Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
  • G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content

Definitions

• the present invention relates to a method for improving the signal-to-noise ratio (hereinafter also referred to as SN ratio) of a sensor output signal, and in particular, when performing a type of measurement in which a reference fluid and a sample fluid are periodically switched.
• the present invention relates to a method and apparatus for improving the signal-to-noise ratio of an output signal from a computer.
• One of the major issues when measuring minute quantities is how to suppress noise. For example, but not limited to this, if we try to realize a function corresponding to the human sense of smell using a measurement system, the human sense of smell can detect very dilute gases, depending on the target substance. . However, even if we try to achieve the same sensitivity to such gases as humans, it is often impossible to obtain a sensor with high sensitivity. Therefore, it is required to further increase the sensitivity of the sensor, which is usually quite difficult. Even if a sensor with high sensitivity is obtained, it is often required to detect components at even lower concentrations. Furthermore, in many actual measurements, it is necessary to detect many types of substances, so it is often insufficient to simply develop a sensor that exhibits high sensitivity to a small number of specific substances. Therefore, it would be very beneficial if a method for improving the SN ratio could be provided that can be uniformly applied to many sensors.
• An object of the present invention is to provide a method for improving the S/N ratio of a sensor output signal obtained by periodically switching between a reference fluid and a sample fluid and applying the same to a sensor.
• a method for improving the signal-to-noise ratio of a sensor output signal obtained from the sensor by periodically switching between a reference fluid and a sample fluid and applying the same to the sensor A method is provided for improving the signal-to-noise ratio of a sensor output signal by integrating a period-by-period time-varying signal over multiple periods.
• the integration over the plurality of periods may be performed for the entire time period of each period or a partial time period that is a part of the time period.
• the senor has a sensitive membrane capable of adsorbing and/or absorbing and desorbing at least some components in the sample fluid or the reference fluid, and the sensitive membrane has characteristics due to the adsorption and/or absorption and desorption. It may be possible to detect changes in Further, the sensor may be a surface stress sensor that detects a change in surface stress caused on the sensor by a change in the characteristics of the sensitive film. Further, the length of the switching period for periodically switching between the reference fluid and the sample fluid is the length of each small section obtained by dividing a given time section into a plurality of small sections of equal length. good.
• the integration of the time-varying signal for each cycle within the time T ⁇ N is The signal-to-noise ratio of the resulting signal is T ⁇ N/T, which is the time-varying signal obtained from the sensor by periodically switching between the reference fluid and the sample fluid for a time T' greater than T.
• T ⁇ N/T is the time-varying signal obtained from the sensor by periodically switching between the reference fluid and the sample fluid for a time T' shorter than T.
• the ratio of the noise component to the signal component in the output signal can be reduced without extremely lengthening the measurement time. value can be reduced.
• FIG. 1 is a diagram schematically showing a configuration example of a measuring device that can be used in the present invention.
• FIG. 7 is a diagram schematically showing another configuration example of a measuring device that can be used in the present invention.
• FIG. 3 is a diagram illustrating that a noise signal is superimposed on an actual output signal. To explain the difference in signal-to-noise ratio between measuring one period and measuring multiple periods within a given time range for an output signal whose true output signal varies according to a linear function of time. illustration.
• FIG. 3 is a diagram illustrating an example of an output signal in which the true output signal varies according to a step function of time.
• FIG. 4 is a diagram illustrating an example of an output signal in which the true output signal varies according to an exponential function of time.
• FIG. 7 is a diagram showing that when switching between a reference fluid and a sample fluid is repeated, the level of the output signal at the time of switching changes each time.
• FIG. 3 is a diagram schematically showing how an output signal asymptotically approaches a constant value as time passes from switching between a reference fluid and a sample fluid.
• the output signal at the time of switching is V o , and a diagram schematically showing how the output signal V(t) asymptotically approaches the saturated output value V sat by continuing to flow the sample fluid from this point.
