JP5814761B2 - CO2 concentration baseline correction apparatus and method - Google Patents

Description

  The present invention relates to a CO2 concentration baseline correction apparatus and method for correcting a baseline of measured values of CO2 concentration using a reference value.

  Conventionally, a solid electrolytic type CO2 sensor has been used as a sensor for measuring the concentration of CO2. In this CO2 sensor, the sensor signal has a drift over time, and this drift is corrected using a reference value. This correction of the sensor signal using the reference value is called baseline correction (for example, see Patent Documents 1 and 2).

  In this baseline correction, there is a period when there is no person who periodically generates CO2 in the building, and the tendency that the CO2 concentration in the building decreases to around 400 ppm, which is the outside air concentration, due to ventilation by outside air, The minimum value of the CO2 concentration within a predetermined time (period) sampled by the CO2 sensor is used as a baseline, and this baseline is replaced with 400 ppm. 400 ppm in this case is the reference value.

JP-A-11-14591 JP-A-11-14583

  However, with the conventional baseline correction, the CO2 concentration in the building (measurement target space) may not decrease to near the outside air concentration in an environment where the airtightness of the building is high or people are resident for 24 hours. On the contrary, there is a concern that an error may be superimposed on the measured value of the CO2 concentration with the baseline corrected (hereinafter referred to as the measured value of the CO2 concentration after the baseline correction).

For example, in an environment where the minimum concentration (minimum value of CO2 concentration within a certain period (period) sampled by the CO2 sensor) is reduced to only 600 ppm, 600 ppm is set to 400 ppm (reference value) by baseline correction, An error of -200 ppm occurs in the measured value of the CO2 concentration after line correction.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a base of CO2 concentration capable of preventing an error from being superimposed on a measured value of CO2 concentration after baseline correction. It is to provide a line correction apparatus and method.

  In order to achieve such an object, the baseline correction apparatus according to the present invention includes a CO2 concentration measuring means for measuring the CO2 concentration in the measurement target space at a fixed period, and a predetermined value determined as the CO2 concentration of the outside air. Each time the CO2 concentration in the measurement target space is measured, the difference between the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration is obtained every time the CO2 concentration in the measurement object space is measured. When the difference continues within a predetermined allowable range for a predetermined time, it is determined that the measured value of the CO2 concentration is saturated by the CO2 concentration saturation determining means for determining that the measured value of the CO2 concentration is saturated and the CO2 concentration saturation determining means. Further, the present invention is characterized by comprising baseline correction means for using the measured value of CO2 concentration as a baseline and replacing the baseline with a reference value.

  According to the present invention, every time the CO2 concentration in the measurement target space is measured, the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration (for example, the moving average of 12 hours). When the difference is obtained and the difference continues within a predetermined allowable range (for example, −25 ppm to +25 ppm) for a predetermined time (for example, 12 hours), it is determined that the measured value of the CO2 concentration is saturated. Then, the measured value of the CO2 concentration determined to be saturated is replaced with a predetermined value (reference value) determined as the CO2 concentration of outside air. That is, the measured value of the CO2 concentration determined to be saturated is used as a baseline, and this baseline is replaced with a reference value (for example, 400 ppm).

  The form of EXP function (exponential function) change in which the CO2 concentration in the measurement target space decreases as it is diluted with the outside air and gradually decreases and then eventually saturates to the outside air concentration. It is known to be. Here, since there is no CO2 concentration other than outside air that is constant as it is saturated for a long period of time and lower than the concentration in the measurement target space, the change in the CO2 concentration gradually decreases and it appears to be saturated for a long period of time. This means that the saturated concentration at that time is the CO2 concentration of the outside air.

  In the present invention, every time the CO2 concentration in the measurement target space is measured, a difference between the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration is obtained, and the difference continues for a predetermined time. If the measured value of the CO2 concentration is saturated, it is considered that the concentration change gradually decreases and is saturated for a long time. The measured value of the CO2 concentration is regarded as a baseline, and this baseline is replaced with a reference value. As a result, baseline correction is not performed in an environment where the measured value of CO2 concentration does not decrease to near the outside air concentration, that is, baseline correction is performed only in an environment where the measured value of CO2 concentration decreases to near the outside air concentration. An error is prevented from being superimposed on the measured value of the CO2 concentration after the line correction.

