Frequency scaling


I have an application in which I need to use a frequency output from an RTC (Chronodot) to drive a clock-like mechanism that needs to revolve 360 degrees in a particular time. The mechanism has a mechanical reduction ratio that is ill-defined due to the hybrid friction-drive technique. I will likely have to find a frequency value that works by experimentation. So I need to find a way of scaling an output from the RTC so that I can fine tune it to get the proper result. Any thoughts about this will be welcome.

How many PPM error in the drive signal is acceptable? Why?

What range of frequency are you talking about? Hz? kHz? MHz?

...and what range of RPM? If you prefer to lurk and just want a generic answer, it's "a software PLL".