CN1701224A - Low power gas leak detector - Google Patents

Abstract

A leak detector having a multi-stage pre-concentrator, consisting of an array of heater elements which desorb analytes in a phased manner, in synch with the sample stream, to maximize sensitivity. The heater elements of the pre-concentrator are coated with adsorber material on both sides of the heater elements, i.e., top and bottom sides, and have small anchor points to minimize power dissipation. The concentrated gas mixture output of the concentrator is electronically injected into a separator, which for separates the constituents of the detected analyte-fluid and recognizing the nature or source of the analyte.

Description

Low Power Gas Leak Detector

background

This application claims priority to US Provisional Patent Application No. 60/414,211, filed September 27, 2002, entitled "Phase Control Sensor," which is incorporated herein by reference.

The present invention relates to the detection, identification and analysis of gases. Related art combustible gas leak detectors may be low cost (and in part have reasonable sensitivity), yet cannot identify the nature of gas leaks (natural gas, biogas, propane or gasoline vapor), while other devices such as portable GC ( Gas Chromatographs) have moderate sensitivity and are capable of discriminating gases, but they are very expensive, slow (response time greater than about 10 seconds), and consume a lot of power.

Various aspects related to the construction and processing of gas detectors are disclosed in U.S. Patent No. 6,393,894, issued May 28, 2002, entitled "Gas Sensor with Phased Heater with Enhanced Sensitivity," which Incorporated herein by reference; and US Patent No. 4,944,035, issued Jul. 24, 1990, entitled "Thermal Conductivity and Specific Heat Measurement," which is incorporated herein by reference.

summary

Gas leak detectors and analyzers are enabled by affordable, in-situ, ultra-sensitive, low-power, low-maintenance and compact trace detectors and analyzers that wirelessly Or send the detection and/or analysis results to the central or other manual control stations through another medium (such as wires or optical fibers). Microfluidic analyzers can incorporate phased heater arrays, concentrators, and separators as enhanced detectors, thereby increasing the availability of low-cost multi-gas analyzers and systems for providing gas leak detection.

The gas leak detector is low power, fast, compact, low cost, intelligent, wireless or non-wireless, low maintenance, robust and highly sensitive. It is a phased heater based leak detector that responds in about a second, uses less than a watt of power, is able to identify the nature of the gas by its composition, and is palm-sized so it is very portable.

The heating element of the phased heater array can be coated with adsorption material on its two surfaces, the top surface and the bottom surface, to achieve low power consumption and more efficient heating of the input detection gas. The heating element can have a narrower width for this less power consumption. There is also a heater membrane comprising a reduced number of anchor points for less heat conduction from the heating element.

The surfaces of the internal channels of the heater array may be coated with a non-absorptive insulating layer, except those surfaces specifically designed to be coated with an adsorbent material. The thickness of the adsorptive coating or film can be reduced, thereby shortening the time required for adsorption and desorption. A relatively economical pump can be used to draw a sample of the fluid to be checked in order to detect possible gas leaks from somewhere. Low power electronics that sleep when not in use may be used. Therefore, the leak detector consumes very little power.

Gas leak detectors can be integrated on-chip through conventional semiconductor processes or micro-electromechanical systems (MEMS) technology. Such processing results in low power consumption, compactness, and in situ arrangement characteristics of the detector. The flow rate of the air or gas sample through the detector can be very small. In addition, sample carrier gas is not necessary, so this absence of carrier gas reduces dilution of the sample being tested, and also eliminates the maintenance and required volumes associated with the handling of high pressure gas tanks. This approach allows the sensor to provide rapid analysis and prompt results, potentially at least an order of magnitude faster than some related art devices. It avoids the delays and high costs of labor-intensive laboratory analysis techniques. The sensor is intelligent, it can have an integrated microcontroller for the analysis and determination of the detected gas, and maintain accurate and successful operation, as well as transfer information to and from unattended remote locations. Sensors can communicate detector information, analysis and results via public lines or optical or wireless media and are capable of full duplex communication with host systems over long distances with "plug and play" adaptation and simplicity. The system can work through the network. It can be interconnected with other gas sample conditioning devices (particulate filters, valves, flow and pressure sensors), local maintenance control points, and can provide gas leak monitoring via the Internet. This detector is robust. It maintains accuracy in high electromagnetic interference (EMI) environments, such as in the vicinity of power distribution substations with very strong electric and magnetic fields. The detector has high sensitivity. It provides sub-ppm (parts per million) level detection, which is 100 to 10,000 times better than related art technologies such as conventional gas chromatographs which can provide sensitivities in the 1 to 10 ppm range. Among them, the detector is a lower power, faster, more compact and more sensitive and affordable variant of the gas chromatograph. It also consumes less power and is faster than existing models of existing types of phased heater detectors that require heavy batteries that must be charged and discharged multiple times, while the detector of the present invention avoids this battery. The detector of the present invention has structural integrity and has very low or no risk of leakage in applications of detecting and analyzing high pressure fluid samples over a very large differential pressure range.