  According to the present invention, every time the CO2 concentration in the measurement target space is measured, a difference between the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration is obtained, and the difference is determined for a predetermined time. If the measured value of the CO2 concentration is saturated when it continues to be within the allowable range, the measured value of the CO2 concentration determined to be saturated is replaced with the reference value. Therefore, it is possible to prevent the error from being superimposed on the measured value of the CO2 concentration after the base line correction by performing the base line correction only in an environment where the air concentration does not decrease to near the outside air concentration.

It is a figure showing the outline of the system using one embodiment of the baseline correction device of CO2 concentration concerning the present invention. It is a functional block diagram of the baseline correction apparatus of the CO2 concentration used in this system. It is a flowchart of the processing operation which CPU in this baseline correction apparatus performs. It is a figure which shows a state that the CO2 density | concentration in a measuring object space is diluted with external air and falls.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of a system using an embodiment of a baseline correction apparatus for CO2 concentration according to the present invention.

  In FIG. 1, reference numeral 100 denotes a measurement target space for CO2 concentration, and reference numeral 200 denotes a CO2 concentration baseline correction apparatus according to the present invention. The measurement target space 100 includes a CO2 sensor S1 as means for measuring the CO2 concentration in the space. is set up. Note that the measurement target space 100 may be a space where people are active, and is not limited to a space in a building.

  FIG. 2 shows a functional block diagram of a CO2 concentration baseline correction apparatus (hereinafter simply referred to as a baseline correction apparatus) 200. The baseline correction apparatus 200 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with the hardware, and the measurement value is a function block unique to the present embodiment. Acquisition unit 1, measured value storage unit 2, reference value storage unit 3, moving average calculation unit 4, difference calculation unit 5, saturation determination unit 6, determination time storage unit 7, and allowable range storage unit 8 and a baseline correction unit 9. In this embodiment, the CO2 sensor S1 is provided as one of the components of the baseline correction device 200.

  In the baseline correction apparatus 200, the measured value capturing unit 1 captures the measured value pvi of the CO2 concentration from the CO2 sensor S1 at a constant cycle. The measured value storage unit 2 stores the measured value pvi of the CO2 concentration from the CO2 sensor S1 taken in at regular intervals in time series. The reference value storage unit 3 stores a predetermined value determined as the CO2 concentration of outside air as a reference value. In this embodiment, a predetermined value determined as the CO2 concentration of the outside air is set to 400 ppm, and this 400 ppm is stored in the reference value storage unit 3 as a reference value.

  Each time the measured value pvi of the CO2 concentration from the CO2 sensor S1 is input, the moving average calculator 4 measures the measured value of the CO2 concentration for the past 12 hours including the input measured value pvi of the CO2 concentration. The average of the measured values of the CO2 concentration for 12 hours is read as the moving average value pvimav of the measured value pvi.

  Each time the measured value pvi of the CO2 concentration from the CO2 sensor S1 is input, the difference calculating unit 5 sets the input measured value pvi of the CO2 concentration as the current value, and calculates the current value pvi of the CO2 concentration and the moving average calculation. The difference Δpvi (Δpvi = pvimav−pvi) between the CO2 concentration calculated by the unit 4 and the moving average value pvimav is obtained and output as the difference Δpvi between the current value and the moving average value.

  The saturation determination unit 6 receives the difference Δpvi from the difference calculation unit 5 one after another, and when this difference Δpvi continues for a predetermined time T and continues within a predetermined allowable range ± α, the measured value of the CO2 concentration is Judged saturated. The determination time storage unit 7 stores a predetermined time T used by the saturation determination unit 6, and in this embodiment, T = 12 hours. The permissible range storage unit 8 stores a permissible range ± α used by the saturation determination unit 6, and in this embodiment, α = 25 ppm.

