Quote Originally Posted by AdrianW View Post
Cheers - those VFDs look like great value. Do you have a link for the guy selling encoders? The minimum recommended spec is 8000p/r (seems excessive?) and even the 2000p/r ones I've found are in the hundreds of quid.
What's currently fitted to drive the spindle?
Any VFD should be useable with. Only issue would be if the spindle has a DC motor, and a basic non-isolated KBIC style speed controller.

Encoder wise, you need to differentiate between counts/edges per revolution, and pulses/lines per revolution. The 8000 spec will mean counts per revolution, which translates to a 2000 ppr/lines per revolution.
What you're looking for is an "incremental rotary encoder" with a minimum of 2000 ppr/lines, however I'm not sure if the Acorn requires single ended, or differential output (a differential output encoder can be used to drive single ended inputs, but a single ended output encoder would need a differential driver to drive differential inputs). They can be had on eBay for under £40, although you may need to do a bit digging into specs to ensure they do meet the required minimum spec.