In a leak detector, a small pump such as a Honeywell MesoPump ^TM preferably draws the sample into the system, but only a portion of the sample flows through the phased heater sensor at a flow rate controlled by a valve (could be a Honeywell MesoValve ^TM or a Hoerbiger PiezoValve ^TM ) . This method allows for rapid sample acquisition over a long sampling path and provides a regulated flow of approximately 1 to 3 cc/min to the leak detector. The pump of the leak detector can be arranged to draw sample gas through the filter so that fast sample collection and regulated flow through the phased heater sensor can be provided.

When the sample pump draws sample gas past the leak detector, the gas expands, thus increasing its volume and linear velocity. The control circuitry can be designed to compensate for this speed change in order to keep the heater "wave" in sync with the changing gas speed in the sensor. To compensate for the change in volume of the sample gas as it is forced through the heater channels, the heater electronics need to adjust the flow control and/or the speed of the heater "wave" so that the internal gas flow velocity remains in line with the heater "wave" Synchronize.

During leak checking operations, the detector's capability (similar to any other slower GC) detects a wide variety of trace components of air, such as about 330 to 700 ppm CO ₂ , about 1 to 2 ppm CH ₄ , and about 0.5 to 2 ppm 2.5% _H2O . This allows the output elution time to be calibrated on-line and to check for the presence of other peaks such as ethane, propane or other gas pipeline leaks that may represent natural gas. Therefore, the ratio of the peak heights of the sample gas components may reveal clues about the origin of trace gases including automobile exhaust or gasoline vapors.

Sensors can have sensitivity, speed, portability, and low power that make them especially useful for safety-mandated periodic leak checks of natural or propane gas along transmission or distribution piping systems and other gases in chemical plants.

In its leak detection application, the sensor uses some or all of the sample gas constituents (and their peak ratios) as calibration markers (elution times identify the nature of the gas constituents) and/or leak source identification. If there is only a certain peak such as methane (which is present in mountain air at a concentration of about 1 to 2 ppm), then there is not enough information to indicate that the composition is derived from biogas, natural gas or pipeline gas or other fluids.

The leak sensor can be used as a portable device or installed at a fixed location. Compared with comparable sensors in related fields, it is more compact than portable flame ionization detectors, does not require bulky hydrogen tanks, is faster and more sensitive than hot wire or metal oxide combustible gas sensors, and is more efficient than traditional and And/or portable gas chromatographs are faster, more compact and more energy efficient.

Brief introduction to the drawings

Figure 1 is a block diagram of a possible leak detector monitoring system;

Figure 2 shows the details of the trace gas detector setup;

Figure 3 is a layout showing the principle of operation of an exemplary sensor device;

FIG. 4 is a side cross-sectional view of the exemplary sensor device of FIG. 3;

5 is an end cross-sectional view of the exemplary sensor device of FIG. 3;

Figure 6 is a graph showing exemplary heater temperatures and also showing corresponding concentration pulses generated at each heating element of the sensor device;

Figure 7 is a graph showing several heating elements to illustrate the gradual increase in analyte concentration;

Figure 8 is a graph showing concentration pulses to a concentration level of about 100%;

Figure 9 is a layout of another exemplary sensor assembly;

Figure 10 is a schematic diagram of how the sensor can be used to sample a fluid stream (e.g. flue gas) for gas composition analysis;

Figure 11 is a timing diagram showing the operation of the sensor assembly shown in Figure 10;

Figure 12 is a basic layout of an integrated circuit including sensors, concentrators, separators and sensors; and

Fig. 13 is a table showing different power consumption levels for various parts of the gas leak detector.

describe

FIG. 1 shows an exemplary view of a low power leak detector system 11 . An input fluid 25 from the ambient space or volume 41 may enter a conduit or tube 19 connected to the input 34 of the low power leak detector 15 . Fluid 25 may be processed by detector 15 . Processed fluid 37 may exit output 36 of detector 15 and be discharged via conduit or tube 39 into a volume at any location indicated. The term "fluid" is used as a general term which includes both gaseous and liquid substances. Results or findings can be sent to microcontroller/processor 29 for analysis. Microcontroller or processor 29 may send various signals to detector 36 for control, adjustment, calibration or other purposes. Analytical calculations, results or other information may be sent to modem 35 for conversion into a signal for transmission to station 31 via wire, fiber optic or other similar medium. In addition, this output to the modem 35 may alternatively or simultaneously be sent to the transmitter 33 for wireless transmission to the station 31 together with information about the actual position of the detector obtained, for example via GPS, especially when it is used as case of portable devices. Additionally, station 31 may send various signals to modem 35 and receiver 33, which may be passed to microcontroller or processor 29 for control, adjustment, calibration, or other purposes.

