Differential pressure responsive signal circuit

Claim 1

A SYSTEM FOR PROVIDING AN OUTPUT RESPONSE UPON VARIATION IN THE RATE OF A FLID FROM A PREDETERMINED RATE OF FLOW, COMPRISING A RESISTANCE SENSING ELEMENT HAVING A RELATIVELY HIGH TEMPERATURE COEFFICIENT POSITIONED TO HAVE THE FLOWING FLUID IMPINGE THEREON WHEREBY THE RESISTANCE OF THE ELEMENT VARIES WITH THE RATE OF FLOW, AN ELECTRICAL CIRCUIT INCLUDING INPUT MEANS TO SUPPLY A SIGNAL CURRENT TO SAID ELEMENT AND BEING OPERABLE TO PRODUCE A NULL OUTPUT RESPONSE AT A PREDETERMINED RESISTANCE OF SAID ELEMENT AND TO PRODUCE AN OUTPUT RESPONSE PROPORTIONAL TO VARIATION OF THE RESISTANCE OF SAID ELEMENT FROM THE PREDETERMINED VALUE, AND A PRESET CONSTANT INPUT HEAT SOURCE INCLUDING A THERMISTOR AND AN ADJUSTABLE POWER SUPPLY CONNECTED TO CONTINUOUSLY SUPPLY BIAS CURRENT TO THE THERMISTOR SEPARATE FROM THE CURRENT THROUGH THE ELEMENT AND FROM THE FLUID FOR SUPPLYING A PRESELECTED AMOUNT OF HEAT TO SAID ELEMENT TO BIAS IT TO A PREDETERMINED TEMPERATURE, AND CIRCUIT MEANS CONNECTED TO THE ELECTRICAL CIRCUIT TO DETECT SAID OUTPUT RESPONSE IN THE PRESENCE OF THE SIGNAL CURRENT THROUGH THE SENSING ELEMENT AND THE PRESET BIAS CURRENT FLOW FROM SAID ADJUSTABLE POWER SUPPLY TO THE THERMISTOR AND THE FLUID FLOW OVER THE SENSING ELEMENT.

Claim 2

A SYSTEM FOR PROVIDING AN OUTPUT RESPONSE UPON VARIATION IN THE RATE OF A FLID FROM A PREDETERMINED RATE OF FLOW, COMPRISING A RESISTANCE SENSING ELEMENT HAVING A RELATIVELY HIGH TEMPERATURE COEFFICIENT POSITIONED TO HAVE THE FLOWING FLUID IMPINGE THEREON WHEREBY THE RESISTANCE OF THE ELEMENT VARIES WITH THE RATE OF FLOW, AN ELECTRICAL CIRCUIT INCLUDING INPUT MEANS TO SUPPLY A SIGNAL CURRENT TO SAID ELEMENT AND BEING OPERABLE TO PRODUCE A NULL OUTPUT RESPONSE AT A PREDETERMINED RESISTANCE OF SAID ELEMENT AND TO PRODUCE AN OUTPUT RESPONSE PROPORTIONAL TO VARIATION OF THE RESISTANCE OF SAID ELEMENT FROM THE PREDETERMINED VALUE, AND A PRESET CONSTANT INPUT HEAT SOURCE INCLUDING A THERMISTOR AND AN ADJUSTABLE POWER SUPPLY CONNECTED TO CONTINUOUSLY SUPPLY BIAS CURRENT TO THE THERMISTOR SEPARATE FROM THE CURRENT THROUGH THE ELEMENT AND FROM THE FLUID FOR SUPPLYING A PRESELECTED AMOUNT OF HEAT TO SAID ELEMENT TO BIAS IT TO A PREDETERMINED TEMPERATURE, AND CIRCUIT MEANS CONNECTED TO THE ELECTRICAL CIRCUIT TO DETECT SAID OUTPUT RESPONSE IN THE PRESENCE OF THE SIGNAL CURRENT THROUGH THE SENSING ELEMENT AND THE PRESET BIAS CURRENT FLOW FROM SAID ADJUSTABLE POWER SUPPLY TO THE THERMISTOR AND THE FLUID FLOW OVER THE SENSING ELEMENT.