JP5629169B2 - Gas alarm and control method thereof - Google Patents

Description

  The present invention relates to a gas alarm and a control method thereof.

  2. Description of the Related Art Conventionally, smoke-type fire alarms that detect and alarm smoke generated during a fire have been proposed. In the inspection work of the smoke type fire alarm, the inspector carries a spray can containing chlorofluorocarbon and sprays chlorofluorocarbon on the fire alarm. As a result, the inspector creates a simulated fire condition. And the inspector performs the inspection by determining whether or not the alarm is normally given in the pseudo fire condition.

  On the other hand, a gas alarm device having a catalytic combustion type gas sensor has been proposed. This alarm device has a heater. When the gas leaks, the gas is burned by the heater, and the temperature of the heater rises due to the combustion. As a result, when the gas leaks, the resistance value of the heater changes, and the output from the catalytic combustion type gas sensor also changes. The gas alarm device is configured to detect a gas leak by detecting this output change and perform an alarm (see, for example, Patent Document 1).

JP 2003-085674 A

  Conventionally, however, Freon gas has been sprayed on the gas alarm device due to an error of an inspector. In such a case, the chlorofluorocarbon gas is burned and carbonized by the catalytic combustion type gas sensor and adheres to the surface of the catalytic combustion type gas sensor. As a result, the characteristics of the catalytic combustion type gas sensor are deteriorated, and there is a possibility that an alarm cannot be accurately issued.

  This problem is not limited to the contact combustion type gas sensor, but is a problem common to semiconductor type gas sensors.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to suppress deterioration in the accuracy of an alarm by suppressing deterioration in the characteristics of the gas sensor. To provide a gas alarm and a control method thereof.

Gas detector of the present invention is a gas detector for determining gas leakage by the resulting output by burning detection target gas by catalytic combustion type gas sensor, applying a voltage to the heater of the catalytic combustion type gas sensor Voltage applying means, first judging means for judging whether an absolute value of an output from the catalytic combustion type gas sensor is not less than a first threshold and less than a second threshold higher than the first threshold, and the catalytic combustion type Second determining means for determining whether the absolute value of the output from the gas sensor is greater than or equal to a second threshold value, and the absolute value of the output from the catalytic combustion gas sensor is greater than or equal to the first threshold value by the first determining means . If it is determined to be less than the second threshold value, it is determined that the gas leakage, after the lapse of the first delay time, have a row an alarm, the absolute value of the output from the catalytic combustion type gas sensor by the second determining means second Below threshold If it is determined to be, it determines that the spray state of chlorofluorocarbon, and outputs a signal to that effect to the alarm unit, after a delay time within a short 5 seconds than the first delay time or delay It is characterized by giving an alarm without time .

  According to this gas alarm device, it is determined whether the absolute value of the output from the gas sensor is equal to or greater than a second threshold value that is higher than the first threshold value, and it is determined that the absolute value of the output from the gas sensor is equal to or greater than the second threshold value. In this case, an alarm is issued after the second delay time shorter than the first delay time has elapsed. For this reason, when chlorofluorocarbon gas is sprayed on the gas sensor and the output from the gas sensor reaches an abnormal value, an alarm is issued early. As a result, the inspector can recognize his / her own error at an early stage, and can prompt the inspector to stop the spraying of Freon gas at an early stage. Therefore, carbonization of the chlorofluorocarbon gas is suppressed, and the deterioration of the accuracy of the alarm can be suppressed by suppressing the characteristic deterioration of the gas sensor.

The control method of the gas detector of the present invention is a control method of the gas detector for determining gas leakage by the output obtained by burning detection target gas by catalytic combustion type gas sensor, the catalytic combustion type gas sensor A voltage applying step of applying a voltage to the heater of the first , and determining whether an absolute value of an output from the catalytic combustion type gas sensor is not less than a first threshold and less than a second threshold higher than the first threshold . A determination step, a second determination step of determining whether an absolute value of the output from the catalytic combustion type gas sensor is equal to or greater than a second threshold, and an absolute value of the output from the catalytic combustion type gas sensor in the first determination step; If it is determined to be less than the first threshold value or more second threshold value, determines that gas leakage, after the lapse of the first delay time, have a row an alarm output from the catalytic combustion type gas sensor in said second determination step Of when the absolute value is determined to be more than the second threshold value, it determines that the spray state of chlorofluorocarbon, and outputs a signal to that effect to the alarm unit, a short five seconds than the first delay time after the delay time elapsed, or, without delay, and performs the alarm.

