JP2011232058A - Expired-air component measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an expired-air component measuring instrument which is capable of measuring expired-air components by reliably detecting feeding of expired air.SOLUTION: The expired-air component measuring instrument includes: a gas sensor 2 which is housed in a measuring device body so that expired air fed from an expired-air feeding port comes into contact with a gas sensitive body 20 comprising a metal oxide semiconductor; a thermistor 3 which is housed in the measuring device body so that the expired air fed from the expired-air feeding port comes into contact with a temperature sensing part; a differentiating circuit 4 for generating a differential output of a detected signal of the thermistor 3; and a microcomputer 7 which, upon detecting normal feeding of expired air on the basis of the differential output of the differentiating circuit 4, measures a gas concentration of a gas component to be detected in the expired air on the basis of a change in resistance at the gas sensitive body 20. When the differential output of the differentiating circuit 4 exceeds a predetermined expired-air determination value, the microcomputer 7 determines that the expired air has been fed. When the differential output of the differentiating circuit 4 falls below a predetermined interruption determination value before expiry of predetermined feeding time limit starting from the time of feeding determination, the microcomputer 7 determines that feeding of the expired air has been interrupted.

Description

  The present invention relates to an expiratory component measuring device for measuring the concentration of a detection target gas such as a bad breath causing gas or alcohol contained in exhaled breath.

  As a breath component measuring apparatus of this type, a metal oxide semiconductor gas sensor in which a heater is embedded in a gas-sensitive body made of a metal oxide semiconductor whose resistance value changes due to gas adsorption, and a built-in program are executed. A calculation processing unit for performing a measurement process for measuring a bad breath odor causing gas or alcohol concentration contained in exhaled air from a change in the resistance value of the gas sensitive body, and a display for displaying a measurement result of the calculation processing unit. A halitosis test apparatus is provided (see, for example, Patent Document 1).

  In such a breath odor inspection apparatus using a metal oxide semiconductor gas sensor, when a measurement start operation is performed after the power is turned on, the arithmetic processing unit controls the voltage applied to the heater of the gas sensor to a high voltage to control the high temperature state. The gas that has been created and burnt on the surface of the gas sensitive body before blowing in air is burned to clean the surface of the gas sensitive body. Then, after the cleaning of the gas sensitive body surface is completed and the measurement preparation is completed, when the subject blows exhaled air into the blowing port, the arithmetic processing unit starts measuring the exhaled component. For example, methyl mercaptan or the like When the bad breath odor causing gas is blown, the breath is detected by utilizing the decrease in the resistance value of the gas sensitive body.

  That is, the arithmetic processing unit switches the temperature of the gas sensitive body to a low temperature state after the end of the heat cleaning period, samples the resistance value of the gas sensitive body at a predetermined sampling interval, and decreases the resistance value. When the blow is determined, the bad breath intensity is inspected by comparing the resistance value of the gas sensitive body after a predetermined time with a reference value. The predetermined time is set to a time required until the change in resistance value is stabilized.

JP 2001-190523 A

  In the above breath odor test apparatus, it is determined that the breath is blown by detecting the falling edge of the resistance value of the gas sensitive body in a high temperature state of the gas sensitive body. For example, as shown in FIG. When the exhaled air is blown in, the resistance value Rs of the gas sensitive body is lowered, and the ratio (R0 / Rs) between the resistance value Rs and the reference resistance value R0 in the clean atmosphere is increased, so that the breath is blown. The gas concentration is determined after a predetermined time has elapsed.

  By the way, when the high-concentration halitosis factor gas is blown at time t2, when the resistance value Rs of the gas sensitive body is changed to an excessively low resistance value, the low-concentration halitosis factor gas is blown at time t3. The resistance value Rs of the gas sensitive body is increased as compared with that before blowing, and the resistance ratio (R0 / Rs) is decreased. Here, since the arithmetic processing unit determines whether the exhalation is blown from the falling edge of the resistance value of the gas sensitive body, that is, the rising edge of the resistance ratio (R0 / Rs), the exhalation is blown at time t3. However, if the resistance ratio decreases, there is a problem in that it is not possible to detect the exhalation of breath and the inspection of breath breath gas cannot be performed. In addition, in the case of a detection target gas whose resistance value increases as the concentration increases, exhalation of breath is detected by detecting the falling edge of the resistance ratio (R0 / Rs). The same problem occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an expiratory component measuring apparatus capable of detecting expiratory components reliably and measuring expiratory components.

