Digital to analogue converter

The sample frequency of the ADC (analogue to digital converter) should be 8 times higher than the test frequency (centre frequency of the spectrum). In dependence of the application, different ADC- boards are used. A standard board (20520) provides 8 bit resolution and up to 100 Msamples/s in single shot mode. For manual tests, up to 400 Msamples/s can be reached in the repetition mode. For scanning systems with high frequencies boards up to 400 Msamples/s (single shot) are available. 

In order to test a wide range of materials a series of ultrasonic pulser/receiver boards has been developed. In combination with an ADC-board (analogue-to-digital converter) a PC can be converted to a high performance ultrasonic system not only for manual testing but also for automatic testing and imaging systems. 

C = transmitter D = signal transmission E = analogue-to-digital converter(A/D) F = digital-to-analogue converter (D/A) ... 

A second factor that can influence quantitation is digital resolution in the intensity direction (or vertical scale in the graph). This is due to the analogue to digital converter (ADC) and sometimes can be experimentally corrected by changing the receiver gain. However, for most modern instrumentation this limitation is not so serious and, therefore, will not be discussed in detail below, but is illustrated in Problem 3.7. 

The interface receives, conditions and digitizes the analogue signals (those given by a beam, an ionic current, temperatures, voltages) output by the mass spectrometer and sends them to the computer. It acts an analogue-to-digital converter (ADC). 

Finally, the analogue-to-digital converter should have a resolving power which is large enough (see Griffiths and de Haset, 1986) with respect to the intensity steps (Fig. 3.3-13e and f)-... 

A multichannel analyzer (MCA) with a minimum of 4096 channels should be connected to a keyboard and display screen for input and output of data and interaction with a computer. Several kits are available for the conversion of personal computers (PCs) into MCAs. Basically there are three types of conversion kits. One makes use of board with an analogue-to-digital converter (ADC) that simply clips into the PC a second type uses a clip-in board with an external ADC and the third type uses a multichannel buffer (MCB) connected to the PC. All of these PC-based MCA systems are relatively inexpensive and are very suitable for use in germanium and sodium iodide y-ray spectrometry. 

Frasinski et al. [15] devised a triple coincidence technique to study double ionization in the single photon regime. In these photoelectron-photoion-photoion coincidence experiments, the photoelectron provides the start pulse to an analogue-to-digital converter and the two ions the stop pulses and it was an easy matter to ensure that there was less than one molecular ion in the interaction region for the period of measurement of the ion energies, about 10 fis. In the multiphoton case, however, may ions are produced per laser pulse and this conventional approach cannot be employed. 

The signal (2.3.12) is in the audio-frequency regime, where it can be sampled via analogue-to-digital converters (ADCs) and stored in a computer for further processing and display. Generally, the response is acquired at equidistant sampling intervals At. The... 

Fig. 1, H NMR spectra of a lysozyme solution (10 mM in 10 90 H20 H20, pH 3.7) (A) without water suppression and (B) with the water resonance suppressed using the Water-PRESS sequence (see p. 305). Both spectra were acquired at 310 K at 300 MHz and in both cases a 7t/2 observe pulse was used. To avoid saturation of the analogue-to-digital converter the receiver gain used in acquiring spectrum (A) was 28 dB less than that used in acquiring spectrum (B). (From Price et a/. )...

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