  The baseline correction unit 9 receives the determination result as to whether or not the measured value of the CO2 concentration from the saturation determining unit 6 is saturated. If it is determined that the measured value of the CO2 concentration is saturated, the CO2 sensor S1 at that time The measured value pvi of the CO2 concentration from is used as a baseline, and this baseline is replaced with a reference value (400 ppm) stored in the reference value storage unit 3. Then, the measurement value pvi of the CO2 concentration in which the baseline is replaced with the reference value, that is, the measurement value pvi of the CO2 concentration with the baseline corrected is output as the measurement value pvi ′ of the CO2 concentration after the baseline correction. .

  In the functional block diagram shown in FIG. 2, the CO2 sensor S1 and the measured value capturing unit 1 constitute a CO2 concentration measuring unit in the present invention, and the moving average calculating unit 4, the difference calculating unit 5, and the saturation determination The unit 6 constitutes CO2 concentration saturation determination means. The reference value storage unit 3 corresponds to a reference value storage unit, and the baseline correction unit 9 corresponds to a baseline correction unit. Further, the functions of the measurement value capturing unit 1, the moving average calculation unit 4, the difference calculation unit 5, the saturation determination unit 6, and the baseline correction unit 9 are realized as processing functions of the CPU 10 according to a program.

  FIG. 3 shows a flowchart of processing operations executed by the CPU 10 in the baseline correction apparatus 200. The CPU 10 captures the measured value pvi of the CO2 concentration from the CO2 sensor S1 (step S101), and stores the captured measured value pvi of the CO2 concentration in the measured value storage unit 2 (step S102).

  Then, the measured value of the CO2 concentration for the past 12 hours including the captured measured value pvi of the CO2 concentration is read from the measured value storage unit 2, and the average of the measured values of the CO2 concentration for 12 hours is the moving average of the measured value pvi. A value pvimav is calculated (step S103).

  Next, the CPU 10 sets the measured value pvi of the CO2 concentration taken in step S101 as a current value, and the difference Δpvi (Δpvi = pvimav) between the current value pvi of this CO2 concentration and the moving average value pvimav of the CO2 concentration calculated in step S103. -Pvi) is obtained as a difference between the current value and the moving average value (step S104).

  Then, it is confirmed whether or not the obtained difference Δpvi is within the allowable range ± α stored in the allowable range storage unit 8, that is, whether it is within the allowable range of −25 ppm to +25 ppm (step S105). ). If it is not within the allowable range ± α (NO in step S105), the time value TX of the soft timer is set to 0 (step S106), the process returns to step S101, and the measurement value pvi of the CO2 concentration is repeatedly taken. . Note that the time value TX of the soft timer is set to 0 in the initial state.

  On the other hand, if the difference Δpvi falls within the allowable range ± α (YES in step S105), the timing operation of the soft timer is started (step S108), the process returns to step S101, and the measurement value pvi of CO2 concentration is repeatedly taken. . Thereby, the difference Δpvi is obtained one after another in the same manner as described above.

  In this case, if the timing operation of the soft timer has been started (NO in step S107), the timing operation is continued as it is, and the measurement value pvi of CO2 concentration is repeatedly taken in. If the difference Δpvi is outside the allowable range ± α (NO in step S105), the timing operation of the soft timer is stopped and the measured value TX is returned to 0 (step S106), and the measured value pvi of the CO2 concentration is captured. repeat.

  Here, the difference Δpvi continues to be within the allowable range ± α (YES in step S105), and when the time value TX of the soft timer becomes equal to or greater than the predetermined time T stored in the determination time storage unit 7 (YES in step S109). The CPU 10 replaces the measured value pvi of the CO2 concentration at that time with the reference value (400 ppm) stored in the reference value storage unit 3 (step S110). That is, the baseline of the measured value of the CO2 concentration is corrected.

