Do Dracal USB sensors log data when they are not connected to a USB port, or do they need to be connected to log data?

No, Dracal sensors are not data loggers. They generate data but do not store any of it. The data must be viewed and recorded in real time either through our DracalView graphical software or through one of our many data integration tools.

However, our SensGate gateway does store data locally.