  According to the control method of the gas alarm device, it is determined whether the absolute value of the output from the gas sensor is equal to or higher than the second threshold value higher than the first threshold value, and the absolute value of the output from the gas sensor is equal to or higher than the second threshold value. If determined, an alarm is issued after the second delay time shorter than the first delay time has elapsed. For this reason, when chlorofluorocarbon gas is sprayed on the gas sensor and the output from the gas sensor reaches an abnormal value, an alarm is issued early. As a result, the inspector can recognize his / her own error at an early stage, and can prompt the inspector to stop the spraying of Freon gas at an early stage. Therefore, carbonization of the chlorofluorocarbon gas is suppressed, and the deterioration of the accuracy of the alarm can be suppressed by suppressing the characteristic deterioration of the gas sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the gas alarm which can suppress the characteristic deterioration of a gas sensor and can suppress the fall of the accuracy of an alarm, and its control method can be provided.

It is a block diagram which shows the gas alarm device which concerns on embodiment of this invention. It is an external view which shows the detail of the contact combustion type gas sensor shown in FIG. 1, (a) shows the top view, (b) has shown sectional drawing. FIG. 2B shows a cross section taken along the line AA in FIG. It is a graph which shows the output voltage of the contact combustion type gas sensor at the time of Freon gas spraying. It is a graph which shows the fluctuation amount of the output voltage of a contact combustion type gas sensor at the time of spraying CFC gas for 5 seconds. It is a graph which shows the fluctuation | variation amount of the output voltage of a contact combustion type gas sensor at the time of spraying CFC gas for 5 seconds, Comprising: It measures over a long term rather than the example shown in FIG. It is a flowchart which shows the control method of the gas alarm device which concerns on this embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a gas alarm device according to an embodiment of the present invention. As shown in FIG. 1, the gas alarm device 1 includes a control unit 10, a gas sensor unit 20 having a catalytic combustion type gas sensor 21, and an alarm unit (alarm means) 30, and the gas to be detected is detected by the catalytic combustion type gas sensor 21. The gas leakage is judged from the output obtained by burning the gas. In the following description, the catalytic combustion type gas sensor 21 is described as an example of a gas sensor. However, the gas sensor is not limited to the catalytic combustion type gas sensor 21 and may be a semiconductor type gas sensor.

  The control unit 10 performs drive control of the gas sensor unit 20, determination of gas leakage, and the like, and is configured by, for example, an MPU (Microprocessor Unit). The control unit 10 includes a sensor drive control unit 11, a sensor output acquisition unit 12, and a determination unit (determination unit) 13.

  The sensor drive controller 11 controls the drive of the catalytic combustion gas sensor 21 by outputting a drive signal. The sensor output acquisition unit 12 acquires information on the output voltage of the catalytic combustion gas sensor 21 that is driven and controlled by the sensor drive control unit 11. The determination unit 13 determines gas leakage based on the output voltage information acquired by the sensor output acquisition unit 12. Here, for example, the determination unit 13 determines whether or not the absolute value of the output voltage is greater than or equal to a first threshold (for example, 15 mV), and if it is determined that the output voltage is greater than or equal to the first threshold, it is a gas leak. Judge.

  In addition to the catalytic combustion gas sensor 21, the gas sensor unit 20 includes a resistor R3, a bridge drive circuit 22, an instrumentation amplifier 23, and an A / D converter 24.

  As shown in FIG. 1, the contact combustion type gas sensor 21 has two resistors (heaters) Rr and Rs, and these resistors Rr and Rs form a bridge circuit together with the resistors R1 and R2. The resistor R1 has one end connected to the bridge drive circuit 22 side and the other end connected to the connection point B. The resistor R2 has one end connected to the bridge drive circuit 22 side and the other end connected to the connection point A. The sensor resistor Rs is connected in series with the resistor R2, one end connected to the connection point A, and the other end connected to the ground. The reference resistor Rr is connected in series with the resistor R1, one end connected to the connection point B, and the other end connected to the ground.

