Tag Archives: Control-display ratio

Control Sensitivity in Design

I run into the problem everyday: when I try to adjust the temperature of my shower, it is just way too sensitive. I have to move the lever as carefully as I can, however, it still surprises me with sudden change of temperature. I end up taking a shower either too cold or too hot.

This occurs to me today because I read about “control-display ratio” today when I went over the human factor class that I am taking this semester. Control-display (C/D) ratio is measuring the change of control compared to the change of display (or outcome, response). If the C/D ratio is high, then the control sensitivity is low, and vise versa. C/D ratio is very important for HCI design as well. Low C/D ratio (high sensitivity) could save time when users are approaching the target, while high C/D ratio (low sensitivity) could help user with fine adjustment when they reach the target area. So a carefully designed C/D ratio is important for improving user controlling experience. For example, the movement of mouse or controlling stick should have a reasonable C/D control so that users could minimize the effort when they try to move their mouse to reach a target.

The following is a common example in our everyday life: when you try to adjust the window, cursor has to be moved within a narrow area in order to change the shape. If the control sensitivity is too high, it will be very very annoying.