  FIG. 4 shows how the CO2 concentration in the measurement target space 100 decreases as it is diluted with outside air. The vertical axis shown in FIG. 4 is the CO2 concentration, and the horizontal axis is time. As shown in this figure, when the CO2 concentration in the measurement target space 10 is decreased by being diluted by the outside air, the CO2 concentration is gradually decreased, and finally the EXP is saturated to the outside air concentration. It is known that the function (exponential function) changes. Here, since there is no CO2 concentration other than outside air that is constant as it is saturated for a long period of time and is lower than the concentration of the measurement target space 10, the change in CO2 concentration gradually decreases and is saturated for a long period of time. Presenting means that the saturation concentration at that time is the CO2 concentration of the outside air.

  In the present embodiment, every time the CO2 concentration in the measurement target space 100 is measured, a difference Δpvi between the measured value pvi of the measured CO2 concentration and the moving average value pvimav of the measured CO2 concentration is obtained. When the difference Δpvi continues to enter the allowable range ± α (−25 ppm to +25 ppm) for a predetermined time T (12 hours), the concentration change gradually decreases by determining that the measured value pvi of the CO2 concentration is saturated. Therefore, it is considered that the state is saturated for a long time, and the measured value pvi of the CO2 concentration at that time is replaced with a reference value (400 ppm). As a result, baseline correction is not performed in an environment where the measured value of CO2 concentration does not decrease to near the outside air concentration, that is, baseline correction is performed only in an environment where the measured value of CO2 concentration decreases to near the outside air concentration. It is possible to prevent the error from being superimposed on the measured value pvi ′ of the CO2 concentration after the line correction.

  In the embodiment described above, it is confirmed whether or not the difference Δpvi (Δpvi = pvimav−pvi) between the current value pvi of the CO2 concentration and the moving average value pvimav is within the allowable range ± α. The absolute value (| Δpvi |) of the difference Δpvi between the current density value pvi and the moving average value pvimav may be obtained as a difference, and it may be confirmed whether or not the difference | Δpvi | .

  In the above-described embodiment, the baseline correction device 200 is provided separately from the CO2 sensor S1, but the function of the baseline correction device 200 may be incorporated into the CO2 sensor S1.

  In the above-described embodiment, the predetermined time T is 12 hours, but the predetermined time T is not limited to 12 hours. For example, if the time zone in which the measurement target space 100 is unattended is 10 hours of 22:00 to 8:00 in the 24 hours a day, the baseline is corrected every day if the predetermined time is 5 hours. Will be done automatically.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment, but the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS S1 ... CO2 sensor, 1 ... Measurement value acquisition part, 2 ... Measurement value storage part, 3 ... Reference value storage part, 4 ... Moving average calculation part, 5 ... Difference calculation part, 6 ... Saturation judgment part, 7 ... Judgment time Storage unit, 8 ... Allowable range storage unit, 9 ... Baseline correction unit, 10 ... CPU, 100 ... Measurement object space, 200 ... Baseline correction device.

Claims (2)

CO2 concentration measuring means for measuring the CO2 concentration in the measurement target space at regular intervals;
Reference value storage means for storing a predetermined value determined as the CO2 concentration of outside air as a reference value;
Each time the CO2 concentration in the measurement object space is measured, a difference between the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration is obtained, and the difference is determined in advance for a predetermined time. CO2 concentration saturation determining means for determining that the measured value of the CO2 concentration is saturated if it continues to fall within the allowable range,
A baseline of CO2 concentration, comprising: a measured value of the CO2 concentration determined to be saturated by the CO2 concentration saturation determination means as a baseline, and a baseline correction means for replacing the baseline with the reference value Correction device. A CO2 concentration measurement step for measuring the CO2 concentration in the measurement target space at regular intervals;
A reference value storing step for storing a predetermined value determined as the CO2 concentration of outside air as a reference value;
Each time the CO2 concentration in the measurement object space is measured, a difference between the measured value of the measured CO2 concentration and the moving average value of the measured CO2 concentration is obtained, and the difference is determined in advance for a predetermined time. A CO2 concentration saturation determination step for determining that the measured value of the CO2 concentration is saturated if it continues to fall within the allowable range;
And a baseline correction step of replacing the baseline with the measured value of the CO2 concentration determined to be saturated by the CO2 concentration saturation determining step, and replacing the baseline with the reference value. Correction method.

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