Flow sensor
OwnerOsman K. Mawardiinventor
Life of this patent
Estimating the term…
Abstract
A flow-sensing system is provided which employs a pair of sensing resistors. One of the resistors is disposed within flowing fluid, while the other is shielded from the flow. The sensor resistances are held constant by identical feedback circuits which maintain the relationship between current values in the sensors for this purpose. The required difference in currents in the two resistors enables fluid flow to be computed. Input and output temperature sensors are provided to enable temperature difference to be measured and combined with fluid-flow to indicate the rates of BTU flow. One temperature sensor and the fluid-flow sensors constitute an assembly miniaturized in a solid state chip.
Claims13
Fluid flow rate measuring apparatus comprising first and second identical resistors with a common support, in contact with said support and supporting the first resistor exposed to the fluid, flow rate of which is to be measured, thus being in thermal relation to such fluid at substantially the temperature thereof, means for shielding the second resistor from exposure to the fluid connections to both resistors to supply electric current to them, means for adjusting the relative values of electric currents in the resistors to maintain them at the same temperature, whereby the difference in electric current flow is indicative of heat loss from the first resistor to the fluid by convection, and means for measuring the difference in electric currents.
A unit for apparatus responsive to rate of flow of fluid in a fluid stream comprising a slab in the stream, the slab having a cavity therein having an opening, a first resistor in the cavity, a shield in the cavity between the first resistor and the cavity opening, maintaining the first resistor out of contact with the fluid, a second resistor in the cavity exposed to fluid stream, means for heating the resistors, and means for comparing heat loss from the resistors.
Fluid flow rate measuring apparatus comprising first and second resistors, means for supporting the resistors with the first resistor exposed to the fluid, flow rate of which is to be measured, means for shielding the second resistor from the fluid, connections to both resistors to supply electric current to them, and means for adjusting the relative values of electric currents in the resistors to maintain them at the same temperature, whereby the difference in electric current flow is indicative of heat loss from the first resistor to the fluid by convection, and means for measuring the difference in electric currents, wherein the resistor supporting means comprises a slab with a cavity therein with an opening toward the fluid, with the second resistor located in the cavity, the first resistor being located between the second and the opening of the cavity, and wherein a wafer is provided in the cavity between the two resistors, of sufficient size to close the cavity between the two resistors, and thereby shield the first resistor from the fluid.
Dependencies are inferred from the claim text.