• the output signal at the time of switching is V o , and a diagram schematically showing how the output signal V(t) asymptotically approaches the baseline by continuing to flow the reference fluid from this point.
• the vertical axis shows the SN ratio improvement index F(N)/ ⁇ N, which is the effect of improving the SN ratio by integrating N times, and the horizontal axis shows T/ ⁇ 0 (where ⁇ 0 is the time constant of the sensor response).
• This is a graph taken.
• FIG. 3 is a diagram showing a graph of the results of the method of the present invention performed using the measuring device configured as shown in FIG. 2; 14 is a diagram showing a graph obtained by adjusting the time axis of each graph shown in FIG. 13 so that one measurement period is approximately the same as the length in the width direction of the plot area of the graph.
• 2 is a graph of the SN ratio improvement index F(N) when the parameter ⁇ / ⁇ 0 is set to 20, which is the value in the example.
• the sample fluid can be identified by performing various analyzes on the sensor output signal obtained by periodically switching between the reference fluid (also called purge fluid (or purge gas in the case of gas)) and sample fluid. , composition determination, component quantification, etc.
• FIG. 1 is a diagram conceptually showing an example of the configuration of a device that performs such measurements. Although the configuration of the apparatus is shown here when the fluid is gas, the configuration is basically the same even when the fluid is liquid. Note that Non-Patent Document 1 includes a brief description to the effect that sensor signals that change on the time axis are averaged 25 times. However, there is no description of how sensor signals obtained through specific measurement sequences are averaged.
• a reference fluid (reference gas) is supplied to two mass flow controllers (MFC) from the left side of the figure.
• the reference gas passing through the upper MFC is sent to the upper gas flow path at a set flow rate.
• the reference gas passing through the lower MFC is also sent to the lower gas flow path at a set flow rate.
• an upstream vial containing a sample is provided in the middle.
• the reference gas passes through the vial it mixes with the sample vapor to form a sample fluid (sample gas).
• the reference gas and sample gas sent through the two gas flow paths are mixed in a vial on the downstream side, and then sent to a sensor module housing a sensor (not shown).
• the two MFCs periodically perform gas delivery/stop operations in opposite phases. That is, the upper MFC allows the gas to flow at a set flow rate while the lower MFC stops the gas flow for a first period of time, and conversely, the upper MFC stops the gas flow while the lower MFC
• the second time interval in which the side MFC flows the gas at the set flow rate is repeated alternately. This makes it possible to implement the operation of periodically switching between the reference fluid and the sample fluid as described above and supplying them to the sensor housed in the sensor module. The output of this sensor is given to the information processing device, where various necessary processing/calculations, transfer to the higher-level device, etc. are performed.
• the information processing device controls the operation of various elements within the MFC and other measuring devices, controls the man-machine interface of the measuring device, sends and receives control information, etc. to and from the higher-level device, and performs various other operations.
• the present invention does not limit the operating principle of the sensor to a specific one.
• sensors that can be used include: surface stress, stress, force, surface tension, pressure, mass, elasticity, Young's modulus, Poisson's ratio, resonant frequency, frequency, volume, thickness, viscosity, Density, magnetic force, magnetic quantity, magnetic field, magnetic flux, magnetic flux density, electrical resistance, electrical quantity, permittivity, power, electric field, charge, current, voltage, potential, mobility, electrostatic energy, capacitance, inductance, reactance, susceptance,
• a type of sensor may be used that detects a physical parameter or a combination of physical parameters selected from admittance, impedance, conductance, plasmon, refractive index, luminous intensity, and various other physical parameters.
• MSS membrane-type surface stress sensor
• the sample is a volatile liquid, which is stored in a vial on the upstream side of the lower flow path.
• the sample When the sample is given as a solid containing volatile components, the solid may be stored as is in a vial on the upstream side, and the sample gas may be obtained by flowing the reference gas from the upstream side.
