Gas exchange system flow configuration
Inventors
Johnson, Mark A. • Eckles, Robert D. • McDermitt, Dayle K.
Assignees
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Publication Number
US-9482653-B2
Publication Date
2016-11-01
Expiration Date
Abstract
Active compensation designs to offset the impact of gas diffusion sources and sinks in a photosynthesis and transpiration measurement system are disclosed. A sensor head for use in a gas exchange analysis system includes an active, piezoelectric flow splitting device for splitting a flow between a sample chamber and bypass pathway. The active flow splitting device is controlled by feedback from a downstream flow meter. A continuous measurement system for rapidly and accurately surveying large numbers of samples is described.
Core Innovation
The disclosed invention relates to a gas exchange analysis sensor head apparatus for open photosynthesis/transpiration measurement in which an active flow splitting device variably splits an incoming gas flow between a sample path and a reference/bypass path. The sample chamber receives the gas from the active flow splitting device through a coupled inlet, and a first gas analyzer measures the concentration of gas exiting the sample chamber outlet. In parallel, the second output port provides a reference/bypass stream to a second gas analyzer that measures the concentration of the gas exiting the second output port.
To stabilize and accurately control the concentration differential measured in an open system, the apparatus includes a flow meter and a feedback control circuit. The flow meter measures the flow rate of gas entering the sample chamber or the flow rate of gas entering the second gas analyzer, and the feedback control circuit controls the active flow splitting device to adjust the gas flow to a selected output port responsive to the flow meter signal, thereby controlling the split ratio.
The invention addresses diffusion-driven parasitic CO2/H2O sources and sinks by placing the active flow splitting mechanism proximal to the sample/leaf chamber, thereby reducing diffusion parasitic contributions. The document also describes comparing analyzer measurements to account for diverted gas and supports measurement by integrating the concentration differential over time in an open-path system.
Claims Coverage
The partial claims include two independent claims. Each independent claim centers on an active, variably controlled flow splitting device coupled with two gas analyzers and flow-meter feedback to regulate the split ratio for gas concentration differential measurement.
Active variably controlled flow splitting device with dual outputs
An active flow splitting device having a first output port and a second output port configured to variably split an incoming gas flow between the first and second output ports.
Sample chamber directly coupled to first output port
A sample chamber having an inlet and an outlet, the inlet coupled with the first output port of the active flow splitting device and the outlet coupled to a first gas analyzer measuring a concentration of gas exiting the outlet.
Dual gas analyzers measuring concentration in split streams
A first gas analyzer coupled with the outlet of the sample chamber and configured to measure a concentration of gas exiting the sample chamber outlet, and a second gas analyzer coupled with the second output port of the active flow splitting device and configured to measure a concentration of gas exiting the second output port.
Flow meter placement between splitter and first analyzer inlet with feedback control
A flow meter coupled between the first output port of the active flow splitting device and the inlet of the sample chamber, the flow meter configured to measure a flow rate of gas entering the inlet of the sample chamber, and a feedback control circuit adapted to control the active flow splitting device to adjust the gas flow provided to the first output port responsive to a flow rate signal from the flow meter.
Flow meter directly coupled between second output port and second analyzer
A flow meter directly coupled with and between the second output port of the active flow splitting device and the second gas analyzer, the flow meter configured to measure a flow rate of gas entering the second gas analyzer.
Feedback control adjusts gas flow to second output port
A feedback control circuit adapted to control the active flow splitting device to adjust the gas flow provided to the second output port responsive to a flow rate signal from the flow meter.
Across the independent claims, the core inventive coverage is the combination of an active flow splitting device that controllably variably splits an incoming gas flow, two gas analyzers measuring concentrations in the split streams, and a flow meter with a feedback control circuit that adjusts gas flow to one split branch responsive to a measured flow rate.
Stated Advantages
Reducing diffusion-driven parasitic CO2/H2O sources and sinks by placing the flow splitting mechanism proximal to the sample/leaf chamber.
Stabilizing the flow for accurate concentration differential measurements in an open-path system.
Improving measurement of concentration differential by nearly an order of magnitude through diffusion-error mitigation using flow splitting at the head.
Documented Applications
Open-path photosynthesis/transpiration measurement systems that measure concentration differentials using a sample chamber and a reference/bypass pathway with two gas analyzers.
Measuring concentration differential in an open-path system by integrating the concentration differential over time.
Interested in licensing this patent?