DPI isn't the SIZE of the image, it's the amount of information "DOTS PER INCH" which MAKES UP the image.. the higher the DPI, the higher the quality (and bigger file size) of the scan.
First of all, don't use the crappy Windows scanning wizard. You need to get a program like photoshop etc that has a buttload more options.
How big are the dials, do they fit in the area of an A4 page? If so, once you've scanned it with a decent program (which might even allow you to scan to a specified size) resize that image to fit an A4 page.
It will take some experimentation, although it's not all that hard to do.
Good Luck :lmao:
</printboy>