Video display unit

The first set of case studies illustrates errors due to the inadequate design of the human-machine interface (HMI). The HMI is the boundary across which information is transmitted between the process and the plant worker. In the context of process control, the HMI may consist of analog displays such as chart records and dials, or modem video display unit (VDU) based control systems. Besides display elements, the HMI also includes controls such as buttons and switches, or devices such as trackballs in the case of computer controlled systems. The concept of the HMI can also be extended to include all means of conveying information to the worker, including the labeling of control equipment components and chemical containers. Further discussion regarding the HMI is provided in Chapter 2. This section contains examples of deficiencies in the display of process information, in various forms of labeling, and the use of inappropriate instrumentation scales. 

Source Triphenyl phosphate was identified as a component in outer covers of brand-new computer video display units. Concentrations were estimated to be 8 to 10 and 0.3 to 0.5 wt % in 4 and 6 video display units, respectively. The concentrations of triphenyl phosphate in the remaining 8 video display units were <0.02 wt % (Carlsson et al., 2000). 

Carlsson, H., Nilsson, U., and Ostman, C. Video display units an emission source of the contact allergenic flame retardant triphenyl phosphate in the indoor environment, Environ. Sci. Technol, 34(18) 3885-3889, 2000. 

TV, video display units, induction heaters Induction heaters, electronic surveillance Radio AM, FM, and TV broadcasting Mobile telephony GSM (European standard)... 

Common sources of low-level exposure to electromagnetic fields are electric and magnetic powered transport (static fields), overhead power lines, domestic electric appliances (ELF), antitheft electronic devices, or video display units (in very low to low... 

A generalized schematic of a DCS is shown in Figure 15.15. A number of local control units (LCUs), which contain shared microprocessors, perform the control functions for the process in a distributed fashion. Each local control nnit has several consoles attached to it. The consoles (video display units, VDUs), which ntilize cathode ray tubes (CRTs), have video displays that show process schematics with current process measnrements. Operators and control engineers nse these displays to monitor the behavior of the process, set up control loops, and enter setpoints and tuning parameters. Normally, these consoles have touch screen capability so that, if operators want to make a change to a control loop, they touch the icon for the desired controller. Then a screen pops... 

Fig.7. Scheme of the instrumentation for mapping tunnelii -induced photoemission on a metal surface. DAC = digital/analog converter PMT - photomultiplier VDU = video display unit Aux = auxiliary input I f = reference current. 

Recording elements These are used to provide a visual demonstration of how a chemical process behaves. Usually, the variables recorded are the variables that are directly measured as part of the control system. Various types of recorders (temperature, pressure, flow rate, composition, etc.) can be seen in the control room of a chemical plant, continuously monitoring the behavior of the process. The recent introduction of digital computers in the process control has also expanded the recording opportunities, through video display units (VDUs). 

Replot the spectrum on a video display unit or on paper. 

Meters with calibrated scales were used for readout in early AA instruments. Nowadays, digital displays and graphical presentation of signals on the screen of video display units are used. Analytical results can be made as a hard copy on a chart recorder, a printer, or a plotter. A typical hard copy of the analytical results is shown in Figure 27. 

Applications and uses surgical probes, pharmaceutical process equipment manifolds, high-frequency insulators used in microwave communications equipment, clamps used to connect printed circuit boards to video display units used in airplanes, tanks, and ships. 

Qualified display processing cabinets, which receive inputs from qualified input signal cabinets and the integrated protection cabinets. This data is displayed in the main control room and remote shutdown area on qualified video display units. 

NUREG/CR-4221, "Human Engineering Guidelines for the Evaluation and Assessment of Video Display Units", U.S. Nuclear Regulatory Commission, July 1985. 

VDU video display unit visual display unit... 

Both EdF reference sets of EOPs have four separate procedures for the reactor operator, for the water and steam (turbine) operator, for the shift supervisor (containing a combination of reactor, water and steam operator procedures) and for the safety engineer. All procedures are in the colour flow chart format (paper based). The recent four loop N4 plants have fully computerized procedures (with computerized operating actions actuated from the operator video display units) as well as a complete backup paper based set of procedures for operating from the auxiliary panel if the computer system fails. 

Maximum illuminance levels for video display units (VDUs) 500 lux... 

The supervision and control system displays information in the reactor operating console to help reactor operation during normal or abnormal conditions, providing operators clear and concise information. This information display is arranged hierarchically in the video display units, according to functionality and priority... 

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