FIG. 2 shows a trace gas device 15 . A sample stream 25 containing gas from a possible leak source enters from the tube or suction tube 19 into the input port 34 . A particle filter 43 is provided here for removing dirt and other particles from the flow of fluid 25 entering the device 15 . This removal is to protect the device and filtration should not reduce the device's ability to accurately analyze the composition of fluid 25 . Dirty fluids (non-volatile particles with suspended solids or liquids) can impair proper sensor function. A portion 45 of fluid 25 may flow through differential thermal conductivity detector or sensor 127 while another portion 47 of fluid 25 flows through tube 49 to one-way valve 51 . By placing the "T" tube in close proximity to the inlet 45, sampling can be achieved with minimal time delay, since the relatively high flow rate of stream 47 helps to shorten the flushing time of the filter. Pump 53 may cause fluid 47 to flow from the output of particulate filter 43 through tube 49 and valve 51 . Regulator valve 51 controls the flow through the sensor via tube 45 by regulating the suction pressure of pump 55 in tube 129 . The flow configuration described above thus achieves both benefits at the same time. These benefits include minimal sampling latency and flow control. Pump 55 flows fluid 45 from the output of filter 43 through detector 127 , concentrator 124 , flow sensor 125 , separator 126 , thermal conductivity detector or sensor 128 and tube 129 . Pump 55 pumps fluid through tube 57 to tube 59 where fluid 45 and fluid 47 are combined into combined fluid 61 . A pump 55 can be used in the system, depending on the pumping capacity of the pump 53 (10-300 cc/min) and a sufficiently low flow rate of the pump 55 (0.1-3 cc/min). Fluid 61 is pumped to output port 36 by pump 53 . Fluid 61 exits via outlet pipe 39 as stream 37 . Data from detectors 127 and 128 may be sent to controller 130, which in turn forwards the data to microcontroller and/or processor 29 for processing. The resulting information can be sent to station 31 .

FIG. 3 is a schematic diagram of that portion of sensor device 10 or 15 representing concentrator 124 or separator 126 in FIG. 2 . The sensor device may include a substrate 12 and a controller 130 . Controller 14 may or need not be incorporated in substrate 12 . Substrate 12 may have a plurality of thin film heating elements 20, 22, 24 and 26 thereon. While only four heating elements are shown, any number of heating elements may be provided, for example between 2 and 1000, but typically in the range of 20-100. Heating elements 20, 22, 24 and 26 may be made of any suitable electrical conductor, stable metal or thin film alloy, such as a nickel-iron alloy, sometimes called permalloy, having a composition of 80% nickel and 20% iron and platinum, platinum silicide, and polysilicon. The heating elements 20 , 22 , 24 and 26 are disposed on a thin, low thermal mass, low in-plane thermal conduction support 30 as shown in FIGS. 4 and 5 . The support or diaphragm can be made of Si ₃ N ₄ or other suitable or similar material. The heating element may be made of Pt or other suitable or similar material.

4 and 5 show a two-channel phased heater mechanism 41 having channels 31 and 32 . Substrate 12 and portion or wafer 65 have defined channels 31 and 32 for receiving flow-through sample fluid 45 . The channels may be processed by selectively etching the silicon channel wafer or substrate 12 below the support 30 and the channel wafer or portion 65 above the support. The channel may include an inlet port 34 and an outlet port 36 for streaming sample fluid 45 .

The sensor device may also include a plurality of interactive elements positioned within the channels 31 and 32 so as to be exposed to the flow sample fluid 45 . Each interactive element may be arranged adjacent to a corresponding heating element, ie in the closest possible contact. For example in FIG. 4 , interactive elements 40 , 42 , 44 and 46 may be disposed on the lower surface of support 30 within channel 32 and adjacent to heating elements 20 , 22 , 24 and 26 , respectively. Additionally, interactive elements 140, 142, 144, and 146 may be disposed on the upper surface of support 30 within channel 31 and adjacent heating elements 20, 22, 24, and 26, respectively. Other channels with additional interactive film elements may also be provided, which are not shown in this illustrative example. Interactive elements can be formed from a variety of membranes commonly used in liquid or gas chromatography, such as silica gel, polymethicone, polydimethylsiloxane, polyethylene glycol, porous silica, Nanoglass ^TM , activated carbon, and Other similar polymeric substances. Furthermore, the above-mentioned interactive species can be modified by appropriate dopants to achieve different degrees of polarity and/or hydrophobicity for optimal adsorption and/or separation of target analytes.