  The bridge drive circuit 22 controls the voltage applied to the bridge circuit based on the drive signal from the sensor drive control unit 11. For this reason, the bridge drive circuit 22 constitutes a voltage application unit that controls the voltage applied to the catalytic combustion type gas sensor 21 together with the sensor drive control unit 11. The bridge drive circuit 22 is configured by, for example, a field effect transistor.

  FIG. 2 is an exploded perspective view showing details of the catalytic combustion type gas sensor 21 shown in FIG. The catalytic combustion type gas sensor 21 includes a sensor main part 21 ′ shown in FIG. 2 and resistors R 1 and R 2 provided on a base (not shown).

As shown in FIG. 2, the sensor resistor Rs is a resistor made of platinum, wound in a coil shape, and spanned between the first pin 21b and the second pin 21c penetrating the disc 21a. Yes. A catalyst layer 21s is provided around the sensor resistance Rs. The catalyst layer 21 s is made of, for example, Pd / Al ₂ O ₃ made of alumina supporting palladium.

  Like the sensor resistor Rs, the reference resistor Rr is a resistor made of platinum, wound in a coil shape, and spanned between the third pin 21d and the fourth pin 21e penetrating the disc 21a. . An alumina layer 21r is provided around the reference resistor Rr.

  Further, a shielding plate 21h is provided between the first and second pins 21b and 21c and the third and fourth pins 21d and 21e. The shielding plate 21h separates the sensor resistance Rs and the reference resistance Rr.

  Further, each of the above parts is covered with a case 21f. The case 21f is formed in a bottomed cylindrical shape, and a net portion 21g is provided at a portion corresponding to the bottom surface of the cylinder. For this reason, gas is introduced into the case 21f through the net 21g, and dust is prevented from entering by the net 21g.

  In addition, each pin 21b-21e has penetrated the disc 21a, and is installed in a base | substrate from the back surface of the disc 21a, and an electrical connection relationship will be ensured.

  Reference is again made to FIG. The instrumentation amplifier 23 amplifies the difference between the voltages input to the non-inverting input terminal and the inverting input terminal. The instrumentation amplifier 23 has a non-inverting input terminal connected to the connection point A and an inverting input terminal connected to the connection point B. For this reason, the instrumentation amplifier 23 amplifies the voltage difference between the connection point A and the connection point B. The instrumentation amplifier 23 is connected to a variable resistor R3. The variable resistor R3 is for adjusting the offset. The A / D converter 24 receives the analog voltage output from the instrumentation amplifier 23, performs A / D conversion, and outputs the analog voltage to the sensor output acquisition unit 12.

  The alarm unit 30 is configured by, for example, an audio output speaker or a lighting lamp. When the determination unit 13 determines that the absolute value of the output from the catalytic combustion gas sensor 21 is equal to or greater than the first threshold, the first delay An alarm is given after elapse of time (for example, 25 seconds).

  Further, in the present embodiment, the determination unit 13 has a function of determining whether the absolute value of the output from the catalytic combustion gas sensor 21 is equal to or higher than a second threshold value (for example, 60 mV) higher than the first threshold value. Here, when chlorofluorocarbon gas is sprayed on the catalytic combustion type gas sensor 21, for example, an output voltage of ± 60 mV or more tends to be obtained.

  FIG. 3 is a graph showing the output voltage of the catalytic combustion type gas sensor 21 at the time of chlorofluorocarbon spraying. FIG. 3 shows the output voltage when the CFC gas is sprayed from time 0 seconds to time 20 seconds. First, when chlorofluorocarbon gas is sprayed at time 0 second, the output voltage rises from about 10 seconds at the first gas sensor, and the output voltage reaches 300 mV at about 14 seconds. Next, the output voltage is maintained at 300 mV or more until about 20 seconds, and then the output voltage gradually decreases and reaches zero at about 31 seconds.

  Also, in the second gas sensor, when chlorofluorocarbon gas is sprayed at time 0 seconds, the output voltage rises from about 10 seconds, and the output voltage reaches 300 mV at about 18 seconds. Next, the output voltage is maintained at 300 mV or more until about 25 seconds, and then the output voltage gradually decreases and reaches zero at about 33 seconds.

