The proliferation of the Windows operating system has spurred test and measurement manufacturers to incorporate Windows-based graphical user interfaces into their instruments. This familiarity is valuable because design engineers may leverage their understanding of interface elements such as menus, toolbars and dialog boxes when operating such GUI-based test equipment as oscilloscopes and logic analyzers. This reduces the engineer's need to learn a specialized interface and contributes to ease of use.
Beyond that basic familiarity, however, claims that Windows means automatic ease of use deserve scrutiny. Ironically, the power of a Windows interface makes it easy to implement bad designs. For example, if controls aren't named descriptively and arranged in logical groupings, no amount of graphical bells and whistles can save the design.
Test and measurement instruments typically have small displays. Their operation is interactive, with dynamic control adjustments and information displays, and the viewing of real-time data is critical. All this affects their ease of use.
Conventional dialog boxes, where most controls are provided in Windows applications, are usually "modal," meaning that until the dialog box is dismissed, no user interactions with the rest of the system are possible. Furthermore, control changes in dialog boxes don't actually take effect until the dialog box is dismissed. Finally, conventional dialogs block the information behind them while they are active. Those aspects of traditional dialog box behavior lead to problems with ease of use, as Agilent Technologies discovered during design testing of its family of Windows-based oscilloscopes.
Customers told us they often interacted with other elements of the user interface after invoking a dialog box, but before making the dialog's control changes. They wanted control changes to be fast, and they asked us to exercise care with large or multiple open ("modeless") dialogs so they wouldn't obscure the waveform display area.
In response, we created a control system where dialogs are neither purely modal nor purely modeless. When a dialog is active, other system interactions are permitted, but when the user invokes another dialog, the first one is automatically closed. Control changes take effect immediately, and dialogs may be rendered in a semitransparent or fully transparent manner.
Our experiences with Windows-based test equipment provide lessons for test and measurement instrument designers and purchasers. Windows is a powerful tool, but be forewarned: Windows alone does not guarantee ease of use.
Jay Alexander is R&D Section Manager for Agilent Technologies Inc. (Colorado Springs, Colo.).
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