FIG. 5 shows a cross-sectional end view of the phased heater mechanism 41 . The support 30 may be attached to the top structure 65 . The anchor 67 can fix the position of the support 30 relative to the channel 31 . Fewer attachment points for anchors 67 reduces thermal conduction losses from support 30 to the rest of structure 41 . This example has fewer anchor points compared to common anchoring methods, which results in a saving of about 1.5 times the remaining heating element input power.

An interactive thin film element can be formed by flowing a material laden with the desired sorbent through channel 32 . This provides an interactive layer throughout the channel. If a separate interactive element is desired, selective "development" can be performed by providing the coating with a temperature change via heating elements 20, 22, 24 and 26. After the coating has been developed, solvent flow may be provided through channel 32 to remove the coating at any location other than that which has been developed or polymerized with a suitable solvent such as acetone so that only the solvent adjacent to the heating element Material. A coating 65 of non-absorptive insulating material may be applied to the inner walls of the channels 31 and 32, except where designed there are sorbent-coated surfaces such as interactive elements. This coating reduces the required heating element power by about 1.5 times. The thermal conductivity of these materials should be much lower than that of the material used for the channel walls. The material used for the channel walls may be silicon. Alternative materials for coating 65 may include silicon dioxide or other metal oxides. The coating 65 can reduce the power used by the heating elements in the support 30 . A reduction or reduction in the size (width, length and thickness) of the heating element membrane as well as the adsorption membrane can result in about a four-fold reduction in power while maintaining a reasonable ratio of mobile/stationary phase volume. The reduced or reduced thickness of the adsorption film shortens the time required for adsorption-desorption and saves about 1.5 times the energy required for each fluid analysis. Use this particularly economical yet adequately functional pump 53 and/or 55 and 120 and low power electronics for the controller 130 and/or microcontroller/processor 29 (which are in sleep mode when not in use) Resulting in an approximately two-fold reduction in such power, the aforementioned pumps 53 and/or 55 and 120 are run approximately 1 second or less prior to the start-up of the concentrator and/or the measurement cycle of the analyzer system 11 .

The table in FIG. 13 shows the overall power required to run a leak detector system 11 similar to a system of about 100 milliwatts or less with an analysis cycle every three seconds with the design features described above. As shown in the table, the energy saving measures of the system 11 can reduce the energy required per analysis (once every three seconds) from about 1.7 joules and a peak power of about 1280 milliwatts to about 0.4 joules and a peak power of 220 milliwatts .

Controller 14 or 130 may be electrically connected to each heating element 20, 22, 24, 26 and detector 50, as shown in FIG. The controller 14 or 130 may energize the heating elements 20, 22, 24 and 26 through a phase sequence (see lower part in FIG. 6) such that an upstream concentration pulse generated by one or more upstream interactive elements reaches the interactive While at the interactive element, each respective interactive element 40 , 42 , 44 and 46 is heated and desorbs selected components into the flow sample fluid 45 . Any number of interactive elements may be employed to achieve the desired concentration of the constituent gases in the concentration pulse. The resulting concentration pulses may be provided to detectors 50, 128, 164 for detection and analysis. Detector 50, 127, 128 or 164 may be a thermal conductivity detector, a discharge ionization detector, or any other type of detector such as is commonly used in gas or liquid chromatography.

Figure 6 is a graph showing exemplary heater temperatures and corresponding concentration pulses generated at each heating element. As described above, the controller 14 or 130 energizes the heating elements 20, 22, 24 and 26 in a time phase sequence. Exemplary phase heater temperatures for heating elements 20 , 22 , 24 and 26 are shown as temperature curves or lines 60 , 62 , 64 and 66 , respectively.

In the example shown, controller 14 , 130 ( FIG. 3 ) may first energize first heating element 20 to increase its temperature, as shown by line 60 in FIG. 6 . Since the first heating element 20 is thermally connected to the first interactive element 40, the first interactive element desorbs selected components into the flow sample fluid 45, generating a first concentration pulse 70 at the detector 128 or 50 or 164 , if no other heating elements are pulsed. The flow sample fluid carries the first concentration pulse 70 downstream towards the second heating element 22 as indicated by arrow 72 .

Controller 14 (or 130) then energizes second heating element 22 to increase its temperature, as indicated by line 62, beginning at or before the energy pulse on element 20 has ceased. Since the second heating element 22 is thermally connected to the second interactive element 42, the second interactive element also desorbs the selected component into the streaming sample fluid 45, generating a second concentration pulse. The controller 14, 130 can energize the second heating element 22 such that the second concentration pulse substantially overlaps the first concentration pulse 70, thereby producing a higher concentration pulse 74, as shown in FIG. The flow sample fluid carries a larger concentration pulse 74 downstream towards the third heating element 24 as indicated by arrow 76 .