• the sample gas By storing a solid sample dissolved in a solvent in an upstream vial, it can be handled in the same way as a liquid sample.
• the sample is given in the form of a gas (sample gas) from the beginning, instead of using the configuration shown in Figure 1, it is possible to directly supply the sample gas to the lower MFC and use an upstream vial. It is possible to have a configuration in which this is not the case.
• a valve mechanism that selects one of two inlets connected to two gas flow paths and connects it to an outlet, and a sensor module is provided through this valve mechanism.
• a pump may be provided to control the flow rate of the reference gas/sample gas fed into the system. Note that this pump can be installed at any position on the gas flow path, but if it is installed downstream of the valve mechanism (between the valve mechanism and the sensor module, or on the exhaust side of the sensor module), one pump can provide the standard Both fluid and sample fluid can be controlled.
• the reference fluid it is customary to use a fluid that contains only components that are not normally measured, and when the fluid is a gas, in many cases, air or nitrogen gas is used as the reference fluid ( Measurements are made using the reference gas).
• a general-purpose fluid must be used as the reference fluid, and any fluid can be used as the reference fluid as long as it does not adversely affect the measurement.
• FIG. 2 shows an example of the configuration of a measuring device that can use any fluid as a reference fluid in this way.
• gas is assumed to be used as the reference fluid and the sample fluid.
• the lower flow path for supplying the sample gas is the same as the configuration shown in FIG. 1.
• a vial bottle for further adding a reference sample to the reference gas supplied from the upstream side is provided in the upper channel for supplying the reference gas. Therefore, a new reference gas (for example, nitrogen gas or air) to which the components of the reference sample are added is supplied to the sensor module. Therefore, the output signal from the sensor module will reflect the difference between the new reference gas and the sample gas.
• a new reference gas for example, nitrogen gas or air
• a vial bottle is not essential for producing a new reference gas; for example, if the reference sample is gaseous from the beginning or is highly vaporizable.
• a parallel reference sample introduction device may be used, such as blowing a reference sample gas in parallel into the flow path of the reference gas coming from the upstream side.
• a reference gas containing a reference sample component may be supplied to the reference gas supply route from the beginning.
• reference gas refers to the gas given to the entrance of the flow path on the reference gas side and the gas exiting from the flow path on the reference gas side.
• the gas given to the entrance of each flow path is usually odorless, such as nitrogen or air, and is a gas consisting only of components that are not normally the target of detection. Please note that it is sometimes referred to by the name "inert gas”, which is derived from a certain thing.
• inert gas which is derived from a certain thing.
• the reference gas and sample gas referred to here are more generally referred to as a reference fluid and a sample fluid, respectively, but they will be represented by "gas”.
• gas may be used as a representative of "fluid,” but such explanations naturally apply to fluids other than gas, unless it is clearly unreasonable.
• a certain composition amount of each component and/or type of components contained
• a fluid having the reference composition can be provided as the reference fluid.
• the exact amount of such uninteresting components i.e., the magnitude of the signal component contributed by the uninteresting components in the sensor output signal
• the change in the sensor output signal corresponding to that component is within a somewhat narrow range, it is possible to increase the dynamic range of the sensor output signal by appropriately setting the amount of the component of no interest in the reference fluid. and noise can be reduced.
• actual sensor output signals include not only signals under ideal conditions (true output signals) but also random noise signals based on various factors. If the sensor sensitivity to the components in the sample fluid is sufficiently high and the components are contained in the sample fluid at a sufficient concentration, the true output signal will be sufficiently large compared to the noise signal, making it easy to perform visual inspection or various types of signal analysis. Sensor output signals can be evaluated with high accuracy using this method. However, in reality, the concentration of components in the sample fluid is often close to the detection limit of the sensor used, and in such cases, a large amount of noise signal is superimposed on the true output signal in the sensor output signal. However, it is not uncommon for the level of the noise signal to be higher than the true output signal.