  In order to achieve the above object, the invention of claim 1 is a measurement provided with an exhalation flow path for passing exhaled air that has been blown from a blowing port and an exhaust port for exhausting the exhaled air that has been blown into the exhaled flow path to the outside. A gas sensor body made of a metal oxide semiconductor whose resistance value changes according to the gas concentration of the gas to be detected, and a heater embedded in the gas sensor body, and exhaled air blown into the exhalation flow path A gas sensor housed inside the measuring instrument body so that at least a part of the gas sensor is in contact with the gas sensitive body, and a measurement start switch that generates a measurement start signal when an operation button exposed on the surface of the measuring instrument body is pressed; When the measurement start signal is input from the measurement start switch, the heater control starts to energize the heater, heats the gas sensitive body for a predetermined waiting time, and then provides a measurement period for measuring the gas concentration. A temperature sensor housed inside the measuring instrument body so that at least a part of the exhaled air that has been blown into the exhalation flow channel contacts the temperature sensing unit, and a differential output generator that generates a differential output of the detection signal of the temperature sensor When the differential output of the differential output generation unit exceeds a predetermined blowing determination value during the measurement period, it is determined that exhalation has been blown, and the differential output is interrupted for a predetermined period from the time of the blowing determination until the blowing time elapses. When the value falls below the determination value, the insufflation state detection unit determines that the exhalation of breath has been interrupted, and the insufflation state detection unit detects that the exhalation has been performed for a predetermined insufflation time necessary for measuring the gas concentration in the measurement period. And a gas concentration measuring unit that measures the gas concentration of the detection target gas component contained in the expiration based on a change in the resistance value of the gas sensitive body.

  According to a second aspect of the present invention, in the first aspect of the invention, the blowing state detection unit is configured so that the temperature detected by the temperature sensor when the measurement start signal is input is outside the temperature range set corresponding to the human body temperature. , Detecting the state of exhalation based on the differential output of the differential output generator, and if the detected temperature of the temperature sensor at the time of inputting the measurement start signal is within the above temperature range, A blowing state is detected.

  According to a third aspect of the present invention, in the first aspect of the invention, is the blowing state detection unit configured to determine whether the differential output of the differential output generation unit falls below a predetermined interruption determination value between the time of the blow determination and the time when the blow time elapses. Alternatively, when the resistance value of the gas sensitive body changes in the low concentration direction, it is determined that the exhalation of breath is interrupted.

  According to a fourth aspect of the present invention, in the gas sensor according to any one of the first to third aspects, the gas sensor includes a pair of heater electrode terminals to which both ends of the heater are electrically connected, and one end to the gas sensitive body. A sensor board on which at least a gas sensor is mounted, and a main board on which circuits of at least a heater control unit and a gas concentration measuring unit are formed. A board-to-board connector that electrically connects between the pair of heater electrode terminals is connected to each of the pair of heater electrode terminals to energize the heater, and each heater electrode is connected to the pair of heater electrode terminals. A pair of voltage measurement terminals for measuring the voltage value of the terminals, and the heater control unit obtains the heater voltage from the voltage between the terminals of the pair of voltage measurement terminals, and the heater voltage is a desired voltage. And controlling the power supply to the heater to a value.

  According to the first aspect of the present invention, when the exhaled breath is blown from the exhalation blowing port, the fact that the detected temperature of the temperature sensor changes in a direction approaching the expiratory temperature is used, and the differential output of the detection signal of the temperature sensor is the blowing determination If the value exceeds the value, it is determined that exhalation has been blown, and if the differential output falls below the interruption determination value between the time of the blow determination and the expiration of the blow time, it is determined that the blow has been interrupted. Compared with the case where the exhalation of breath is detected from the change in the resistance value of the body, the inhalation of exhalation or the interruption of the insufflation can be reliably determined, and the measurement of the gas concentration can be started.

  In addition, when the ambient temperature is within the temperature range set corresponding to the human body temperature, there is a risk of false detection if breathing in is determined using the detection signal of the temperature sensor. For example, if the detected temperature at the start of measurement is within the above-mentioned temperature range, it is possible to reduce the possibility of erroneously detecting the exhalation of breath because the exhalation of breath is determined from the change in resistance value of the gas sensitive body.

  According to the invention of claim 3, since not only the differential output of the detection signal of the temperature sensor but also the resistance value of the gas sensitive body changes in the low concentration direction, it is possible to detect the interruption of blowing.

  By the way, when the heater voltage is detected from the voltage of the pair of energization terminals through which the heater drive current flows, the detection is performed including the voltage drop due to the contact resistance of the board-to-board connector. However, according to the invention of claim 4, since the heater voltage is measured from the voltage between terminals of the voltage measurement terminal where the heater drive current does not flow, the voltage drop due to the contact resistance can be reduced. Therefore, since the heater voltage can be measured more accurately, the heating value of the heater, that is, the temperature of the gas sensitive body can be controlled accurately.

It is a circuit diagram of the bad breath measuring instrument of this embodiment. It is a flowchart same as the above. It is a side view which can partly fracture | rupture the metal oxide semiconductor gas sensor used for the same as the above. It is a figure which shows the result of having measured the secondary differential value of the resistance value of a gas sensitive body same as the above. The same breath odor measuring device is shown, (a) is a front view, (b) is a right side view, (c) is a rear view, and (d) is a bottom view. It is a disassembled perspective view of a sensor block same as the above. It is sectional drawing of the principal part same as the above. It is a wave form diagram explaining operation | movement of the conventional breath measuring device.

  Hereinafter, an embodiment in which the technical idea of the present invention is applied to a breath odor measuring device that measures the concentration of a breath odor causing gas contained in exhaled breath will be described with reference to the drawings.

