You can check the plugin-status going to to the PluginHandler-Section of the Server/Status-Page. You will find an information similar to:
system-Sail_Instrument present:['AWA', 'AWS', 'COG', 'HDM', 'HDT', 'LAT', 'LON', 'SOG', 'STW', 'VAR'] --> calculated:['AWAF', 'AWD', 'AWDF', 'AWSF', 'CRS', 'DEV', 'DFT', 'DFTF', 'GWA', 'GWD', 'GWS', 'HDC', 'HEL', 'LAY', 'LEE', 'LEF', 'POLAR', 'SET', 'SETF', 'TWA', 'TWAF', 'TWD', 'TWDF', 'TWDMAX', 'TWDMIN', 'TWS', 'TWSF', 'VMCA', 'VMCB', 'VMG', 'VPOL'] sending:['$CAHDG', '$CAMWD', '$CAMWV', '$CAVDR'], leeway estimation, laylines from table, VPOL, VMC
present[...]: already available signals
calculated[...]: calculated signals
sending[...]: sent NMEA-sentences
and some additional informations about calculation details.
(for the abbreviations take a look at the table in Calculated-Data ).