what you want to do is impossible with App Inventor Bastien. The only way to know for sure is to experiment if you have the necessary technical skills. I provided a link to an extension that uses OTG to link to an arduino. . Will it work to allow you to query your keyboard to get information from "3 dial indicators" ? I have no idea.
How to proceed? I do not know. What you do depends on how where the 'dial indicator' information comes from . Based on this
I think this is probably impossible with App Inventor especially not knowing what protocol is used to send the data. Does this gauge have a Bluetooth output? App Inventor might communicate with it if output is Bluetooth compatible.