  FIG. 1 shows a circuit diagram of a breath odor measuring device A of the present embodiment. The breath odor measuring device A includes a battery power source 1 of a low voltage (for example, 3V) such as a dry battery or a rechargeable battery, a metal oxide semiconductor gas sensor (hereinafter abbreviated as a gas sensor) 2, a thermistor 3 (temperature sensor), and a thermistor 3 A differential circuit 4 (differential output generator) for generating a differential output of the detection signal, a heater drive circuit 5 for energizing a heater built in the gas sensor 2, a liquid crystal display (hereinafter referred to as LCD) 6, and a heater drive Functions such as a heater control unit that controls the drive of the circuit 5 and a gas concentration measurement unit that measures the gas concentration of the detection target gas from the resistance value of the gas sensitive body 20 described later are programmed, and also has a driver function of the LCD 6. A microcomputer (hereinafter abbreviated as “microcomputer”) 7 that performs control processing for the entire measuring instrument, and judgment of calibration data and bad breath intensity (concentration of bad breath factor gas) of the gas sensor 2 A memory 8 consisting of non-volatile memory (e.g., EEPROM, etc.) that stores a reference value of the order, and a measurement start switch SW1 as a major component.

  The components of the circuit shown in FIG. 1 are divided and mounted on two printed wiring boards (sensor substrate 10a and main body substrate 10b). On one sensor board 10a, circuit elements including at least the gas sensor 2, the thermistor 3, and the memory 8 are mounted. Circuit elements including at least the differentiation circuit 4, the heater drive circuit 5, the LCD 6, and the microcomputer 7 are mounted on the other body substrate 10b. The sensor board 10a and the main board 10b are electrically connected via inter-board connectors (hereinafter abbreviated as connectors) CN1 and CN2.

As shown in FIG. 3, the gas sensor 2 includes a gas sensitive body 20 formed in an elliptical shape by a metal oxide semiconductor (for example, SnO ₂ ) whose resistance value changes according to the gas concentration of the detection target gas. The gas sensitive body 20 is embedded with a heater combined electrode 21 formed in a coil shape from a noble metal wire (for example, Pt) and penetrates the center of the heater combined electrode 21 so as to penetrate the noble metal wire (for example, Pt). Etc.), one end side of the detection electrode 22 formed in a rod shape is embedded in the gas sensitive body 20.

  The gas sensor 2 is substantially cylindrical and has a metal cap 24 having a gas introduction hole 24a opened on the upper surface and the entire lower surface opened, and a resin press-fitted and fixed to the opening on the lower surface side of the cap 24. A base 25 made of metal and three terminals 26a, 26b, and 26c that pass through the base 25 and project into and out of the sensor casing (comprising the cap 24 and the base 25) are provided. Both ends 21a and 21b of the heater combined electrode 21 are connected to the terminals 26a and 26c, respectively, and the other end side of the detection electrode 22 is connected to the terminal 26b, whereby the gas sensitive body 20 is supported and fixed to the terminals 26a to 26c. Has been. Further, a stainless steel wire mesh 27 is attached to the gas introduction hole 24a on the upper surface of the cap 24, and dust and the like are prevented from entering the gas introduction hole 24a.

  FIGS. 5A to 5D are views showing the whole breath odor measuring device A, and the measuring device main body 30 of the breath odor measuring device A is a front case 32 made of a synthetic resin molded product (for example, ABS resin). And the sensor block 34 which accommodated the gas sensor 2 and the thermistor 3 is attached to the case 31 comprised by assembling the rear case 33, and it is comprised. Note that a plurality of slits 32 a communicating between the inside and the outside of the case 31 are opened at portions located on the side of the sensor block 34 on the left and right side walls of the front case 32.

  As shown in FIGS. 6 and 7, the sensor block 34 has the gas sensor 2 mounted inside a case formed by assembling a front case 35 and a rear case 36 each made of a synthetic resin molded product (for example, ABS resin). The sensor substrate 10a is accommodated. The front case 35 has a substantially box shape with an open rear surface, and is integrally provided with claw pieces 35b protruding rearward from the rear edges of the left and right side walls. The rear case 36 has a substantially box shape with an open front surface, and is provided with recesses 36b on the inner side surfaces of the left and right side walls for engaging the claw pieces 35b. Thus, the front case 35 and the rear case 36 are temporarily fixed to each other by engaging the claw piece 35b with the recess 36b. Then, a tapping screw 45 passed from the rear through an insertion hole (not shown) provided in the rear case 36 is passed through the hole of the sensor substrate 10a and screwed into a screw hole (not shown) of the front case 35, The rear case 36 and the front case 35 are fixed, and the sensor substrate 10a is positioned. Note that the left and right side walls of the front case 35 and the rear case 36 are formed with notches 46a and 46b at portions that are abutted during assembly. When the front case 35 and the rear case 36 are assembled, these notches 46a and 46b are formed. A vent hole 46 is formed by the notches 46a and 46b to communicate the inside and the outside of the case. The rear case 36 is also formed with a notch 36c that exposes the connector CN1 mounted on the sensor substrate 10a. The sensor block 34 is connected to the case 31 with the connector CN1 connected to the connector CN2 provided on the case 31 side. It is attached to.

