Digital devices

The foregoing demonstrates that modern digital devices offer highly reliable, state-of-die-art microprocessor technology that controls turbomachinery strings, monitors operating data, stores data for subsequent evaluation, communicates to odier systems, and can expand with future technologies. 

An inherently safer control system design will, where possible, include options for on-line reliability tests and inspections. Within digital devices, this is done using watch-dog timers to assure the signals are processed. 

RAC publications include data summaries for specific component types, such as hybrid microcircuits, small, medium and large-scale integration digital devices, linear and interface devices, digital monolithic devices, and discrete semiconductors. In addition, there are reliability and equipment maintenance data books that provide the failure and repair time data on military electronic equipment by application such as subsystem. 

With the advent of digital relays, the situation changed dramatically. Not only could the relays record the fault current and voltage and calculate the fault location, they could also report this information to a central location for analysis. Some digital devices are used exclusively as fault recorders. 

There are three basic types of controllers that are commonly used for continuous feedback control. The details of construction of the analog devices and the programming of the digital devices vary from one manufacturer to the next, but their basic functions are essentially the same. 

Molecular photoionic devices with switchable response, at the ensemble level, display nonlinear in/out characteristics which can be operated either as analogue or digital devices by proper control of the ion concentration input variable. When... 

In PSpice both a 7414 and a CD4093 were used. The 7414 is the digital model for the Schmitt trigger inverter. To use the digital device for an analog measurement, E sources (voltage-controlled voltage sources) were used as buffers. The schematic used for the PSpice model is shown in Fig. 8.59. The results are displayed in Fig. 8.60. 

Up to now, we have given a general theoretical development of the self-beat technique. As a practical illustration of the experimental apparatus used to detect autocorrelation functions in scattering experiments, the equipment currently used in our laboratory will now be described. While our treatment of the autocorrelation function has been in terms of an analog signal, the computer that measures this function is actually a digital device. This is based on the fact that it is also valid to count the scattered photons in order to calculate Ci(r) as the optical intensity signal is essentially determined by the number of photons that strike the photocathode per unit time. We have then... 

The electrochemical timer is a device that can be set to switch a circuit on or off at a given time. It was of great practical importance until the development of microelectronic digital devices, since it could be set to operate for periods of minutes to months, with an accuracy of better than 1%. We describe it here to show how an understanding of the fundamental electrochemical processes taking place can lead to the development of a simple and very useful device. 

Digital devices such as computers work with sharply defined logical elements—bits which take the values of 1 (true) and 0 (false) i.e., their work is based on classical prepositional logic or its mathematical equivalent, Boolean algebra. The fuzzy nature of human reasoning, on the other hand, makes things much more flexible, but may lead to irreproducible results and hence be a source of error. For instance, two chemists may draw different conclusions about a structure derived from the same spectral information from the same unknown compound measured on the same instrument. In contrast, the classical logic of computers always leads to the... 

Freeze-dryer controls have experienced the most dramatic developments in recent years. The original mercury gauge and thermostatically controlled heaters were initially replaced with analogue vacuum gauges, thermocouples and controls. Eventually, the latter two were superseded by digital devices. 

In addition to the linear devices, accelerated moisture tests under identical conditions were also performed on the digital devices on A-42 leadframes. The results are given in Table VI. 

Table VI. Failures Upon Accelerated Life Testing of Devices Encapsulated with GE s Developmental Molding Compound. Digital Devices on A-42 Leadframes...

Define direct digital and supervisory control. Which one is used for regulatory control actions and which for servo operations In a supervisory control mode, what are better as local controllers, analog or digital devices Discuss relative advantages and disadvantages. 

A/D converter (analog to digital)—Device which converts analog signals from process sensors into digital form for use by computers and other digital equipment. 

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