• the signal-to-noise ratio (SN ratio) of a signal can be improved by integrating a signal in which a random noise signal is superimposed on a periodic true signal over multiple periods.
• the measurement time for a single cycle is multiplied by the number of cycles for the above integration, so this method is not suitable for applications that require measurement in a short time.
• Such an integration method cannot be applied.
• this type of integration method assumes the constancy of the measurement target and measurement device during the entire measurement period, but in reality this assumption does not hold true. I often don't.
• Non-Patent Document 4 provides a theoretical analysis of the mode of gas adsorption/desorption in a nanomechanical sensor, which is the type of sensor to which the MSS used in the embodiment of the present application belongs, and the sensor response brought about by this. Please refer to it as necessary.
• Non-Patent Document 5 analyzes the sensor response when a reference fluid and a sample fluid are periodically switched and applied to the sensor, taking into account the viscoelastic characteristics of the sensor sensitive area, so please refer to it as appropriate. sea bream. Therefore, when performing this type of measurement, it is not possible to apply a method that simply integrates the results of multiple measurements, as is done in spectroscopic analysis.
• Non-Patent Document 1 An additional comment regarding Non-Patent Document 1 is that the sensor used there (photoacoustic spectroscopic gas sensor) does not adsorb the sample on the sensor as described above due to its operating principle. It is almost negligible and the past measurement history has no real effect on the signal obtained from the current measurement. Therefore, Non-Patent Document 1 does not provide any motivation for considering how to deal with the problems in simple integration described above. From another point of view, for example, if you continue to use a measuring device, it is impossible to completely suppress fluctuations in the responsiveness of the sensor itself, such as its sensitivity, or in the characteristics of the electric circuit that inputs and amplifies minute signals from the sensor. Can not. Furthermore, various parameters such as the component composition and temperature of the sample to be measured naturally vary. Furthermore, in cases where the amount of sample that can be used is extremely small, or when it is desired to analyze a sample obtained at a certain point in time from a system that can vary over time, it is not possible to perform long-term measurements.
• the present invention takes advantage of the fact that the switching period (also called measurement period) when periodically switching the reference fluid and sample fluid and applying them to the sensor to perform one cycle of measurement can be freely set within a considerable range.
• the inventor of the present application has realized that when performing integration, instead of fixing the switching period length and repeating the measurement unit of such a fixed period multiple times, the switching period can be changed.
• the switching period can be changed.
• the measurement cycle length is determined so that a desired number of cycle measurements are completed within a predetermined measurement period, and the measurement results of multiple cycles obtained in this way are integrated.
• the S/N ratio may worsen due to integration, but the true output signal may be buried in the noise signal and what shape the true output signal becomes.
• a noise reduction method is provided that can be applied when the noise signal is still desired to be further reduced.
• adsorption will be simply used to include selective adsorption of various components by the sensitive membrane, selective absorption, and the effects of both.
• the adsorption rate at a certain point is the concentration of the component near the interface on the fluid side of the fluid-sensitive membrane interface and the concentration near the interface on the sensitive membrane side. It can be thought that it is determined by the difference between the component concentration and the component concentration at . Especially in a narrow concentration range, the adsorption rate can be considered to be proportional to the concentration difference, and when the change in adsorption amount is within a narrow range, the component concentration in the sensitive membrane and the sensor output signal can be considered to be proportional.
• the concentration distribution in the sensitive film may be assumed to be uniform.
• the fluid applied to the sensor is naturally not stationary, but flows at a certain speed, and in most cases the adsorption rate by the sensitive membrane can be considered not to be very large. Even in a situation where components in the fluid are adsorbed by the membrane, the concentration of the components in the fluid applied to the sensor can be considered to be generally constant regardless of location.
• V T ( t) When the above conditions are met, the true sensor output signal V T ( t) can be expressed as V sat (1-e ⁇ (-t/ ⁇ 0 )) by solving a first-order linear differential equation.
