Fluid sampling system

Details Fluid sampling system Fluid sampling system

1998-02-13

2001-06-05

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Control element responsive to a sensed operating condition

C422S068100, C422S082130, C422S083000, C422S093000, C422S105000, C422S082120, C073S863310, C073S863330, C073S863860, C073S863710

Reexamination Certificate

active

06241950

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to systems that measure parameters of a fluid.
The sampling of fluid within a system allows the fluid to be tested for concentration of various substances. Typically, the fluid within an environmental system such as the air in an office building or a hospital is monitored to determine the level of pollutants such as carbon monoxide and carbon dioxide in the system. The information obtained during the monitoring can be used to control a heating ventilation and air conditioning (HVAC) system, e.g., to control indoor air quality (IAQ). In one approach to monitoring IAQ, remote sampling systems are connected to various locations in the system by a network of tubes that shunt fluid to a central location where in-line measurements are made on air components. In other monitoring systems, sensors are distributed throughout a building and electronically communicate with a central controller.
In addition to monitoring the level of pollutants, it is desirable to monitor and control the flow of pollutants such as carbon monoxide (CO), carbon dioxide (CO
2
), odors, and dust by monitoring and controlling the fluid flow within the system. Thus, the pressure within the system, especially the pressure differential between two locations within the system, often is measured to determine fluid flow within the system. For example, pressure differentials across the external walls of a building are important to maintain a positive indoor pressure, especially at the lower levels of a building where negative pressures are more likely to form due to the buoyant force of heated air. The positive indoor pressure prevents air from entering the building as a draft and forces outdoor air to be introduced through the HVAC system where it is conditioned properly and filtered. Because pressure differentials within a building dictate the flow of air, they are important in the control of contaminants in sterile environments as in hospitals. In addition, pressure differentials across the wall of an air duct can be used to determine volumetric airflow within a component of an environmental system.
A typical method for measuring pressure includes connecting pressure sensors to various locations within the system and comparing the pressure measurements to determine the magnitude and direction of fluid flow. A set of sensors may be used at each location with each sensor being most accurate in a different range.
SUMMARY OF THE INVENTION
One aspect of the invention is a fluid sampling device that includes a manifold having a plurality of inputs, a common purge pathway, a common sampling pathway, a plurality of valves to couple and decouple some inputs to the common purge pathway and other inputs to the common sampling pathway. The system also includes a differential pressure sensor coupled to the common sampling pathways.
Preferred embodiments of this aspect include the following features.
A controller connected to the plurality of valves produces control signals that enable the valves to couple and decouple the inputs to the common pathways. The controller produces control signals to configure the valves such that one of the valves couples an input to the common sensor pathway, another one of the valves couples a different input to the common purge pathway, and a set of valves decouples the common pathways from other inputs. The controller produces control signals to cause the differential pressure sensor to measure differential pressure across the common pathways. The differential pressure sensor either is two individual sensors coupled to one each of the common pathways, or is a plurality of sensors that measures pressure in different pressure ranges. The controller causes the pressure sensors to each measure differential pressure across the common sampling pathway and the common purge pathway to provide indications, e.g., an electronic or other signal, of the differential pressure between the input ports.
In another aspect of the invention, a manifold has multiple input ports, at least two common output ports, and a set of valve pairs. Each pair of valves corresponds to an input port. One of the valves of the pair couples and decouples the input port to one output port, and the other valve of the pair couples and decouples the input port to the other output port. A differential pressure sensor is coupled between the two output ports.
In another aspect of the invention, a manifold has two common pathways and at least one input port. The manifold has a plurality of passages, and the input port is in fluid communication with one common pathway through one of the passages. A valve is disposed along the passage and is capable of blocking the flow of fluid between the input port and the common pathway. A pressure sensor is disposed across the sensor pathway and the purge pathway.
Preferred embodiments of this aspect of the invention include the following features.
A second valve is disposed along another passage and is capable of blocking the flow of fluid between the input port and the second common pathway. Another input port is in fluid communication with one of the common pathways through a third passage and is in fluid communication with the other common pathway through a fourth passage. Third and fourth valves are disposed along the third and fourth passages respectively. Both valves are capable of blocking the flow of fluid between the second input port and one of the common pathways. A controller is connected to the first, second, third and fourth valves, and can configure the valves such that the first valve couples the first input port to the first common pathway, the fourth valve couples the second input port to the second common pathway, the second valve decouples the first input port from the second common pathway, and the third valve decouples the second input port from the first common pathway. In an alternate arrangement, the controller can configure the valves such that the second valve couples the first input port to the second common pathway, the third valve couples the second input port to the first common pathway, the first valve decouples the first input port from the first common pathway and the fourth valve decouples the second input port from the second common pathway.
In another aspect of the invention, a manifold has at least two output pathways and at least two input ports. One input port is in fluid communication with one output pathway through one passage of a plurality of passages, and another input port is in fluid communication with another output pathway through another of the passages. A valve of a plurality of valves is disposed along each passage and has a coupled and a decoupled position. A differential pressure sensor is disposed across the output pathways. A sample tube establishes fluid communication between a sample zone and one of the input ports. A sensor is connected to one of the output pathways, and a system controller operates the system.
In another aspect of the invention, a method for measuring differential pressure in a fluid sampling system includes three steps. First, fluid is sampled from a sample zone, through a manifold. The manifold has at least two inputs, at least two outputs, and a plurality of passageways. The inputs are in fluid communication with at least one output through a passageway. A set of valves are disposed along the passageways and have coupled and decoupled positions. Second, the valves are opened such that an output is in fluid communication with a sample zone and another output is in fluid communication with another sample zone. Third, the pressure difference across the two coupled outputs are measured.
Preferred embodiments of this aspect of the invention include the following features.
The pressure difference across the outputs is measured with a plurality of pressure sensors. The pressure difference is processed based both on the value of the sensor indications and on a plurality of pressure ranges that correspond to the pressure sensors.
In another aspect of the invention, a method for oper

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