Fluid flow sensing and control method and apparatus

An aircraft having a plurality of autonomous air flow sensing and control units each operable independent of the others and associated with a specific air flow conduit for controlling the air flow rate with the associated conduit, each unit comprising:

• a housing fixed to the conduit;
• a sensing probe extending from the housing into the conduit for monitoring the air flow through the conduit having an electrically heatable member in good heat transfer relation with the associated air flow, a first temperature sensitive resistor within the probe solely thermally contacting in good heat transfer relation with the heatable member, and a second temperature sensitive resistor within the probe remote from and thermally isolated from the electrically heatable member and in good heat transfer relation with the associated air flow;
• and
• a flow controller located closely adjacent the housing and responsive to the air flow sensed by the sending probe for controlling the air flow through the conduit.

A proves of sensing and controlling flow of a fluid through a conduit, comprising the steps of:

• providing a probe containing a first temperature sensitive resistor and a second temperature resistor within the probe;
• providing a measure of the temperature of the fluid passing through the conduit;
• exposing an electrically heatable element to the flow of fluid, the electrically heatable element being within the probe;
• providing the first temperature sensor resistor in close proximity to the electrically heatable element, and solely thermal contacting the heatable element;
• providing the second temperature sensitive resistor remote from the electrically heatable element and thermally insulated from the electrically heatable element;
• supplying an electrical current to the element to maintain the temperature of the element at a determined temperature by exposing another resistor having substantially linear resistance vs. temperature characteristics to the element, measuring the resistance of the exposed another resistor, and utilizing the measure of the temperature of the fluid passing through the conduit and the measured resistance to vary the electrical current supplied to the element;
• measuring the current supplied to the element;
• utilizing the measure of current to provide a control signal
• utilizing the control signal to control the rate of fluid flow;
• and
• performing all the foregoing steps at a location closely adjacent the conduit.