• V sat is a constant that indicates the saturation value of the output signal V T (t) after a sufficient period of time has passed
• ⁇ 0 is a constant that indicates the saturation value of the output signal V T (t) after a sufficient period of time has passed
• ⁇ 0 is the type, temperature, flow rate, etc. of the substance in the fluid, and the type and concentration of components in the fluid.
• it is a constant determined by the characteristics of the sensitive film, etc., and is also called a time constant.
• V T (t) an actually observed output signal (a signal in which a noise signal n(t) is superimposed on a true output signal) is represented by V(t).
• FIG. 4(a) shows a case where this cycle is performed only once.
• FIG. 4(b) shows a case where N cycles of measurement are performed within the same measurement time interval (time length 2 ⁇ ).
• the maximum value S of the true signal is a ⁇ /N becomes. In other words, as the number of cycles increases, the value of S decreases in proportion to the time of one cycle. Further, by performing the integration, the noise level within the same time period divided into N periods becomes ⁇ / ⁇ (N). From this, the SN ratio of the output signal that is measured and integrated over the N periods is a ⁇ /( ⁇ (N) ⁇ ).
• the fixed measurement time interval is divided into multiple sections for measurement and integration. It can be seen that the S/N ratio is actually worse than when such division is not performed.
• FIG. 6(a) is a diagram illustrating the result of measuring only one period during a fixed measurement time interval 2 ⁇ , that is, the case where the output signal in FIG. 4(a) is changed to that shown in FIG. 5. It is.
• FIG. 6(b) switching between the sample fluid and the reference fluid is performed for N cycles during the same measurement time interval 2 ⁇ (one cycle switching means switching from the sample fluid to the reference fluid).
• one cycle switching means switching from the sample fluid to the reference fluid.
• Figure 3 shows the case where N cycles were measured.
• the true output signal V T (t) has a pattern with almost the same shape as the step function, and the difference between the reference fluid and the sample fluid is Since its maximum value V 0 is reached immediately after switching, the maximum value of the true output signal V T (t) within each period is independent of the number of periods (the number of divisions of the fixed measurement time interval) N V sat . In the end, the maximum value of the true output signal V T (t) in one cycle shortened by division is the time (2 ⁇ /N) of one cycle as a result of division, in other words, the number of divisions N becomes irrelevant. On the other hand, since the noise level due to integration is ⁇ / ⁇ (N) as in the case discussed in FIG.
• the SN ratio in this case is ⁇ (N)V sat / ⁇ . That is, even if the length of the measurement time interval is fixed to 2 ⁇ , by dividing this interval into a plurality of N intervals, switching between the sample fluid and the reference fluid in each interval, and integrating these results, It can be seen that the SN ratio is improved by ⁇ (N) times.
• the SN ratio when measuring and integrating the measurement time interval of length 2 ⁇ is divided into N parts is calculated based on the adsorption model of the sensitive membrane, which is more realistic than the example mentioned above.
• the sensor used in Non-Patent Document 1 photoacoustic spectroscopic gas sensor
• Non-Patent Document 1 Even if the sensor of Non-Patent Document 1 is adopted in a measurement system that periodically switches between the sample fluid and the reference fluid, the response signal will have a pattern intermediate between that of FIGS. 5 and 3, as discussed below. There is no need for any discussion in this case.
• the output signal V(t) which is the noise signal superimposed on the true output signal V T (t) has a pattern as shown in FIG. 7 (however, Only the patterns before and after switching from reference fluid to sample fluid are shown).
• FIG. 7 shows the pattern shown in FIG. 7
• the pattern shown in FIG. 5 shows the pattern shown in FIG. 5, which is a pattern close to a step function.
• V T (t) in the form of a first-order polynomial in FIG.
• V T (t) of a pattern close to the step function in FIG. is: (iii) ⁇ 0 ⁇ 1, ie, the time constant is very small (fast response), or (iv) T ⁇ ⁇ , ie, the measurement time for each period is very long.
