Output devices

In safety applications on machinery, the most common output reaction to a safety-related input such as an interlocked guard being opened or the emergency stop button being pushed, is for power to be removed and/or for brakes to be applied and for them to remain appUed until a reset signal is provided. In electrical-only systems, the reaction is to have power disconnected to remove the risk of electrical injury. 

Output devices used to implement safety functions must be adequately rated for their duty and have an appropriate level of reliability and fault tolerance. They should also be designed so that, wherever possible, faults are revealed and do not lead to the loss of the safety function for example, electromechanical brakes should be designed to be held-off by being energised so that a loss of supply fault will lead to the brake being applied. Braking systems can be quite complex in practice, but their principles are quite straightforward. The main techniques are as follows. 

Mechanical brakes use friction linings to stop mechanical parts when the brake is applied. The brakes are normally held off under electrieal, pneumatic or hydraulic power and are spring-apphed. 

In this type of system the a.c. electric motor is first disconnected from its supply and a d.c. current injected into its windings for sufficiently long to stop the motor. The circuit diagram in Fig. 13. 25 shows the basic features of this type of system. Pressing the start button energises relay R and closes the direct-on-line starter contacts to supply three-phase power to the induction motor, which will then accelerate to its working speed. The starter is held on via contacts Rl. 

In capacitor braking, the motor is disconnected from the supply, then connected to a capacitor for a preset time and then short circuited during the final deceleration stage to stop the motor. 

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IDVl INPUT DEVICE ID IDV2 OUTPUT DEVICE ID... 

Many of the tasks once performed only ia a high ead electronic pagiaation system, often called color electronic prepress systems (CEPS), are possible by usiag persoaal computers and work stations. Pages are composed on screen, and the results are output typically as PostScript files. The data are transferred over a network to the final output device. 

The networking of personal computers has continued and has enabled the sharing of expensive hard-copy output devices and other peripherals and has provided the significant benefit of faciUtating the transfer of data between computers. Joint authorship of technical articles is a quick and easy process with networked computers. The interappHcation communication that today links appHcations within a single computer will transparentiy link appHcations on networked computers. Voice-annotated documents are already available. 

Control-System Components The three principal elements of a control system are the sensing device which measures the error as the deviation from the set point, means for transmission and amphfi-cation of the error signal, and the control output device in the form of a seivo-operated valve. In the case of the direct-acting flyball governor (Fig. 29-18) these three elements are combined in the flyball element and the linkage that connects to the valve. 

System hardware consists of the central processor, the input devices (usually a keyboard), the output devices (probably both a video display terminal and a hardcopy printer), long-term storage devices, and perhaps communications components. In smaller systems, more than one of these components may be built in to one unit, while in larger systems there may be many units each of several components associated with the system. 

The drawings were produced using the computers and substantial array of graphical output devices at the Center for Research in Computing Technology at Harvard University.5... 

Procedures and controls shall include use of authority checks to ensure that only authorized individuals can use the system, electronically sign a record, access the operation or computer system input or output device, alter a record, or perform the operation at hand. 

Access to computer system input or output device (Can input or output devices be altered without authority checks in a manner that will predictably affect results )... 

Quartz probes fitted with thermocouples to measure the temperature, and follow the movement of the sample. Linked transducer, i.e. a linear variable density transformer to sense the probe movement and produce a related electrical signal. Sample furnace, programmers and various output devices. 

One area of analytical chemistry which is currently developing rapidly is the automation of methods. Some degree of automation has been used for a number of years in instruments such as automatic burettes coupled to absorptiometric or electrometric end-point detectors, and in data output devices which provide continuous pen recording or signal integration facilities. The major features of recent developments include the scope for instrumental improvements provided by solid-state electronic circuits and the increasing application of digital computers (Chapter 13). 

The IR detectors are usually connected to a controller that supplies power to the detectors and acts as a signal processor and output device. A typical controller monitors up to four detectors and energizes an output when any one of the detectors senses IR radiation that exceeds the alarm threshold level. The controller also contains the circuitry that checks the detectors and electrically supervises the interconnecting wiring to the explosive squibs or solenoid valves by trickling a small current through the external circuits. 

