A flow sensor comprises a flow restriction disposed within a passage such that a fluid passing through the passage must pass through the flow restriction. The flow sensor also has an upstream pressure sensor coupled to the passage at a point upstream of the flow restriction and configured to measure and provide an upstream pressure of the fluid within the passage, a downstream pressure sensor coupled to the passage at a point downstream of the flow restriction and configured to measure and provide a downstream pressure of the fluid within the passage, and a temperature sensor coupled to the passage and configured to measure and provide a temperature of the fluid within the passage. The flow sensor also includes a flow sensor processor coupled to the upstream and downstream pressure sensors and the temperature sensor and configured to accept measurements therefrom and calculate a compensated flow rate based at least in part on the measured pressures and temperature.
1. A flow sensor comprising:
a flow restriction disposed within a passage such that a fluid passing through the passage must pass through the flow restriction;
an upstream pressure sensor coupled to the passage at a point upstream of the flow restriction and configured to measure and provide an upstream pressure of the fluid within the passage;
a downstream pressure sensor coupled to the passage at a point downstream of the flow restriction and configured to measure and provide a downstream pressure of the fluid within the passage;
pressure sensor electronics coupled to the upstream pressure sensor and the downstream pressure sensor and configured to determine a pressure drop measurement;
a filter coupled to the passage upstream of the upstream pressure sensor;
a temperature sensor coupled to the passage upstream of the filter and configured to measure and provide a temperature of the fluid within the passage;
a package for housing the upstream pressure sensor, the downstream pressure sensor, the pressure sensor electronics, and the temperature sensor, wherein the upstream pressure sensor is connected to the passage through a first gas passage, the downstream pressure sensor is connected to the passage through a second gas passage, and the temperature sensor is connected to the passage through a feed-through connected to the passage upstream of the filter;
a non-volatile memory configured to store compensation parameters which characterize flow resistance characteristics of the flow restriction, the compensation parameters comprising a pressure drop of at least one predetermined fluid characterized for the flow restriction; and
a flow sensor processor coupled to the memory, the upstream and downstream pressure sensors and the temperature sensor and configured to accept measurements therefrom and calculate a compensated flow rate based at least in part on the measured pressures and temperature.
2. The flow sensor of claim 1 , wherein:
the non-volatile memory is configured to store executable instructions;
the flow sensor processor is configured by retrieving the executable instructions from the memory to further retrieve the compensation parameters from the memory; and
the calculation of the compensated flow rate is based at least in part on the retrieved compensation parameters.
3. The flow sensor of claim 2 , wherein:
the flow sensor processor is further configured to accept an identification of the fluid that is passing through the passage;
the compensation parameters comprise characteristics of the flow restriction that are related to a plurality of predetermined fluids;
the retrieved compensation parameters comprise characteristics of the flow restriction related to the identified fluid; and
the calculation of the compensated flow rate is based at least in part on the retrieved compensation parameters that are related to the identified fluid.
4. The flow sensor of claim 3 , wherein the characteristics of the flow restriction are predetermined for each of the plurality of predetermined fluids.
5. The flow sensor of claim 4 , wherein the plurality of predetermined fluids comprises one or more medical gases.
6. The flow sensor of claim 5 , wherein the plurality of predetermined fluids comprises one or more of a standard composition of ambient air, a pure oxygen, and a heliox gas mixture.
7. The flow sensor of claim 4 , wherein the characteristics of the flow restriction are predetermined for each of the plurality of predetermined fluids over a range of temperatures.
8. The flow sensor of claim 7 , wherein the range of temperatures comprises at least 5-50° C.
9. The flow sensor of claim 1 , wherein the flow restriction comprises a porous disk.
10. The flow sensor of claim 1 , further comprising a temperature sensing element connected to the temperature sensor through the feed-through.
11. A ventilator comprising:
a sensor configured to detect a number and placement of at least one magnet of a gas inlet adapter, the number and placement of the one or more magnets associated with a gas;
an output flow channel configured to mate with a supply limb;
an input flow channel configured to accept the gas from a source; and
a flow sensor comprising:
a flow restriction disposed within a passage coupled between the input flow channel and the output flow channel such that the gas passing through the passage must pass through the flow restriction;
an upstream pressure sensor coupled to the passage at a point upstream of the flow restriction and configured to measure and provide an upstream pressure of the gas within the passage;
a downstream pressure sensor coupled to the passage at a point downstream of the flow restriction and configured to measure and provide an downstream pressure of the gas within the passage;
pressure sensor electronics coupled to the upstream pressure sensor and the downstream pressure sensor and configured to determine a pressure drop measurement;
a filter coupled to the passage upstream of the upstream pressure sensor;
a temperature sensor coupled to the passage upstream of the filter and configured to measure and provide a temperature of the gas within the passage;
a non-volatile memory configured to store compensation parameters which characterize flow resistance characteristics of the flow restriction, the compensation parameters comprising a pressure drop of at least one predetermined fluid characterized for the flow restriction;
a flow sensor processor coupled to the memory, the upstream and downstream pressure sensors and the temperature sensor and configured to accept measurements therefrom and calculate a compensated flow rate based at least in part on the measured pressures and temperature; and
a package for housing the upstream pressure sensor, the downstream pressure sensor, and the pressure sensor electronics, the temperature sensor, and the flow sensor processor, wherein the upstream pressure sensor is connected to the passage through a first gas passage, the downstream pressure sensor is connected to the passage through a second gas passage, and the temperature sensor is connected to the passage through a feed-through connected to the passage upstream of the filter.
12. The ventilator of claim 11 , wherein:
the non-volatile memory is configured to store executable instructions;
the flow sensor processor is configured by retrieving the executable instructions from the memory to further retrieve the compensation parameters from the memory; and
the calculation of the compensated flow rate is based at least in part on the retrieved compensation parameters.
13. The ventilator of claim 12 , further comprising:
the gas inlet adapter having the at least one magnet associated with the gas being supplied to the input flow channel; and
a central processor coupled to the sensor and the flow sensor processor, the central processor configured to identify the gas that will be passing through the flow sensor from the detected orientation of the gas inlet adapter, wherein:
the flow sensor processor is further configured to accept an identification of the gas that is passing through the flow sensor, the identification based on the number and placement of the at least one magnet of the gas inlet adapter;
the compensation parameters comprise characteristics of the flow restriction that are related to a plurality of predetermined gases;
the retrieved compensation parameters comprise characteristics of the flow restriction related to the identified gas; and
the calculation of the compensated flow rate is based at least in part on the retrieved compensation parameters that are related to the identified gas.
14. The ventilator of claim 13 , wherein the characteristics of the flow restriction are predetermined for each of the plurality of predetermined gases.
15. The ventilator of claim 14 , wherein the plurality of predetermined gases comprises one or more medical gases.
16. The ventilator of claim 15 , wherein the plurality of predetermined gases comprises one or more of a standard composition of ambient air, a pure oxygen, and a heliox gas mixture.
17. The ventilator of claim 14 , wherein the characteristics of the flow restriction are predetermined for each of the plurality of predetermined gases over a range of temperatures.
18. The ventilator of claim 17 , wherein the range of temperatures comprises at least 5-50° C.
19. The ventilator of claim 11 , wherein the flow restriction comprises a porous disk.
20. The ventilator of claim 11 , further comprising a temperature sensing element connected to the temperature sensor through the feed-through.