  Further, in the third gas sensor, when the CFC gas is sprayed at time 0 second, the output voltage rises from about time 10 seconds, and the output voltage reaches 200 mV at time 12 seconds. Next, the output voltage gradually increases and reaches 300 mV at time 26 seconds. Thereafter, the output voltage gradually decreases and reaches zero at about 34 seconds.

  In the fourth gas sensor, when chlorofluorocarbon gas is sprayed at time 0 seconds, the output voltage falls from about 10 seconds, and the output voltage reaches −220 mV at time 16 seconds. Next, the output voltage is maintained at −220 mV or less until about 27 seconds, and then the output voltage gradually rises to zero at about 44 seconds.

  Thus, when CFC gas is sprayed, the absolute value of the output voltage from the catalytic combustion gas sensor 21 is equal to or higher than a second threshold value (for example, 60 mV) higher than the first threshold value. Therefore, the determination unit 13 determines whether the absolute value of the output is greater than or equal to the second threshold and determines whether or not the fluorocarbon gas is sprayed.

  Further, when the determination unit 13 determines that the fluorocarbon gas is sprayed, the determination unit 13 outputs a signal to that effect to the alarm unit 30. Thereby, the warning unit 30 issues a warning after the second delay time shorter than the first delay time has elapsed. For this reason, the gas alarm device 1 according to the present embodiment can prompt an inspector to stop the spraying of CFC gas at an early stage.

  More specifically, the second delay time is preferably zero seconds. That is, it is desirable that the alarm unit 30 issues an alarm without a delay time when the determination unit 13 determines that the fluorocarbon gas is sprayed. This is because it is possible to prompt the inspector to stop the spraying of Freon gas immediately.

  Further, the second delay time may be a time within 5 seconds. This point will be described in detail.

  FIG. 4 is a graph showing the fluctuation amount of the output voltage of the catalytic combustion type gas sensor 21 when the CFC gas is sprayed for 5 seconds. As shown in FIG. 4, the fluctuation amount (mV) is zero for any of the first to fourth gas sensors before CFC gas spraying. In this state, it is assumed that Freon gas is sprayed on each of the first to fourth gas sensors for 5 seconds, and then the first to fourth gas sensors are left for 1 hour. In this case, the fluctuation amount of the first gas sensor is about 7 mV, the fluctuation amount of the second gas sensor is about 4 mV, the fluctuation amount of the third gas sensor is about 0.5 mV, and the fluctuation amount of the fourth gas sensor is −2 mV. It is.

  FIG. 5 is a graph showing the fluctuation amount of the output voltage of the catalytic combustion type gas sensor 21 when the CFC gas is sprayed for 5 seconds, and is measured over a longer period than the example shown in FIG. As shown in FIG. 5, when each of the first to fourth gas sensors is sprayed with chlorofluorocarbon for 5 seconds, even when 24 hours have elapsed, the amount of fluctuation is almost the same as when 1 hour has passed as shown in FIG. For this reason, even if the time further elapses, it is estimated that the first to fourth gas sensors continue to maintain the fluctuation amount at the time when one hour has elapsed. In particular, the fluctuation amount shown in FIG. 5 is not greater than or equal to the first threshold used for determining gas leakage. For this reason, if it is spraying for about 5 seconds, it can be said that there is little influence with respect to the 1st threshold value for detecting a gas leak.

  From the above, it can be said that the second delay time may be within 5 seconds. In addition, when the second delay time is within 5 seconds, it is possible to prevent a situation in which a temporary miscellaneous gas such as an insecticide is detected and an alarm is issued.

  Next, the basic operation of the gas alarm device 1 according to this embodiment will be described. First, the sensor drive control unit 11 outputs a drive signal to the bridge drive circuit 22. Thereby, the contact combustion type gas sensor 21 becomes equal to or higher than the combustion temperature of the detection target gas, and the detection target gas burns in the atmosphere where the detection target gas exists. Here, the sensor resistance Rs burns the detection target gas, whereas the reference resistance Rr does not burn the detection target gas. For this reason, the sensor resistance Rs increases in temperature due to combustion of the detection target gas, but the reference resistance does not increase in temperature due to combustion of the detection target gas. And since a difference arises in temperature, a difference arises also in the resistance value of both resistances Rs and Rr, and the balance of a bridge circuit is broken. As a result, the output from the instrumentation amplifier 23 shows a value corresponding to the molecular weight (that is, the concentration) of the detection target gas.