  A concave portion 35a that is recessed in a round hole shape is provided on the front surface of the front case 35, and a rear end portion of a cylindrical mouthpiece 37 is inserted into the concave portion 35a. A through-hole 35b communicating with the expiratory air passage inside the mouthpiece 37 is provided on the bottom surface of the recess 35a.

  On the other hand, the rear case 36 has a round hole-shaped exhaust port 36 a at a position corresponding to the through hole 35 b of the front case 35.

  A cap member 38 made of a synthetic resin molded product such as ABS resin is attached to the gas sensor 2 mounted on the sensor substrate 10a. As shown in FIGS. 6 and 7, the cap member 38 is provided with a storage hole 39 having a round hole shape having an inner diameter slightly larger than the outer diameter of the cap 24 of the gas sensor 2. The cap 24 is inserted. A step portion 39 a is provided in the back of the storage recess 39, and the gas sensor 2 is stored in a state in which an expiratory reservoir space 43 is provided between the bottom portion of the storage recess 39 and the step portion 39 a hits the tip side of the cap 24. It is stored in the recess 39. The cap member 38 has a ventilation hole 42 communicating with the expiratory reservoir space 43 and the outside.

  Further, the cap member 38 is provided with a ventilation channel 40 that communicates between the through hole 35 b of the front case 35 and the exhaust port 36 a of the rear case 36. The ventilation channel 40 has an inner diameter on the exhaust side that is smaller than that on the blowing side, and is accommodated from the large-diameter hole 40b in a portion close to the small-diameter hole 40b on the inner peripheral surface of the large-diameter hole 40a. An introduction hole 41 for introducing exhalation into the recess 39 is formed. The introduction hole 41 is formed so as to be displaced from the gas introduction hole 24 a provided in the center of the ceiling surface of the cap 24. Further, the cap member 38 is provided with a holding hole 44 that communicates the inner peripheral surface of the small-diameter hole 40b with the outside at a portion near the exhaust port 36a in the small-diameter hole 40b. The thermistor 3 is inserted into the holding hole 44 from the outside, and the temperature sensing part of the thermistor 3 is arranged near the center of the small-diameter hole 40b. In addition, the position B enclosed by the dotted line in FIG. 7 has shown the position where the temperature sensing part of the thermistor 3 is arrange | positioned. The thermistor 3 is electrically connected to the sensor substrate 10a via a lead wire 3a.

  Therefore, the exhaled air blown into the mouthpiece 37 flows into the large-diameter hole 40a of the ventilation channel 40 provided in the cap member 38, and most of the exhaled air is discharged to the outside through the small-diameter hole 40b. . Further, when exhalation flows from the large diameter hole 40a into the small diameter hole 40b, pressure loss occurs because the inner diameter of the hole becomes small, and a part of the exhalation passes through the introduction hole 41 into the exhalation accumulation space 43. It is introduced and discharged from the ventilation hole 42 to the outside of the cap member 38. Further, the exhaled air that has flowed into the exhalation reservoir space 43 enters the inside of the cap 24 from the gas introduction hole 24a provided in the cap 24, and the gas sensor 2 measures the concentration of the detection target gas in the exhaled air.

  Here, the exhaled air to be introduced from the exhalation flow path 40 to the gas sensitive body 20 in the gas sensor 2 passes through the introduction hole 41 extending in a direction perpendicular to the direction of flowing in the exhalation flow path 40 and this introduction. The air is introduced into an expiratory reservoir space 43 that is larger than the hole 41, and hits the outer peripheral edge of the cap 24 surrounding the gas introducing hole 24 a in the expiratory reservoir space 43. Then, after exhalation is once trapped in the exhalation reservoir space 43, the exhalation is introduced into the cap 24 through the gas introduction hole 24a and comes into contact with the gas sensitive body 20. Therefore, even if the flow rate and pressure of the exhaled breath blown into the mouthpiece 37 by the user is large, the exhaled air is not directly blown onto the sensitive body 20, and thus the sensitive body 20 is rapidly cooled by the exhaled breath. No, the temperature change of the gas sensitive body 20 can be reduced and more accurate measurement can be performed. Moreover, the exhaled air blown from the mouthpiece 37 passes through the exhalation flow path 40 and the introduction hole 41 into the exhalation reservoir space 43 in a short time, and is introduced from the exhalation reservoir space 43 into the cap 24 of the gas sensor 2. Therefore, the response speed of the output of the gas sensitive body 20 can be increased.

  Furthermore, since the cap member 38 is provided with a ventilation hole 42 that allows the expiration reservoir space 43 to communicate with the outside, the expiration trapped in the expiration reservoir space 43 and the cap 24 during the measurement is performed in the ventilation hole 42 and the ventilation hole. 46 and the slit 32a provided in the front case 32 are quickly replaced with clean air after measurement. Therefore, even when the expiration is continuously measured or when the low-concentration exhalation is measured after the high-concentration exhalation is measured, the exhalation is not easily trapped inside the expiratory collection space 43 or the cap 24. Therefore, it is possible to reduce the influence of exhalation at the time of the previous measurement and perform accurate measurement.

