Flow measuring apparatus

Claim 1

IN AN APPARATUS FOR MEASURING FLUID FLOW, THE COMBINATION COMPRISING A PAIR OF THERMALLY SENSITIVE ELEMENTS DISPOSED IN A FLUID STREAM, HEATING MEANS FOR MAINTAINING A TEMPERATURE DIFFERENTIAL BETWEEN SAID SENSITIVE ELEMENTS INCLUDING ELECTRICALLY OPERABLE INDIRECT HEATING MEANS POSITIONED IN HEAT EXCHANGE RELATIONSHIP WITH ONE OF SAID THERMALLY SENSITIVE ELEMENTS, A NETWORK FOR PRODUCING AN ELECTRICAL OUTPUT SIGNAL PROPORTIONAL TO THE MAGNITUDE OF THE FLUID FLOW, SAID NETWORK INCLUDING A BRIDGE MEANS HAVING SAID THERMALLY SENSITIVE ELEMENTS CONNECTED AS TWO ARMS THEREOF AND HAVING ADJUSTING MEANS FOR BALANCING THE BRIDGE FOR OPERATING FLOW CONDITIONS WHEREBY FLOW OF THE FLUID COOLS ONE OF SAID ELEMENTS AND DISTURBS THE TEMPERATURE DIFFERENTIAL BETWEEN SAID ELEMENTS TO UNBALANCE THE BRIDGE MEANS AND PRODUCE AN ELECTRICAL OUTPUT FROM SAID BRIDGE, SAID NETWORK ALSO INCLUDING FEEDBACK MEANS ELECTRICALLY COUPLED TO SAID BRIDGE MEANS AND TO SAID ELECTRICALLY OPERABLE HEATING MEANS AND RESPONSIVE TO THE OUTPUT ELECTRIC CURRENT FROM SAID BRIDGE MEANS TO CONTROL THE HEATING ELECTRIC CURRENT SUPPLIED TO SAID ELECTRICALLY OPERABLE INDIRECT HEATING MEANS TO MAINTAIN SAID TEMPERATURE DIFFERENTIAL, A CURRENT MEASURING DEVICE CONNECTED IN CURRENT RELATIONSHIP WITH SAID HEATING MEANS FOR DERIVING AN OUTPUT INDICATION OF THE VALUE OF HEATING CURRENT SUPPLIED TO SAID HEATING MEANS AS A MEASURE OF FLUID FLOW, AND ELECTRICALLY OPERABLE MEANS COUPLED TO SAID BRIDGE MEANS AND SAID HEATING MEANS FOR LINEARIZING THE RESPONSE OF THE APPARATUS AT LOW FLOW RATES BY VARYING THE TEMPERATURE DIFFERENTIAL BETWEEN SAID ELEMENTS IN RESPONSE TO VARYING FLOW CONDITIONS.