Kestrel Meter Interface - Serial Port - 0804SER - 730650000050 The Kestrel Interface is the ideal companion to the Kestrel 4000 Pocket Weather Tracker or 4100 Pocket Air Flow Tracker . With the optional computer interface data can be uploaded for long-term storage in-depth analysis and detailed charting. Simply connect the interface cable to the serial port on your PC rest the Kestrel 4000 or 4100 on the cradle and upload your stored data.