The controller 14, 130 then energizes the third heating element 24 to increase its temperature, as shown by line 64 in FIG. Since the third heating element 24 is thermally coupled to the third interactive element 44, the third interactive element 44 can desorb selected components into the flow sample fluid, generating a third concentration pulse. The controller 14, 130 can energize the third heating element 24 so that the third concentration pulse substantially overlaps the larger concentration pulse 74 provided by the first heating element 20 and the second heating element 22, thereby producing an even higher concentration pulse. Concentration pulse 78. The streaming sample fluid 45 carries this larger concentration pulse 78 downstream towards the Nth heating element 26 as indicated by arrow 80 .

The controller 14 , 130 then energizes the Nth heating element 26 to increase its temperature, as indicated by line 66 . Since the Nth heating element 26 is thermally connected to the Nth interactive element 46, the Nth interactive element 46 can desorb selected components into the flow sample fluid 45, generating the Nth concentration pulse. The controller 14, 130 can energize the Nth heating element 26 such that the Nth concentration pulse substantially overlaps the larger concentration pulse 78 provided by the preceding N-1 interactive elements. The flow sample fluid carries the Nth concentration pulse 82 into the separator 126 or detector 50 or 128 or 164, as described below.

As noted above, heating elements 20, 22, 24, and 26 may have a common length. Thus, by providing the same voltage, current or power pulse to each heating element, the controller 14, 130 can achieve the same temperature of the heating elements. The voltage, current or power pulses may have any desired shape, including triangular, square, bell-shaped or any other shape. The temperature profiles 60 , 62 , 64 and 66 shown in FIG. 6 may be achieved using generally square voltage, current or power pulses.

Figure 7 is a graph showing multiple heating elements showing: first, how the concentration increases stepwise when the desorption of subsequent elements is properly synchronized with the flow sample fluid velocity; The levels and gradients increase to match the expected rate of increase in the mass diffusion flux. It should be noted here that prior to the element shown in Figure 7, the analyte concentration has been amplified by a factor F by making the pulse length of the initial element F times longer than the pulse length (H1) of element 100, Or by pulsing elements 1, 2, . It will be appreciated that, due to the presence of diffusion, each concentration pulse decreases in amplitude but increases in length as it passes through the lower channel 32 . To accommodate this increased length, it is conceivable to increase the length of each successive heating element along the flow sample fluid. For example, the second heating element 102 may have a length W ₂ that is greater than the length W ₁ of the first heating element 100 . Similarly, the third heating element 104 may have a length W ₃ that is greater than the length W ₂ of the second heating element 102 . It is therefore conceivable that each heating element 100, 102 and 104 is longer in length relative to the adjacent upstream heating element, in increments corresponding to the expected increase in length of the concentration pulse of the upstream heating element due to diffusion.

To simplify control of the heating elements, the length of each successive heating element can be kept constant, resulting in the same overall heater resistance between heating elements, allowing the use of the same voltage, current or power pulses to produce similar temperature profiles. Alternatively, the heating elements can be of different lengths and the controller can provide different voltage, current or power pulse amplitudes to the heating elements to produce similar temperature profiles.

Figure 8 is a graph showing the density pulse 110 to reach the 100% density level. It can be appreciated that even if the concentration pulse 110 reaches a predetermined concentration threshold, such as 100%, the concentration of the corresponding component can still be determined. To do so, detectors 50, 128, 164 may detect concentration pulses 110 and controllers 14, 130 integrate the detector output signals over a period of time to determine the concentrations of corresponding components in raw sample stream 45.

The heating elements 20, 22, 24 and 26 may be GC film coated on the top and bottom surfaces, thereby reducing the width of the heating element surface and power consumption by approximately twofold. The manufacture of these heating elements involves two coating steps, where the second step requires wafer-wafer bonding and coating after protecting the first coating in the second wafer and dissolving the first wafer.

FIG. 9 is a schematic diagram of another exemplary sensor assembly 15 similar to that shown in FIG. 3 . The sensor assembly may include a simpler solenoid pump 120 , flow-through sample fluid 122 , concentrator 124 , separator 126 , detector 128 and controller 14 or 130 . At the request of controller 14 , 130 , solenoid pump 120 may draw sample 45 from flue gas stream 132 through one-way valve 134 . The controller 14, 130 can then cause the solenoid pump 120 to provide the flow sample fluid 45 to the concentrator 124 at the desired pressure.

Concentrator 124 may include two or more interactive elements in communication with flow sample fluid 45 . The concentrator 124 may also include two or more heating elements in thermal communication with the interactive elements. When energized, each heating element heats a corresponding interactive element, causing the interactive element to desorb selected components into the flow sample fluid. As noted above, the controller 14, 130 may energize the heating elements in phase sequence to provide enhanced concentration pulses.

