Like the previous comments, the dimmers can be used but I would look at building in an additional fail safe option to prevent disaster should you wish to use it as opposed to standard on/off heat control.
I use the dimmer option in this setup:
The dimmer provides what I refer to as a poorman's proportional control to the heat pad. The digital controller monitors temperature shuts off supply once high point is reached. This also prevents overheating in the event the dimmer fails.