Optimum Knob Crowding

Abstract

Reach time, turning time, and inadvertent touching of adjacent controls (i.e., errors) were measured while a standard setting was made with one of several closely spaced knobs. The variables manipulated were spacing between knobs, knob diameter, and knob configuration. Performance improved rapidly with increasing distance between knob edges up to an interperipheral distance of 1 in., after which performance continued to improve but at a much slower rate. For equal amounts of panel space consumed by several closely crowded knobs, ¼-in. diameter knobs were more nearly error free than were the larger diameter knobs tested. For equal distances between knob edges, however, performance improved with increasing knob diameter. These results apply only to knobs capable of being operated by moderate torque. It was found that the frequency with which a crowding knob is inadvertently touched is strongly affected by the angular position which it occupies with respect to the operated knob but is practically independent of the presence of other crowding knobs at the same distance from the operated knob.