  As described above, the gas sensor 2 is housed inside the measuring device main body 30 so that at least a part of the exhaled air that is blown from the through hole 35b (exhalation blowing port) of the measuring device main body 30 contacts the gas sensitive body 20. . The resistance value of the gas sensitive body 20 changes according to the gas concentration of the gas to be detected that is in contact with the gas sensitive body 20, and in this sensor, a detection electrode having one end electrically connected to the gas sensitive body 20 The resistance value of the gas sensing body 20 is measured from the resistance value between the heater 22 and the ground-side terminal 21 b of the heater electrode 21. In the present embodiment, the microcomputer 7 takes in the voltage VS generated between the detection electrode 22 and the terminal 21b, and measures the resistance value of the gas sensitive body 20 as the detection voltage VS.

  Here, the high potential side terminal 21a of the heater combined electrode 21 is connected to the first and second pins of the connector CN1, and the ground side terminal 21b of the heater combined electrode 21 is connected to the fourth and fifth pins of the connector CN1, respectively. Further, the other end of the detection electrode 22 is connected to the third pin of the connectors CN1 and CN2. The first pin of the connector CN2 is connected to the positive electrode of the battery power source 1 via a PNP transistor Q1, and the fifth pin of the connector CN2 is connected to the negative electrode of the battery power source 1. The heater drive circuit 5 includes the transistor Q1, the resistor R1 connected between the base and emitter of the transistor Q1, and the resistor R2 connected between the base of the transistor Q1 and the output port PO1 of the microcomputer 7. . When the transistor Q1 is turned on according to the control signal from the microcomputer 7, the battery power source 1 → the transistor Q1 → the first pin of the connectors CN1 and CN2 → the heater combined electrode 21 → the fifth pin of the connectors CN1 and CN2 → the battery power source 1 The heater current (drive current) flows through the path, and the gas sensitive body 20 is heated by the heat generated by the heater serving electrode 21.

  Further, the 2nd and 4th pins of the connector CN2 are connected to the A / D input ports PI2 and PI3 of the microcomputer 7, respectively. The microcomputer 7 detects the voltages VH1 and VH2 at both ends 21a and 21b of the heater combined electrode 21 by A / D converting the voltages input to the A / D input ports PI2 and PI3, respectively, and the difference between them (VH1 The heater voltage VH applied to the heater combined electrode 21 is measured by calculating -VH2). And the microcomputer 7 as a heater control part is changing the on-duty of the transistor Q1 so that the heater voltage VH may become a desired voltage value, and is controlling the temperature of the gas sensitive body 20 to desired temperature. .

  Here, while the resistance value of the heater combined electrode 21 made of a noble metal wire is about 3Ω, the contact resistance between the connectors CN1 and CN2 is relatively large at about 0.2Ω, so the heater combined electrode 21 (heater) When the heater voltage is measured between the first pin and the fifth pin of the connector CN2 through which the drive current flows, the heater voltage is measured including the voltage drop due to the contact resistance between the connectors CN1 and CN2. VH cannot be measured accurately.

  Therefore, in this embodiment, in order to detect the heater voltage VH, not the voltage between the 1st pin and the 5th pin through which the heater current flows, but the 2nd pin and the 4th pin to which both ends of the heater electrode 21 are connected, respectively. The voltages VH1 and VH2 are measured respectively. Only a very small current for voltage detection flows through the 2nd pin and the 4th pin, and this current is much smaller than the driving current of the heater. Therefore, the voltage drop due to the contact resistance between the connectors CN1 and CN2 Becomes small enough to be ignored, and the heater voltage VH (= VH1−VH2) can be accurately detected.

  Further, the third pin of the connector CN2 is connected to the positive electrode of the battery power source 1 through a series circuit including the load resistor R3 and the transistor Q2, and is also connected to the input port PI1 of the microcomputer 7. When measuring the resistance value of the gas sensitive body 20, the microcomputer 7 turns on the transistor Q2 while the transistor Q1 of the heater driving circuit 5 is turned off, and the series circuit of the load resistor R3 and the gas sensitive body 20 is turned on. A voltage VC is applied to the first electrode 21 and a divided voltage VS generated between the ground-side terminal 21b of the heater serving electrode 21 and the detection electrode 22 is taken in as a detection voltage from the input port PI1. The microcomputer 7 obtains the voltage dividing ratio with the resistor R3 from the divided voltage VS, and obtains the resistance value of the gas sensitive body 20 using the voltage dividing ratio and the resistance value (known) of the resistor R3. The gas concentration is detected based on the resistance value of the gas sensitive body 20.