• the integration is performed as many times as possible.
• ⁇ 0 is often unknown here, and in that case, for example, you can set the initial value of the time of one cycle in advance, or prepare multiple initial values, and use this. It is necessary to take measures such as switching and performing integration processing.
• the noise signal when the noise signal is relatively small and ⁇ 0 can be estimated with sufficient accuracy from the output signal pattern before integration processing, or as described above. Although ⁇ 0 is unknown, as a result of trial-and-error integration using a preset period of time, the S/N ratio was improved to some extent and the true output signal pattern became visible. If ⁇ 0 is known by etc.: In this case, the noise can be further reduced by finding an appropriate time for one cycle based on the estimated ⁇ 0 and performing measurement and integration multiple times.
• V 0 is the value of the output signal when switching the fluid
• V sat is the value of the output signal when the sample fluid is introduced for a sufficient time
• t is the elapsed time from the time of fluid switching.
• the output signal values V(t) at the time of introducing the sample fluid and the time of introducing the reference fluid described above are shown in FIGS. 9(a) and 9(b), respectively.
• sample fluid introduction phase sample fluid introduction phase
• reference fluid introduction phase reference fluid introduction phase
• V n (t) and V s,n are described in the form of recurrence formulas as shown in the above formula, but V s,n can be written as the following general solution.
• the response width of the sensor obtained during the sample fluid introduction phase (the nth introduction phase) (the amount of change in the sensor output signal during the introduction phase) ⁇ V s,n is , It can be expressed as.
• the introduction phase is repeated a sufficient number of times, that is, when n ⁇ , the above equation becomes becomes. If measurement is performed N times in this state and the sensor output signals are integrated, the noise level will be ⁇ / ⁇ (N), so the SN ratio in this case is: becomes.
• FIG. 11 is a graph in which F(N)/ ⁇ N is plotted on the vertical axis and T/ ⁇ 0 is plotted on the horizontal axis. From FIG. 11, it can be seen that the larger the length T of the sample fluid introduction phase and the reference fluid introduction phase compared to the time constant ⁇ 0 of the sensor response, the higher the integration effect.
• FIG. 12 shows the SN ratio improvement index F(N) plotted as a function of N using ⁇ / ⁇ 0 as a parameter. According to the definition of the SN ratio improvement index F(N), when F(N)>1, there is an effect of improving the SN ratio through integration. From FIG.
• an initial measurement period of 10 seconds (sample fluid introduction phase of 5 seconds, reference fluid introduction phase of 5 seconds) is compared to a period of 0.2 seconds (sample fluid introduction phase of 5 seconds).
• the measurement period is divided into 50 measurement periods each having a fluid introduction phase of 0.1 seconds and a reference fluid introduction phase of 0.1 seconds.
• N 50.
• the repeated measurements for this example if the initial measurement cycle of 10 seconds is repeated 2000 cycles, and the first 300 cycles are discarded, the remaining 1700 cycles, that is, 1700 x 10 seconds. It was found that the measurement system and the measurement target had sufficient constancy for 17,000 seconds.
• N includes a decimal part (that is, x defined as 1/N is divided into an integer part) 1)
• a noise reduction effect can be obtained.
• N instead of dividing one period (10 seconds) into 50, it can be divided into another number with a decimal point, for example, 50.1.
• 50 division cycles will be included in this time interval, and a remainder of 10-10/50.1 x 50 ⁇ 0.01996 seconds will appear. .
• This remaining time is not used during integration, but even if such remaining time exists, it is possible to improve the signal-to-noise ratio compared to using an integer number of divisions. If it is more advantageous to do so, it is of course possible to adopt a division number with a decimal part.
• the present invention can also be applied to cases other than this, for example, when the true output signal can be expressed in the form of a sum of a plurality of exponential functions having mutually different time constants.
• the above-described period division, measurement, and integration can be performed by focusing on the exponential function with the largest time constant.
