This sensor simply connects to one of the 3 motor wires on a brushless motor to measure the RPM.
When configuring the brushless RPM sensor in the UniLog or UniTest 2, the correct number of impulses per revolution must be specified for the RPM measurement. For the optical and magnetic sensors this is the number of propeller blades or magnets. For the brushless speed sensor you need to configure the number of motor poles. For instance a typical in-runner motor has 2 poles while outrunners commonly have 14 poles. Check with your motor manufacturer if you are unsure.
For gear drives, the gear ratio can be configured in the software so that the actual propeller RPM is given.