The traditional HPLC instrument is composed of two different parts the first part separates the components of the sample and the other part accomplishes the detection of the components separated. The part of the HPLC carrying out the separation contains a column, an injection device and the eluent delivery system (pump with filters, degasser and transfer tubing, eventually a mixer for gradient elution). One or more detectors, a signal output device coupled with appropriate software, are responsible for detection and primary data evaluation. Pumps deliver the eluent or the different components of the eluent into the column with a precise, constant and reproducible flow rate. 

A DCS is also used to control Area 400. The DCS monitors and controls the cycling of the TRBPs, the preheaters, the GPCR reactors, the scrubbers, and the product gas handling system. Each of these subsystems is controlled with a series of control loops tied to the individual control functions through input devices linked to output devices via control algorithms within the DCS. 

Compounds are expressed by their symbolic formulas. The use of the full ASCII character set allows the elements to be expressed by their usual one or two character names, with the upper or lower case context providing the character count. More elaborate designations for atoms (including superscripts denoting isotope number, for example) are accommodated by enclosing the expression in appropriate quotes. Upshift and downshift metacharacters can be used here to denote appropriate character placement on output devices (such as plotters and typesetters) which allow for partial line spacings line printers would ignore them. 

Output displays will be required to bring the abstract aspects of voluminous output data into some form that appeals to the experience of the user. Isopleth maps are useful, as are three-dimensional isometric plots like SYMVu, produced by Harvard University. Printer plots of concentration maps will undoubtedly enjoy an even greater application, because of the common availability of line printers or teletypewriters as output devices. Examples of these techniques are symap and grid, both produced by Harvard University. 

Power for the control panel should be provided with a suitable uninterrupted power supply (UPS). The panel will provide a DC current to field detectors. This power will enable the panel to monitor all input circuits, output circuits, and trouble signals within the detectors, such as shorts, ground faults, and detector disconnects. It will also provide an AC powering signal to field output devices. All output circuits should be similarly supervised for trouble. An example alarm and detection control panel is shown in Figure 7-18. 

From the late 1930s to the mid-1960s, the second generation appeared. These instruments used sensors to convert chemical or physical properties into electrical signals. Electrical circuits were then employed to produce meaningful data (Fig. 8.3). Analysts interacted with these instruments using knobs and switches to obtain data from output devices such as analogue meters and strip chart recorders. 

An NMR spectrum is effectively a graph of the intensity of absorption of Rf radiation (y-axis) against the frequency of the Rf radiation (x-axis). Since frequency and magnetic field strength are linked by the Larmor equation, the x-axis could also be calibrated in units of magnetic field strength. In a CW NMR spectrometer, the x-axis of the output device (usually a pen plotter) is coupled to the frequency sweep so that the response of the sample is displayed as the frequency of the Rf transmitter varies. 

The majority of MAECIS is written in FORTRAN with a few assembler routines for database management. The program is currently running on a VAX 11/780 computer system and uses Tek-ronix 4025 graphics terminals as the primary input/output devices. MAECIS is a command oriented program that has a built in prompt mechanism to assist the user with commands. It also has a HELP section that provides the user with detailed online instructions. 

Assume that a quantity of interest ( score ) can be written as a real-valued function P t) = F[p(f)] of the system state Q f) at a given time t. This might be, for example, a measure of performance of some input-output device that is supposed to operate within a predefined cycle/gafe time t. Depending on fhe physical problem and model chosen, exfensions and generalizations are conceivable, such as a comparison of the outcome for different t (on a timescale set by a constraint)... 

Clicking this button opens the Printer Setup dialog box through which the user can select the output device from a list of all devices known to the MS-WINDOWS operating environment. 

Closes the Page Layout dialog box and opens the Print dialog box. As well as printing the page layout, this dialog box contains options to select and configure the output device (see section 4.7.4.)... 

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