• the true output signal can be expressed as a sum of a number of exponential functions having different time constants, the exponential function with a small coefficient can be ignored.
• the output signal observed while the sample fluid is flowing does not increase almost monotonically, but overshoots; that is, the output signal increases when the sample fluid starts flowing, but as the sample fluid continues to flow. It is also known that the output signal may start to decrease midway through the process. In such a case, theoretically, the sample fluid can be continued to flow from the time the sample fluid starts flowing until the point when the output signal reaches its maximum value (maximum value point), and at this point, the sample fluid can be switched to the reference fluid. can be observed without losing the information contained in the sensor response. Therefore, in the period division described so far, it is required that the division period is not shorter than the time period from when the sample fluid starts flowing to the time of the maximum value.
• the components in the sample fluid are often known to some extent in advance, rather than having no idea what the true output signal will be.
• the components of a sample fluid are known in advance based on its source, but the amount or composition ratio of multiple components is unknown.
• the sample fluid is selected from a finite number of components.
• the set of exponential function time constants that appear in the output signal corresponding to those components is also known. .
• a membrane-type surface stress sensor which is a type of surface stress sensor and was invented by the inventors of the present application, will be used as a sensor, and the measuring device configuration as illustrated in FIG. 2 will be used as a measuring device configuration.
• the reference fluid used and supplied to the sensor is not a fluid that is often considered a reference, such as nitrogen gas or air, but rather a gas containing gases originating from the same type of material as the sample being measured. Experimental results when supplied are shown. However, it is clear that this is without loss of generality.
• an experiment was conducted using the configuration shown in FIG. 2 among the two types of measurement device configuration examples listed above.
• two types of chocolate also referred to as sample chocolate and reference chocolate, respectively
• sample chocolate and reference chocolate are placed in vials in a flow path on the sample gas side and in a flow path on the reference gas side, respectively.
• nitrogen gas as an inert gas from the entrance of the channel
• the difference (deviation) in the odor of the sample chocolate from the odor of the reference chocolate was measured.
• the sensor module used the MSS as described above, and the output signal from the MSS was given to the information processing device for analysis.
• the information processing device was configured to control the gas supply and other aspects of the entire measuring device by controlling the MFC or other components not shown. With such a configuration, an experiment was conducted to reduce noise by integrating sensor output signals according to the present invention.
• the time-varying pattern of the output signal from the sensor module also differs from that of the reference gas.
• the output signal is usually much smaller than the output signal when the gas supplied from the flow path to the sensor module does not contain the odor generated from the reference chocolate (for example, when using the configuration shown in Figure 1). It tends to be.
• This example shows that even a slight difference in odor between two types of samples belonging to the same class of "chocolate" can be detected as a distinct pattern in the output signal from the sensor.
• the measurement time interval 2 ⁇ mentioned above was set to 120 seconds.
• the measurement was performed by setting the sample gas and reference gas supply times to the sensor to 0.1 seconds, 0.3 seconds, 1.0 seconds, 3.0 seconds, and 5.0 seconds.
• the number of divisions N is 600, 200, 60, 20, and 12, respectively.
• the upper graph is the raw output signal without integration (specifically, the output signal during the final measurement of the measurements repeated by the corresponding number of divisions)
• the lower graph shows the result of integrating the output signals as many times as the corresponding number of divisions, as described above.
• Figures 13 and 14 are graphs of the same data, but in Figure 13 the x-axis (that is, the time axis) is fixed, whereas in Figure 14, the x-axis (that is, the time axis) is fixed, whereas in Figure 14, the The time axis of each graph is adjusted so that the signal pattern of one cycle represented by one supply of reference gas fills the entire width of the graph. Note that in each graph in FIGS. 13 and 14, the vertical axis (output signal value) is fixed.
• the S/N ratio is improved in the integration result and a signal pattern closer to the true output signal is obtained. can.
• the SN of measurement results can be improved without increasing the overall time available for measurement.
• the ratio can be improved.

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