The new Nasa Marine EML ~2 Electromagnetic NMEA Speed Log. Speed through water with no moving parts. The EML ~2 electromagnetic speed log measures the boat speed through the water with no moving parts. Robust and accurate, the sensor generates an alternating magnetic field below the boat and measures the resulting electric field produced by the boat moving through the water. With excellent linearity and a resolution of 0.1 Knot, over the range 0.2 to 40 Knots, the control box converts the sensor signal to boat speed, trip and total distance and send it to any compatible NMEA 0183 display. Features: Simple to install Speed range 0.2 ~ 40 Knots Speed, trip and total logs NMEA 0183 output sentences VLW + VHW Standard 50mm diameter transdcuer Cable length 5.0m In the box: Transducer and control box with instructions