I haven't got a picture of one we made, but get a LR bottle jack.
From below, in the very centre, drill and tap a 1/8 bsp. Plumb this into a gauge of your choice - voila - you now have an hydraulic jack scale.
This is the table i came up with, using a 1.25" bore. This is when the small part of the ram isn't extended, only the thicker one. (LR jacks are telescoping)
Edit : it's not a simple task of copying a spreadsheet from excel onto the forum !