  Further, in the present embodiment, as described above, the thermistor 3 is provided to detect the exhalation of the exhaled air from the exhaled air inlet, and at least a part of the exhaled air blown from the exhaled air inlet is temperature sensitive. It is housed inside the measuring instrument main body so as to contact the part. One end of the thermistor 3 is connected to the 6th pin of the connectors CN1 and CN2, and is connected to the positive electrode of the battery power supply 1 via the connectors CN1 and CN2. The other end of the thermistor 3 is connected to the 13th pin of the connectors CN1 and CN2, and one end of the resistor R4 is connected to the 13th pin of the connector CN2. The other end side of the resistor R4 is connected to the negative electrode of the battery power source 1, and the battery power source 1 is applied to a series circuit of the thermistor 3 and the resistor R4. Since the resistance value of the thermistor 3 changes as the temperature rises, the voltage dividing ratio changes, the voltage across the resistor R4 changes, and the voltage across the resistor R4 is input to the differentiation circuit 4 using the operational amplifier OP1. .

  The differentiation circuit 4 includes an operational amplifier OP1, a parallel circuit of a resistor R5 and a capacitor C1 connected between the output terminal and the inverting input terminal of the operational amplifier OP1, and a capacitor C2 connected between the inverting input terminal of the operational amplifier OP1 and the ground. The high voltage side end of the resistor R4 is input to the non-inverting input terminal of the operational amplifier OP1. Here, switches SW2 and SW3 are connected between the non-inverting input terminal and the output terminal of the operational amplifier OP1, and between the non-inverting input terminal and the inverting input terminal, respectively. These switches SW2 and SW3 are controlled to be turned on / off by a control signal output from the output port PO3 of the microcomputer 7. When the switches SW2 and SW3 are turned on, the non-inverting input terminal and the output terminal of the operational amplifier OP1 and the non-inverting input terminal and the inverting input terminal are short-circuited, and the capacitor C2 is rapidly charged to the voltage across the resistor R4. Therefore, it is possible to prevent the initial value of the differential output from the differentiating circuit 4 from becoming an excessive value.

  Further, a series circuit of the measurement start switch SW1 and the resistor R6 is connected between both ends of the battery power supply 1, and the voltage at the connection point between the measurement start switch SW1 and the resistor R6 is input to the input port PI5 of the microcomputer 7. Yes.

  Here, the operation of the present embodiment will be described based on the flowchart of FIG. When a power switch (not shown) is turned on, the microcomputer 7 executes an initialization operation, reads various setting data and calibration data from the memory 8, and shifts to a standby mode. In the standby state, the microcomputer 7 periodically monitors the voltage level of the input port PI5. When the user presses the measurement start switch SW1 (hereinafter referred to as switch SW1), the input port PI5 is set to the H level. When the pulse signal is input, the microcomputer 7 ends the standby mode and starts a control process for measuring the gas concentration of the bad breath causing gas according to the program (step ST1 in FIG. 2).

  First, the microcomputer 7 outputs a pulse signal having a predetermined cycle with a predetermined on-duty from the output port PO1 to turn on / off the transistor Q1. During the on-period of the transistor Q1, the heater combined electrode is provided via the transistor Q1. Power is supplied to 21. At this time, the average voltage applied to the heater combined electrode 21 is about 0.9 V by duty control, and the gas sensitive body 20 is heated to a temperature of, for example, about 400 ° C. by the heat generated by the heater combined electrode 21, and is sensed when not in use. Heat cleaning is performed by burning miscellaneous gas or the like in contact with the surface of the gas body 20.

  At the start of measurement, the microcomputer 7 outputs an on control signal from the output port PO3, and turns on the switches SW2 and SW3 for 1 second (step ST2). When the switches SW2 and SW3 are both turned on, the non-inverting input terminal and the output terminal of the operational amplifier OP1 are short-circuited, and the non-inverting input terminal and the inverting input terminal are short-circuited. Therefore, the capacitor C2 is rapidly charged to the divided voltage V1 (the voltage across the resistor R4) determined by the resistance ratio between the resistance value of the thermistor 3 and the resistance value of the resistor R4.

  When one second has elapsed after the switches SW2 and SW3 are turned on, the microcomputer 7 takes in the divided voltage V1 from the input port PI4, calculates the resistance value of the thermistor 3 from the divided voltage V1, and the resistance value of the thermistor 3 Based on the above, the detected temperature Tp at the start of measurement is calculated. When the calculation of the detected temperature Tp is completed, the microcomputer 7 outputs an off control signal from the output port PO3 to turn off the switches SW2 and SW3. When the switches SW2 and SW3 are turned off, the short-circuit state between the non-inverting input terminal and the output terminal of the operational amplifier OP1 and the short-circuit state between the non-inverting input terminal and the inverting input terminal are released, and the divided voltage V1 is differentiated. The signal is input to the circuit 4 (step ST3).

