That "ground" has to sink how much current at what voltage?
Is that voltage AC or DC?
Then operation wise:
How often is this 4.5 V adjustment going to be made?
It's the difference of taking a voltmeter and setting the voltage with a trimmer and then put the voltmeter away,
Could be a turns-counting dial and a display.
Could be a display in engineering units?
Could be a Up/Dn pushbutton sort of thing?
Do you want it to be a commercial product?
Here
https://www.aliexpress.com/i/32947646340.html is a place to start.
Here
https://www.aliexpress.com/item/329...earchweb0_0,searchweb201602_,searchweb201603_ is a real example of what you COULD want?
You'll have to wait for it.
Just a note, 0-5V can be "hard" to come by because with a 5V supply and no trickery, you can't get to zero and you can;t get to 5V. getting to a few hundred mV of the rails is easier.
We go with real specifications, not made up ones.
We can take the programming design approach where you propose a system based on loose specs and then ask questions.
Resolution plays apart of it too. 4 to 4.9V could give you better resolution if you need it.
Thanks for the 12V supply being available.
process control stuff generally will work, but that stuff is rugged and EXPENSIVE.
How fast the signal needs to be generated may matter.
The process control module IAMS with limits MIGHT work for you. It will take 24VDC or AC power, do engineering units, do the "alarms" all in one module. You just don't want to change the value every day.
Your "block diagram" consists of a:
A reference
A buffer
a potentiometer
A comparitor with/without hysteresis
The output z of your signal matters. If it's 100 ohms or 1M, it makes a difference.
Getting that 0-5 reference is tough. Getting a 100mV to 4.9V is not as hard.