The picture shows the control panel of the microwave at work. It’s hard to figure out at first glance whether the microwave really has that much functionality or whether a limited set of functions is presented in a rather complicated manner. (At least the manufacturer seems to have thought of the pizza aficionados.)
Issues With The Control Panel
The upper knob is interesting for at least two reasons.
The knob and its “scale” seem to imply some sort of continuum on which a certain value can be adjusted. In fact, it’s no continuum at all. The user can choose one of six options by turning the know to the respective position. In addition, it’s not even one single dimension that can be adjusted here: the knob is used for controlling the microwave functionality and the integrated grill.
The symbology used for those two functionalities is the second noteworthy thing: the wave-like symbols refer to…the grill. The first three symbols from the right indicate: upper&lower heat, lower heat, upper heat. If you mistake those for the microwave functionality, you could be in for a nasty surprise when preparing a foil-sealed microwave meal.
Apart from using better symbols to refer to the two functionalities, it would be an improvement using a different control for setting them in order to avoid the impression (and false mental model) that the main purpose of this area is setting the degree/intensity for one single parameter. An approach could consist in providing two distinct controls, one for setting microwave and one for grill, and allowing the user to combine the two settings as required. One would have to make sure that invalid combinations are properly communicated or avoided, respectively. Adding some labels could help, too. (For manufacturers, the charm of symbol-only panels lies in the fact that they don't have to be localized, of course.)
Other Examples of Microwave Usability Issues
As it seems, there's still enough reason for usability engineers to get active in microwave oven design. Some other examples for microwave usability issues can be found in the following places:
Microwave Usability (Raymond Cassick)
Microwave Oven Usability (Steve Krause)