  Next, the microcomputer 7 serving as the blowing detection unit compares the detected temperature Tp calculated in step ST3 with a predetermined reference temperature (for example, 33 ° C.) (step ST4), and breaths are blown based on the comparison result. It is determined whether or not the temperature detected by the thermistor 3 is used for the determination. Here, if the detected temperature Tp at the start of measurement is outside the temperature range set corresponding to the human body temperature, the detected temperature of the thermistor 3 changes greatly when exhalation is blown. Although it is easy to detect the exhaled breath from the temperature change, it is considered that the detected temperature of the thermistor 3 does not change much even when exhaling is in the above temperature range, and it is difficult to detect the exhaled breath. Therefore, if the detected temperature Tp at the start of measurement is lower than 33 ° C., the microcomputer 7 uses the thermistor 3 to detect the exhalation of breath (step ST5), and the detected temperature Tp at the start of measurement is 33 ° C. or higher. If there is, the thermistor 3 is not used for the detection of the exhalation of breath, and the exhalation of breath is detected from the change in the resistance value of the gas sensitive body 20 (step ST6). In this embodiment, the microcomputer 7 compares the detected temperature Tp at the start of measurement with a temperature range (33 ° C. or higher) set corresponding to the human body temperature, and the detected temperature Tp at the start of measurement is the above temperature. If it is outside the range, that is, if the detected temperature Tp is less than 33 ° C., the detected temperature Tp of the thermistor 3 is used for blowing determination, but an upper limit value may be provided in the above temperature range. That is, if the temperature range corresponding to human body temperature is, for example, 33 ° C. or more and 43 ° C. or less, and the detected temperature Tp at the start of measurement is outside the above temperature range (Tp <33 ° C. or Tp> 43 ° C. ) If the detected temperature Tp of the thermistor 3 is used for the blow determination and the detected temperature Tp is within the above temperature range, the detected temperature Tp of the thermistor 3 is not used for the blow determination, and the resistance value change of the gas sensitive body 20 is detected. You may make it perform blowing detection. When the ambient temperature is equal to or higher than the human body temperature, the detected temperature Tp at the start of measurement may be compared with only the upper limit value of the above temperature range, and the detected temperature Tp exceeds the upper limit value (for example, 43 ° C.). If the detected temperature Tp of the thermistor 3 is used for the blow determination, and the detected temperature Tp is equal to or lower than the upper limit value, the detected temperature Tp of the thermistor 3 is not used for the blow determination, and the resistance value change of the gas sensitive body 20 is changed. The blowing detection may be performed.

  In the microcomputer 7, when the temperature determination of the thermistor 3 is completed, a signal for turning on the transistor Q2 at a timing at which the transistor Q1 is turned off, for example, every 0.1 second until 2.5 seconds after the switch SW1 is operated. Is output from the output port PO3, the gas sensitive body 20 is energized through the load resistor R3, and the voltage VS across the gas sensitive body 20 is taken in from the input port PI1 and stored in the memory 8 sequentially.

  Then, the microcomputer 7 obtains the secondary differential value VS ″ of the detection voltage VS when 2.5 seconds have elapsed from the time when the switch SW1 is pressed (step ST7), and sets the magnitude of the secondary differential value VS ″. The heat cleaning time (standby time) is determined accordingly.

  By the way, when the switch SW1 is pressed to start measurement, heating of the gas sensitive body 20 is started, and the surface of the gas sensitive body 20 is contacted when not in use until a predetermined time elapses from the start of heating. A heat cleaning time for cleaning by burning miscellaneous gas or the like is set, and after the heat cleaning time has elapsed, the expiration component is measured. Here, the longer the leaving period when the breath breath odor measuring device A (exhalation measuring device) is not used, the longer the time required for heat cleaning, so conventionally, the heat cleaning time was set longer, but the measurement was performed as soon as possible. There is a user's desire to perform this, and in this breath odor measuring device A, when the leaving period from the previous measurement is short, the heat cleaning time is shortened to shorten the time until measurement. When the standing period from the previous measurement is short, there is little dirt such as miscellaneous gas in contact with the surface of the gas sensitive body 20, and the resistance value of the gas sensitive body 20 changes rapidly in a short time. When the leaving period is long, there is a lot of dirt such as miscellaneous gas in contact with the surface of the gas sensitive body 20, and therefore the resistance value of the gas sensitive body 20 slowly changes (gradual increase or decrease) over a long period of time. Conceivable. Therefore, the microcomputer 7 determines that the standing period from the previous measurement is shorter as the secondary differential value VS "of the detected voltage obtained in step ST7 is larger, and sets the heat cleaning time to be shorter. The smaller the value VS ", the longer the heat cleaning time is set because it is determined that it has been left for a long time since the previous use.

  Here, if the detected voltages at times (t1−Δt), t1, (t1 + Δt) are VS1, VS2, and VS3, respectively, the second-order differential value VS ″ of the detected voltage VS at time t1 is an average value of VS1 and VS3. Is obtained by dividing VS2.

VS "= VS2 * 2 / (VS1 + VS3)
In this embodiment, the addition average value of the detection voltages VS is used for each of VS1, VS2, and VS3, and the microcomputer 7 uses the following equation (1) to calculate 1 from the time when the switch SW1 is pressed. The second-order differential value VS ″ at the 8th second is calculated. Note that VS (t) is the detection voltage VS of the gas sensitive body 20 when t seconds have elapsed since the measurement start switch SW1 was pressed.

