For the price, you can't beat the Heidenhain , it is an accessory to a Heidenhain DRO, but you can buy it separately, I think the current price is under $1k.
But the words 'Professionally built' and 'Cheap' do not usually go together.
This is a professional unit, and very accurate.
It requires a 5vdc supply but you can condition it to 24v with an extra transistor.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.