  Next, the operation of the gas alarm device 1 according to this embodiment will be described. FIG. 6 is a flowchart showing a control method of the gas alarm device 1 according to the present embodiment. The process shown in FIG. 6 is repeatedly executed until the power of the gas alarm device 1 is turned off.

  First, it is assumed that the sensor drive control unit 11 outputs a drive signal, and the bridge circuit 22 applies a voltage to the catalytic combustion gas sensor 21. In this state, the sensor acquisition unit 12 acquires the output voltage (S1). Next, the determination unit 13 determines whether or not the absolute value of the output voltage is greater than or equal to the first threshold value (S2). When it is determined that the absolute value of the output voltage is not equal to or greater than the first threshold (S2: NO), the process proceeds to step S1.

  On the other hand, when it is determined that the absolute value of the output voltage is greater than or equal to the first threshold (S2: YES), the determination unit 13 determines whether the absolute value of the output voltage is greater than or equal to the second threshold (S3). . When it is determined that the absolute value of the output voltage is not greater than or equal to the second threshold value (S3: NO), the determination unit 13 determines that there is little possibility of the spraying of chlorofluorocarbon gas and it is a gas leak.

  Therefore, the determination unit 13 outputs a signal to that effect to the alarm unit 30, and the alarm unit 30 determines whether or not the first delay time has elapsed (S4). When it is determined that the first delay time has not elapsed (S4: NO), this process is repeated until it is determined that the first delay time has elapsed. On the other hand, when it is determined that the first delay time has elapsed (S4: YES), the process proceeds to step S6.

  By the way, when it is determined that the absolute value of the output voltage is greater than or equal to the second threshold value (S3: YES), the determination unit 13 determines that there is a high possibility of spraying of chlorofluorocarbon. Therefore, the determination unit 13 outputs a signal to that effect to the alarm unit 30, and the alarm unit 30 determines whether or not the second delay time has elapsed (S5). The second delay time may be zero seconds or may be a time up to 5 seconds.

  If it is determined that the second delay time has not elapsed (S5: NO), this process is repeated until it is determined that the second delay time has elapsed. On the other hand, when it is determined that the second delay time has elapsed (S5: YES), the process proceeds to step S6.

  In step S6, the warning unit 30 issues a warning (S6). Then, the process shown in FIG. 6 ends. As described above, it is possible to notify of gas leakage or chlorofluorocarbon gas spraying. In particular, since the second delay time is shorter than the first delay time and is zero second or 5 seconds at the maximum, the inspector can know the erroneous spray of Freon gas immediately or early.

  Thus, according to the gas alarm device 1 and its control method according to the present embodiment, it is determined whether the absolute value of the output from the catalytic combustion gas sensor 21 is equal to or higher than the second threshold value, which is higher than the first threshold value. When it is determined that the absolute value of the output from the catalytic combustion gas sensor 21 is equal to or greater than the second threshold value, an alarm is issued after the second delay time shorter than the first delay time has elapsed. For this reason, when chlorofluorocarbon gas is sprayed on the catalytic combustion type gas sensor 21 and the output from the catalytic combustion type gas sensor 21 reaches an abnormal value, an alarm is performed early. As a result, the inspector can recognize his / her own error at an early stage, and can prompt the inspector to stop the spraying of Freon gas at an early stage. Therefore, carbonization of the chlorofluorocarbon gas is suppressed, and deterioration of the characteristics of the catalytic combustion type gas sensor 21 can be suppressed, so that a reduction in alarm accuracy can be suppressed.

  In addition, when it is determined that the absolute value of the output from the catalytic combustion type gas sensor 21 is equal to or greater than the second threshold value, an alarm is issued without a delay time, so the inspector is immediately urged to stop spraying the CFC gas. It is possible to further suppress the deterioration of the characteristics of the contact combustion type gas sensor 21 and suppress the reduction of the accuracy of the alarm.

