le travail à l'écran de visualisation work with display units

ADJUSTABILITY RANGES FOR VDT WORKSTATIONSMarvin J. Dainoff, James Balliett, Phillip N. Goernert, James McCarthy and Leonard S. MarkCenter for Ergonomie Research and Department of Psychology, Miami University, Oxford, OhioTo optimize the fit between the VDU operator and workstation, we require a sufficient degree of flexibilitysuch that body orientations/postures at operator-workstation interfaces (e.g., eyes, fingers, buttocks,feet) require a minimum effort to be maintained. In the practical implementation of this approach, itis necessary to specify exact ranges of adjustability of workstation components so as to afford optimumpostures for a given fraction (typically 5th percentile female to 95th percentile male) of a givenpopulation.In the United States, a consensus standard for VDU workstation has recently appeared (AmericanNational Standard for Human Factors Engineering of Visual Display Terminai Workstations: ANSI/HFS100-1988.) In this paper, we examine some of the complexities which arise in application of thisstandard while simultaneously attempting to optimize two independent ergonomie criteria. We proposean algorithmic approach to this solution.Statement of the Problem: ANSI/HFS 100-1988 defines two general requirements: (a) Seat pan heightmust conform to the operators' popliteal height, (b) Keyboard support surface must fall within specifiedranges of forearm and upper arm angles.An analytic solution, in terms of specific ranges of seatpan and worksurface adjustable which meetsboth of these general requirements is relatively straightforward for the case of the 90-degree uprightposture. However, two complications arise.(a) The above solution for keyboard support surface assumes that the upper arm is in the superiorfrontal plane. This is unrealistic for actual working postures.(b) The 90-degree posture is, itself, considered an unrealistic idealization (Grandjean, Mandai, Kroemer).Actual working postures involve either forward or backward trunk angles.Solution: A series of trigonometric equations have been derived which define a new anthropometricdimension, seated fingertip height (Pheasant), which can be used to specify an optimum worksurfaceheight. These equations can be used to define an envelope of heights which include: upper and lowerranges of popliteal heights, upper and lower ranges of finger tip heights assuming no forward flexionof the upper arm, and upper and lower ranges of finger tip heights assuming a 25-degree shoulderflexion (the maximum allowable according to Chaffin and Andersson).KEYWORDS: ANSI/HFS 100-1988 standards for VDT workstations, workstation adjustability, optimumworksurface height.USA.AN EVALUATION OF THE PROPOSED ISO PERFORMANCE-BASED TESTMETHOLOGY FOR INPUT DEVICES.Knight, D.*, Milner, N.P.* and Fielding, I.***User Interface and Design Evaluation Group, British Telecom ResearchLaboratories, Martlesham Heath, Ipswich, IP5 7RE, Suffolk, U.K."""Department of Computer Science, University of Technology,Loughborough, Leicestershire, LE11 3TU .The International Standards Organisation (ISO) has proposed a performance-basedtest method to assess the usability of keyboards. British Telecom was one of four teamswho agreed to use the draft method to compare different keyboards and report thefindings to ISO/TCI59/SC4/WG3, the working group co-ordinating the drafting ofstandards for input devices.The research at British Telecom's Research Laboratories compared a BT Merlin 5000keyboard, which passes the measurement-based ISO ergonomie standard, with thesame model of keyboard which had had the key depression forces altered such that itwould not meet the currents standards. The normal keyboard was called the referencekeyboard and the altered keyboard was termed the test keyboard. Four subjects tookpart in the main study. Data was collected about the amount of data input from eachkeyboard and the number of errors made. Opinion scores were also collected in theway outlined in the draft.The results showed that less data could be input via the test keyboard than the referencekeyboard. The test proposed method (which used sequential testing) failed the testkeyboard with the performance data from the four subjects. The opinion scores wereless sensitive although uniformly biased towards the reference keyboard.A number of concerns were noted with the method which included :-• the way that errors are handled.• the excessive duration of the experiment.• the lack of a reference test for subject performance on consecutive days.In conclusion, the principle to provide a performance-based ergonomie test method issupported. The practical problems with the draft make it unsuitable for use in itscurrent form. Changes are suggested based on BT's empirical work.KEYWORDS:Keyboards, Standards, conformance testing.TEV 1989 — DEUXIÈME CONFÉRENCE SCIENTIFIQUE INTERNATIONALE • MONTRÉAL • SECOND INTERNATIONAL SCIENTIFIC CONFERENCE — WWDU 1989172TEV 1989 — DEUXIÈME CONFÉRENCE SCIENTIFIQUE INTERNATIONALE • MONTRÉAL • SECOND INTERNATIONAL SCIENTIFIC CONFERENCE — WWDU 1989173