Flow sample fluid 45 may carry the concentration pulse to separator 126 . Separator 126 separates selected components from the concentration pulse and provides the separated components to detectors 50,128,164. The detectors may provide signals to the controller 14, 130 indicating the concentration levels of the respective constituents. The controller 14, 130 can also determine the concentration in the raw gas sample by dividing the detected concentration level by the concentration amplification factor provided by the adsorbent material of each interactive element and the multiplier effect provided by the phased heater arrangement. The actual concentration level of each ingredient.

FIG. 10 is a schematic diagram of another exemplary sensor assembly 15 . FIG. 11 is a timing chart showing the operation of the sensor assembly 15 shown in FIG. 10 . The sensor assembly 15 may include a pump 152 , a gas preheater 154 and a microbridge integrated circuit chip 156 . The microbridge integrated circuit chip 156 includes channels 158 , 32 , a plurality of heating elements 160 a , 160 b , 160 c and 160 d , split heater 162 and detectors 164 , 128 , 50 . The individual heating elements 160a, 160b, 160c and 16Od, the separation heater 162 and the detector 164 are arranged on a support 30 which extends over the channels 158, 32 (eg Fig. 5b). Within the channels 158, 32 are provided interactive elements (not explicitly shown) which are thermally connected to the respective heating elements 160a, 160b, 160c and 16Od.

The microbridge integrated circuit chip 156 may also include a heater control block 166 and a plurality of drive transistors 168 a , 168 b , 168 c , 168 d and 170 . The heater control block 166 can individually energize each of the heating elements 160a, 160b, 160c, and 160d by energizing the corresponding energizing transistors 168a, 168b, 168c, 168d, respectively. Similarly, heater control block 166 may energize separation heater 162 by turning on transistor 170 . Heating or cooling block 169 (in FIG. 10 ) helps preheater 154 maintain an optimal average or bulk temperature for sensor assembly 15 operation.

The control block 180 of the sensor assembly directs the overall operation of the sensor assembly 15 . The sensor assembly control block 180 first determines a flow control signal 190 to the pump 152 . The flow control signal 190 is shown in FIG. 11 . In response, pump 152 draws a sample from flue gas 182 and provides the sample at the desired pressure to preheater 154 and ultimately to channels 158 , 32 . The preheater 154 provides preheating and the heater maintains the sample gas at the optimum operating element temperature, thus helping to prevent sample loss due to concentration and increasing the amount of components that accumulate in the various interactive elements.

The streaming sample fluid is passed down the channels 158, 32 for a predetermined time interval 192 until the interactive element reaches a state where adsorption of one or more components in the streaming sample fluid is substantially saturated and equilibrium is reached. Thereafter, the sensor assembly control block 180 notifies the heater control block 166 to start heating the heating elements in phase order. The heater control block 166 first provides a first heater enable signal 194 and a split heater enable signal 196 as shown in FIG. 11 . The first heater enable signal 194 turns on transistor 168 a and the split heater enable signal 196 turns on transistor 170 . Transistor 168a provides current to first heating element 160a, causing the temperature of first heating element 160a to increase. This heats the corresponding interactive element, which desorbs one or more components into the flow sample fluid in the form of a first concentration pulse. The first concentration pulse is carried downstream by the streaming sample fluid into the second heating element 160b. This process is repeated for the third, fourth and Nth elements.

The heater control block 166 then provides a second heater enable signal 198, which turns on the transistor 168b. Transistor 168b provides current to second heating element 160b, causing the temperature of second heating element 160b to increase. This heats the corresponding interactive element, which desorbs one or more components into the flow sample fluid in the form of a second concentration pulse. The heater control block 166 may time the second heater enable signal 198 such that the second concentration pulse substantially overlaps the first concentration pulse. Both the first and second concentration pulses are carried down into the third heating element 160c.

The timing of the second heater enable signal 198 relative to the first heater enable signal 194 may be established by previous calibration. However, the heater control block 166 may detect the resistance of the second heating element 160b. It will be appreciated that when the first concentration pulse reaches the second heating element 160b, the resistance of the second heating element 160b will begin to change because the first concentration pulse is typically hotter than the flow sample fluid. Once a predetermined resistance change is detected in the second heating element 160b, the heater control block 166 energizes the second heating element 160b via the transistor 168b. The remaining heater enable signals can be controlled similarly.

The heater control block 166 then provides a third heater enable signal 202, which turns on the transistor 168c. Transistor 168c provides current to third heating element 160c, causing the temperature of third heating element 160c to increase. This heats the corresponding interactive element, which desorbs one or more components into the flow sample fluid prior to the third concentration pulse. The heater control block 166 may time the third heater enable signal 200 such that the third concentration pulse substantially overlaps the first and second concentration pulses. The first, second and third substantially overlapping concentration pulses are carried downstream to the Nth heating element 16Od.