  In addition, when it is determined that the absolute value of the output from the catalytic combustion type gas sensor 21 is equal to or greater than the second threshold value, an alarm is issued after a delay time of 5 seconds or less. Can be urged to stop, and a situation where a temporary miscellaneous gas such as an insecticide is detected and an alarm is issued can also be prevented.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the above embodiment, the contact combustion type gas sensor 21 forms a bridge circuit by the reference resistance Rr, the sensor resistance Rs, and the fixed resistances R1 and R2, but these arrangements can be changed as appropriate.

  In the above embodiment, the catalytic combustion type gas sensor 21 forms a bridge circuit. However, the invention is not limited to this, and a catalytic combustion type gas sensor including a single heater may be used. Moreover, as long as it is a gas sensor which burns detection object gas with a heater, not only a contact combustion type gas sensor but a semiconductor type gas sensor etc. may be sufficient.

  Furthermore, in the above-described embodiment, the catalytic combustion gas sensor 21 may be one in which low temperature driving and high temperature driving are repeatedly controlled. In addition, regarding the alarm, the sound of gas leak and freon gas misspray may be different.

  In addition, the gas alarm device 1 according to the embodiment may be a gas fire alarm device integrated with a fire alarm device. In particular, in the case of a gas fire alarm, since the gas detection unit and the fire detection unit are close to each other, the error of the inspector is further increased, which is effective.

DESCRIPTION OF SYMBOLS 1 ... Gas detection apparatus 10 ... Control part 11 ... Sensor drive control part (voltage application means)
12 ... Sensor output acquisition unit 13 ... Determination unit (determination means)
DESCRIPTION OF SYMBOLS 20 ... Gas sensor part 21 ... Catalytic combustion type gas sensor 21a ... Disk 21b-21e ... Pin 21f ... Case 21g ... Net part 21h ... Shielding plate 21s ... Catalyst layer 21r ... Alumina layer 22 ... Bridge drive circuit (voltage application means)
23 ... Instrumentation amplifier 24 ... A / D converter 30 ... Alarm unit (alarm means)
Rs ... sensor resistance Rr ... reference resistance R1-R3 ... resistance

Claims (2)

A gas alarm device for judging gas leakage based on an output obtained by burning a gas to be detected by a contact combustion type gas sensor,
Voltage applying means for applying a voltage to the heater of the catalytic combustion gas sensor;
First determination means for determining whether an absolute value of an output from the catalytic combustion type gas sensor is equal to or higher than a first threshold and lower than a second threshold higher than the first threshold ;
Second determining means for determining whether the absolute value of the output from the catalytic combustion gas sensor is equal to or greater than a second threshold;
When it is determined by the first determination means that the absolute value of the output from the catalytic combustion type gas sensor is not less than the first threshold value and less than the second threshold value, it is determined that the gas leaks, and an alarm is issued after the first delay time has elapsed. There line,
If the absolute value of the output from the catalytic combustion type gas sensor by the second determining means is determined to be not smaller than the second threshold value, it determines that the spray state of chlorofluorocarbons, outputs a signal to that effect to the alarm unit In addition, the gas alarm device is characterized in that an alarm is issued after a delay time within 5 seconds shorter than the first delay time or without a delay time . A control method of a gas alarm device for judging a gas leak from an output obtained by burning a gas to be detected by a contact combustion type gas sensor,
A voltage application step of applying a voltage to the heater of the catalytic combustion gas sensor;
A first determination step of determining whether an absolute value of an output from the catalytic combustion type gas sensor is equal to or higher than a first threshold and lower than a second threshold higher than the first threshold ;
A second determination step of determining whether the absolute value of the output from the catalytic combustion gas sensor is equal to or greater than a second threshold;
When it is determined in the first determination step that the absolute value of the output from the catalytic combustion type gas sensor is not less than the first threshold value and less than the second threshold value, it is determined that the gas leaks, and an alarm is issued after the first delay time has elapsed. There line,
When it is determined in the second determination step that the absolute value of the output from the catalytic combustion type gas sensor is equal to or greater than the second threshold value, it is determined that the fluorocarbon gas is sprayed, and a signal to that effect is sent to the alarm unit. Outputs a warning after a delay time within 5 seconds shorter than the first delay time, or without a delay time
The method of gas detector, characterized in that.

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