Digital interfacing

McConnell, M., Canales, M., and Lawler, G., A validation protocol for analog-to-digital interfaces in chromatographic data systems, LC-GC, 9, 486, 1991. 

The A/D board can reside either in the detector, an interface box, or in the computer. If the board is in the computer, it will have analog input terminals similar to a strip chart recorder or it will be connected to an interface box that will have this type of connector. If the A/D card is in the detector, the detector will have some type of digital interface port and a cable to connect it to the computer. In the personal computer world, once the signal is digitized outside the computer, it will be sent to the computer over one of three types of communication cables parallel, serial, or GPIB. 

Figure 4.5. Block diagram of pressure-jump relaxation apparatus with digitizing interface. [From Krizan and Strehlow (1974), with permission.]...

Krizan and Strehlow (1974) described a relatively simple digitizing interface for use in p-jump relaxation experiments which improves the accuracy and rapidity of data acquisition. A block diagram of the p-jump apparatus with digitizing interface is shown in Fig. 4.5. With this interface, one can sample by repeating the experiments and adding data to a small on-line computer. 

IEEE Standard Digital Interface for Programmable Instrumentation IEEE Std. 488-1975. New York IEEE 1975... 

In addition to producing sound, sound cards have another capability that is often overlooked. The Musical Instrument Digital Interface (MIDI—usually pronounced middy ) technology incorporated into most sound cards allows PCs to talk with (and in some cases, control) musical devices. With the addition of a special adapter cable that plugs into the game port on most sound cards, a PC can use external sound modules to produce sounds. MIDI technologies are used by most electronic keyboard players and professional musicians. However, you don t need to have an electronic keyboard or external sound module to play MIDI sounds. Most sound cards include a set of ICs that incorporate some of the sound-generating circuitry found in most electronic keyboards. 

IEEE-1394 A high-speed digital interface most commonly used to transfer data between computers and digital video cameras. It has a maximum data transfer... 

Fortunately, digital techniques are available commercially (see later discussion on commercial p-jump units), Krizan and von Strehlow (1974) developed one digitizing interface that can be used in p-jump analysis. 

An alternative to the TAC and PHA/ADC is the time-to-digital converter (TDC), a unit that combines the functions of the TAC and PHA/ADC. There are start and stop inputs and an output that provides a binary number directly proportional to the time difference between the stop and start signals. The TAC can be directly connected to a MCA or PC with the appropriate digital interface. 

IEEE Standard Modular Instrumentation and Digital Interface (CAMAQ, lEEE-Std. 583 Institute of Electrical and Electronic Engineers, New York, 1975. 

Digital interface some potentiostats feature auxiliary A/D inputs and D/A outputs that can be controlled by the software. These are convenient for controlling auxiliary equipment, such as electromechanical shutters or magnetic stirrers. GPIB used to be the standard interface to the computer for instmment control and data exchange. However, this >30-year-old standard is now outdated and is superseded by USB and/or Ethernet interfaces. The same goes for the even older - and much slower - RS-232 interface. 

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