I've been looking into a specific piece of equipment called a 'present weather sensor' that uses a sensor looking at a sample in air to determine the visibility and current weather (i.e. rain, snow, etc.). From what my research, I've found a expired patent from a company that currently makes these sensors, Vaisala. This is the expired patent. I also found a new patent for what seems to be the same exact thing here. As I mentioned before, this company still makes these sensors. However, there are a few other companies making seemingly identical pieces of hardware, like Campbell Scientific, and Biral.
Could someone explain how these companies are able to produce and sell these without infringing on the patents of the original company?