You have a BGE, right? Definitely throw away the dial thermometer that came with it. Dialing in and controlling your dome temp is just a matter of time and experience. I have this thermometer
https://www.thermoworks.com/Smoke . it works pretty well, but I don’t use it most of the time. You will get used to knowing roughly where the grill temp is, using the heat shield or not, raising or lowering the grill surface to control the cook and then just using a thermapen or similar to monitor the meat temp.
If you have a BGE, there is a separate thread where you might get better help.