The heater control block 166 then provides the Nth heater enable signal 200, which turns on the transistor 168c. Transistor 168c provides current to Nth heating element 160d, causing the temperature of Nth heating element 160c to increase. This heats the corresponding interactive element, which desorbs one or more components into the flow sample fluid prior to the Nth concentration pulse. The heater control block 166 may time the Nth heater enable signal 202 such that the Nth concentration pulse substantially overlaps previously generated concentration pulses. The resulting concentration pulse is carried downstream to separator heater 162 . Separator heater 162 in conjunction with channel 158 separates selected components of the concentration pulse into individual constituent components. The gradual temperature increase of the separator should not be earlier than the end of the Nth pulse sent to the Nth concentrator element. Thus, pulse 196 begins after pulse 202 ends, as shown in FIG. 11 . Each constituent may comprise one or more compounds, depending on a number of factors including the sample gas provided.

Transistor 170 then energizes separation heater 162 at the beginning of pulse 196 in FIG. The remainder of the pulse 196 is achieved at this temperature. Heater 162 separates the various components into individual components as described above. The separated components are carried downstream by the flow sample fluid to the detector 164 . Detector 164 may be a thermal conductivity detector, a discharge ionization detector, or any other type of detector such as is commonly used in gas or liquid chromatography. Detector 164 may detect concentration levels of various individual constituents and provide corresponding signals to amplifier 210 . Amplifier 210 may amplify the detector output signal and provide the detector output signal to a data processing unit for analysis. The heater control block 166 may provide a detector enable signal 212 to enable the detector only when the individual constituents are present.

FIG. 12 is the basic layout of the integrated circuit including the concentrator, separator and detector of the trace gas device 15 . The integrated circuit may include vias 250 that run back and forth across the chip, as shown in FIG. 12 . A first part of the channel 250 has a detector 263 and a plurality of heating elements 252 extending on a support, such as the support 30 described above. An interactive element (not explicitly shown) is disposed in channel 250 adjacent each heating element. Although only one row of heating elements 252 is shown, it is contemplated that each channel branch 254a - h may have a row of heating elements 252 . Between 2 and 1000 heating elements may be spaced apart along channel 250 .

The second downstream portion of channel 250 has a separation heater 260 extending thereon. A separation heater may assist in separating the various components in the concentration pulse provided by heating element 252 . Finally, a detector 264 is provided downstream of the separation heater 260 on the channel 250 . A detector detects the concentration of each individual component provided by the separator.

Since the concentrator, separator and detector are set on one integrated circuit, other conventional electronic circuits can be easily integrated with it. Phased heater control block 270 and amplifier 272 can be fabricated on the same substrate. Chemical sensors, especially the introduced chemical microsensors, can offer many attractive features such as low cost, high sensitivity, robustness and small size.

While the invention has been described with respect to at least one exemplary embodiment, numerous alterations and modifications will become apparent to those skilled in the art after reading the present specification. Therefore, the meaning of the appended claims should be interpreted as broadly as possible in light of the prior art so as to include all such changes and modifications.

Claims (10)

