meters per unit of time upon receipt of a request from the main loop step 371 the efm 10 converts gas flow data from metric to imperial units or vice versa step 372 and writes the converted data to a display buffer step 373 mmc card routine 380 fig5 g is used to download gas flow data onto an mmc card the efm 10 first senses whether an mmc card has been inserted in the card reader of the efm 10 step 381 if so the efm 10 automatically downloads all fully corrected gas flow measurement data as determined in aga 8 routine 350 since the last time a card was inserted step 382 the date and time of the present card insertion is then stored step 383 the mmc card may also store the serial number of the efm 10 and its unique pre programmed well specific identifier button routine 390 fig5 h is initiated when it is desired to read data stored in the rom 11 b of the efm 10 directly from the digital display screen 24 of the efm 10 the efm 10 can be programmed to display a variety of stored data values and the user can toggle through these values by repeatedly depressing either the internal display button 26 or the external display button 28 of the efm 10 upon sensing that either the internal display button 26 or the external display button 28 has been depressed step 391 the efm 10 checks a status counter to determine what data value corresponds to the display button 39 s current u201c toggle u201d position step 392 and writes the corresponding.