely larger than the frequency range of interest and put in a low pass filter to coincide with the Nyquist frequency, two problems develop because the filter is not ideal. First, there is noise folded back into the spectrum from that part of 

An external trigger capability for the digitizer is useful for at least two reasons. One is to be able to sample the magnetization at the correct points in a multiple pulse experiment. (An example would be to sample just the tops of the echoes in a CPMG experiment as described in I.C.2.) The other reason is to allow for synchronization of two digitizers, for example, in quadrature detection. 

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For some mass spectrometers, such as TOF mass spectrometers, for reasons of data transfer speed and data storage capacity, the data acquisition system needs to accumulate data for a period of time in the summing memory, and forward the accumulated data to the data system. Each spectrum is added to the sum of the previous spectra so that a continuous summation process takes place. This type of data acquisition system is called digital signal averaging (DSA) or integrating transient recorder (ITR). Figure 3.8 illustrates the principle of mass spectrum acquisition with this type of system. 

The transient hot-wire method can be used to measure the thermal conductivity of nanofluids in this study. As schematically shown in Fig. 4, the transient hot-wire measurement system contains a DC power supply, the Wheatstone bridge, a data acquisition system, a nanofluid container, and a computer system to analyze the... 

Since the technique was first employed in 1931 (Stahlane and Pyk, 1931) to measure the thermal conductivity of powders, there have been significant improvements in the practical realization of the technique. In modem instm-ments the wire sensor aets both as the heat source and as a thermometer. Rapid development of analogue and digital equipment as well as of eomputer-driven data-acquisition systems, have meant that precise measurements of transient electrical signals can be made quickly. Thus, it has become possible to measure the resistance change taking place in the hot wire as a consequence of its temperature rise with a... 

Fuel cell circuit for current interrupt test consisting of load, on/off switch, and a transient recording device such as oscilloscope of data acquisition system (DAS). 

The basic components include a Nd YAG pulsed laser system which is coaxial with a He Ne pilot laser and visible light optical system. The latter system enables the analytical area of interest to be located. The TOF-MS has a flight path of 2m in length, with an ion detection system that includes an electron multiplier detector, a multichannel transient recorder, together with a computer acquisition and data processing system. 

The direct characterization of an eT mechanism requires a much more complicated technique time-resolved spectroscopy. The solution containing the system under investigation is irradiated by a laser pulse, and the absorption spectra of the solution are consecutively recorded at chosen and very short time intervals (e.g. every 10 ns). If, in the envisaged two-component system F1 M, an M-to-Fl eT process takes place upon illumination, one should be able to measure the absorption spectra of Fl and M" ", as well as their decay, which allows the determination of the lifetime of the transient species F1 M. It goes without saying that very sophisticated and expensive instrumentation is required to carry out this type of experiment. Moreover, the smaller the fluorophore lifetime and the faster the back-electron transfer process, the more rapid and expensive the data acquisition equipment required. In particular, narrow laser pulses and especially fast data collections are needed for systems such as 1, where a short-living polyaromatic fluorophore (anthracene, r = 5 ns) is linked to the electron donor (or acceptor) group by a rather short carbon chain. 

Fig. 3. Block diagram of data acquisition and analysis system. In our laboratories two systems based on the above have been built. One is a Durrum-Gibson stopped-flow spectrophotometer coupled through a Datalab DL901 transient recorder to a Commadore PET 32K minicomputer (used for data in Fig. 2). Another system consists of a Canterbury SF-3A stopped-flow instrument interfaced, via a Datalab DL901 transient recorder to an Exidy Sorcerer minicomputer. Software is available.

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