1. A concentrator for concentrating one or more components of a fluid, comprising: two or more interactive elements (40, 42, 44, 46) spaced apart along the first channel (32) and exposed to fluid in the first channel (32), each of the interactive elements (40, 42, 44, 46) having interactive substances capable of adsorbing and desorbing selected constituents of a fluid according to the temperature of said interactive elements (40, 42, 44, 46) At least two of the include the same interactive substance; two or more interactive elements (140, 142, 144, 146) spaced apart along the second channel (31) and exposed to fluid in the second channel (31), each of the interactive The elements have an interactive substance capable of adsorbing and desorbing selected components of the fluid depending on the temperature of the interactive element, at least two of the interactive elements (140, 142, 144, 146) comprising the same interactive substance; two or more heating elements (20, 22, 24, 26), each of said heating elements interacting with a corresponding interactive element in said first channel (32) and a corresponding interactive element in said second channel (31) Type element thermal connection; and control means (14, 130), connected to said two or more heating elements (20, 22, 24, 26), allowing said first channel (31) and said second channel (32) to Two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146) are exposed to the second heating element (20, 22, 24, 26) prior to energizing the heating elements (20, 22, 24, 26) in phase sequence. Fluid down in one (32) and second (31) channels. 2. The concentrator according to claim 1, characterized in that, said two or more interactive elements (40, 42, 44, 46) include different portions of said first channel (32) exposed to at least part of the fluid and extending therealong; and The two or more interactive elements (140, 142, 144, 146) include different portions of the second channel (31 ) exposed to at least part of the fluid and extending therealong. 3. The concentrator of claim 2, wherein each of said two or more heating elements (20, 22, 24, 26) is connected to said first (32) and second ( 31) Corresponding parts in the channel are thermally connected. 4. A concentrator for concentrating one or more components of a fluid, comprising: two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146) spaced apart and exposed to fluid along a plurality of channels (32, 31), each of said interactive elements comprising interactive substances capable of adsorbing and desorbing selected constituents of a fluid according to the temperature of said interactive elements, each of said interactive elements (40, 42, 44, 46, 140, 142, 144, 146) having a length greater than the length of each interactive element located further upstream in the fluid; two or more heating elements (20, 22, 24, 26), each said heating element being thermally connected to a corresponding interactive element; and A controller (14, 130) coupled to the two or more heating elements (20, 22, 24, 26) for energizing the heating elements in a time phase sequence. 5. A sensor assembly for detecting an enhanced concentration of one or more constituents in a fluid, comprising: two or more interactive elements (40, 42, 44, 46) spaced apart along the first channel (32) and exposed to the fluid, each of said interactive elements having a temperature to adsorb and desorb selected components in the fluid interactively; two or more interactive elements (140, 142, 144, 146) spaced apart along the second channel (31) and exposed to the fluid, each of said interactive elements having a temperature to adsorb and desorb selected components in the fluid interactively; two or more heating elements (20, 22, 24, 26), each of said heating elements interacting with a corresponding interactive element in said first channel (32) and a corresponding interactive element in said second channel (31) Type element thermal connection; and a control device (14, 130), connected to said two or more heating elements (20, 22, 24, 26), allowing said two or more interactive elements in each channel (31) to energizing the heating elements (20, 22, 24, 26) prior to exposure to fluid in a time-phase sequence such that approximately when an upstream concentration pulse generated by one or more upstream interactive elements reaches the downstream interactive element , each of said interactive elements is heated and desorbs a selected component into the fluid; separation means (126) for separating selected components of one of the concentration pulses provided by the one or more interactive elements into individual constituent components; and detection means (127, 128) for detecting the concentration of one or more of said individual constituents. 6. A sensor assembly according to claim 5, characterized in that the detection means (127, 128) comprise a thermal conductivity detector. 7. A sensor assembly according to claim 5, characterized in that the control means (14, 130) is in an inactive sleep state when the heating element is not energized. 8. A method for concentrating one or more components of a fluid, the method comprising: providing a set of two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146), each set spaced along a respective one of the plurality of lanes (32, 31) open and exposed to a fluid, each of said interactive elements having an interactive substance capable of adsorbing and desorbing a selected component of a fluid according to the temperature of said interactive element, said interactive elements (40, 42, 44, 46, 140, 142, 144, 146) comprising the same interactive substance; waiting for the interactive substance to adsorb one or more components from the fluid; and Two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146) in a set are heated in phase order. 9. A method for concentrating one or more components of a fluid, the method comprising: N interactive elements (40, 42, 44, 46, 140, 142, 144, 146) are provided for each of the M channels (32, 31), wherein N and M are greater than 1, and the N Each of the interactive elements is spaced apart along each channel and exposed to the fluid, each of the N interactive elements includes an interactive element capable of adsorbing and desorbing a selected component of the fluid based on the temperature of the interactive element. such that upon heating, each of said N interactive elements desorbs a selected constituent into the fluid to produce a corresponding concentration pulse which is carried downstream by the fluid to the downstream interactive element; exposing said N interactive elements of each channel to a fluid; waiting for said N interactive substances in each of said channels to adsorb one or more components from a fluid; and The N interactive elements (40, 42, 44, 46, 140, 142, 144, 146) in each channel (32, 31) are heated in phase order such that when interacted by one or more upstream When the concentration pulse of each channel provided by the interactive element reaches the downstream interactive element, each downstream interactive element is heated. 10. A concentrator for concentrating one or more components of a fluid, comprising: a plurality of channels (32, 31), wherein each channel of the plurality of channels has two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146) along the Channels are spaced apart and exposed to the fluid, each of said interactive elements comprising an interactive substance capable of adsorbing and desorbing selected constituents of the fluid based on the temperature of said interactive element, said interactive elements (40, 42, 44, 46, 140, 142, 144, 146) are arranged in the fluid such that the sample fluid must pass through the first interactive element and then through the second interactive element; two or more heating elements (20, 22, 24, 26), each said heating element being thermally connected to a corresponding interactive element in each said channel; and a controller (14, 130), connected to said two or more heating elements, allowing said two or more interactive elements (40, 42, 44, 46, 140, 142, 144, 146) Exposure to fluid prior to energizing the heating element in a time-phase sequence.

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