I don't like the way it looks.
It's too thick (hard to put in a pocket to carry around) and too wide - i get it that you want to use two fingers to spin those wheels but still.
It's not like it can stay on the desk like that, you have to lift it to move those wheels around and when you're on your feet at a desk you'd probably want to lay the thing flat so that the screen points up.
Are those wheels tactile, do you feel some resistance when advancing a 1/8th? Some click, audible feedback etc ? How well do those work with gloves on? How about dust going into the device ?
A multimeter or phone style format would seem to make more sense and maybe you'd be able to use just 4 buttons and a mode / set button to keep costs lower ... < ... > mode < .... > or a couple dpads ( left - right changes value, up down changes measurement unit, middle = reset )
ex
https://www.digikey.com/product-detail/en/panasonic-electronic-components/EVQ-Q3AA15/P12330SCT-ND/593493with a more phone/multimeter style look, maybe you could design ruler on the edge or something like that and have a second purpose, or maybe have a measuring tape come out from the edge
With a 16:9 format, you could squeeze a 320x240 oled or even higher resolution lcd monitor and have bigger text
As is, the box is big enough you'd easily fit buttons ... the classic 0 to 9 and a dot and 2-3 other buttons would be enough.
push button for first number , push button for 2nd number ... use dot to go between the parts of the number ex type 1.1.16 to enter 1 1/16 or ..4 to change the 1 1/16 to 1 1/4
Guaranteed it would be faster than moving that wheel with super fine control and double checking yourself when you see those fractions change.
Look at your keyboard numeric pad ... have all the things you need there... 0..9 , +,- , * , / , num lock can become select number (first or second) ... people are used to that layout.
Less moving parts, cheaper, microcontroller can start up on keypress and less accidental turn on in your pocket or less damage prone if you bump into something while the thing is on your waist depending on button size and spacing you can press them with gloves, you can make a small sound when pressing the buttons for feedback...
add a white led and some lens at the top and use it as flashlight... you could replace the single aa with 2 AAA rechargeable or a flat lithium that can be recharged through usb once every 2 weeks or a month ... ex
https://www.digikey.com/product-detail/en/adafruit-industries-llc/2011/1528-1857-ND/6612469Looks like it will break in pieces if it falls off a desk on hard cement... how it handles actual construction jobs. Think rubber corners or something, or add metal inserts for screws on the case.