  When the microcomputer 7 calculates the secondary differential value VS ″ at 1.8 seconds from the time when the switch SW1 is pressed, the secondary differential value VS ″ is normalized by dividing by a predetermined constant and then normalized. The level of the secondary differential value VS ″ is compared with a predetermined reference value (for example, 1) (step ST8). If the normalized secondary differential value VS ″ is 1 or more in the determination process of step ST8, The microcomputer 7 determines that the leaving period is short and sets the heat cleaning time to 5 seconds (step ST9). On the other hand, if the normalized secondary differential value VS ″ is less than 1 in the determination process of step ST8, the microcomputer 7 determines that the normalized secondary differential value VS ″ and a predetermined reference value (for example, 0.6 ) (Step ST10), and if the secondary differential value VS "after normalization is 0.6 or more and less than 1, it is determined that the measurement is performed for the first time after the measurement of the high concentration gas, and the heat The cleaning time is set to 15 seconds (step ST11). If the secondary differential value VS "after normalization is less than 0.6, the microcomputer 7 determines that the product is a long-term neglected product, and the heat cleaning time. Is set to 20 seconds (step ST12).

  FIG. 4 shows the measurement data of secondary differential values in various atmospheres (six types of exhaled gas and 1 mg / L reference gas) for three types of samples (long-term neglected products A and B and normal product C). The long-term neglected products A and B have a second order differential value larger than that of the normal product. In the figure, ▲ is the long-term abandoned product A, ■ is the long-term abandoned product B, and ♦ is the normal product data.

  When the heat cleaning time (standby time) is determined by the determination process described above, the microcomputer 7 performs heat cleaning by burning miscellaneous gas and the like adhering to the surface of the gas sensitive body 20 until the heat cleaning time ends. In preparation for the start of measurement of the detection target gas.

  When the heat cleaning time ends (step ST13), the microcomputer 7 informs the user that the measurement preparation is completed by blinking a display lamp (not shown) or sounding a buzzer, and injects exhalation. Encourage and prepare for exhalation.

  Here, the subsequent operation differs depending on whether or not the thermistor 3 is used for the determination of exhalation of breath. First, the operation when the thermistor 3 is used will be described (YES in step ST14).

  The microcomputer 7 sequentially receives the thermistor output VTH (differential output of the divided voltage V1) output from the differentiating circuit 4 from the input port PI4 (for example, every 0.1 second), and obtains the thermistor output VTH0 at the end of the heat cleaning period. The reference value is stored in the memory 8 (step ST15), and the thermistor output VTH at each capture time is also stored in the memory 8.

  Next, the microcomputer 7 compares the level of the current thermistor output VTH with the value obtained by adding 0.3 V to the reference value VTH0 (injection determination value) (step ST16).

  Here, when the current thermistor output VTH does not continue for 0.5 seconds (NO in step ST <b> 16), a state in which the current thermistor output VTH exceeds the value obtained by adding 0.3 V to the reference value VTH <b> 0 (injection determination value), the microcomputer 7 It is determined whether 6 seconds have elapsed since the end of the cleaning period (step ST18). If 6 seconds have elapsed (YES in step ST18), even if 6 seconds have elapsed since the end of heat cleaning. It is determined that exhalation has not been performed, and an error is displayed on the LCD 6 (step ST25).

  On the other hand, when the current thermistor output VTH continues to exceed the value obtained by adding 0.3 V to the reference value VTH0 (injection determination value) for 0.5 seconds (YES in step ST16), the microcomputer 7 detects the thermistor 3. Since the differential output of the signal exceeds the inhalation determination value, it is determined that exhalation has been inhaled, the value of the thermistor output VTH up to the present is read from the memory 8, and the peak value VTHM of the thermistor output VTH is extracted (step) ST17) It is determined whether the current thermistor output VTH is higher or lower than 60% of the peak value VTHM (interruption determination value) (step ST19).

  Here, as a result of the determination in step ST19, if the current thermistor output VTH is less than 60% of the peak value VTHM (interruption determination value) (NO in step ST19), the microcomputer 7 blows in the breath quickly. It is determined that the detected temperature of the thermistor 3 has been lowered because it has been interrupted at the stage (within 3 seconds from the detection of blowing), and the fact that the early blowing interruption has occurred is displayed on the LCD 6 (step ST21).

  If the current thermistor output VTH is higher than 60% of the peak value VTHM as a result of the determination in step ST19 (YES in step ST19), the microcomputer 7 determines that the exhalation is continuing, It is determined whether or not 3 seconds have elapsed since the detection of blowing (step ST20).

  Here, if 3 seconds have not elapsed since the detection of blowing (NO in step ST20), the microcomputer 7 returns to step ST17 and repeats the above processing. On the other hand, if 3 seconds have passed since the detection of the blow (YES in step ST20), the microcomputer 7 measures the sensor voltage VS at the third second and the sensor voltage VS at the fourth second from the detection of the blow, and the fourth second. It is determined whether the sensor voltage VS is within ± 20% of the sensor voltage VS at the third second (step ST22).

  If the sensor voltage VS at 4 seconds is within ± 20% of the sensor voltage VS at 3 seconds (YES in step ST22), the microcomputer 7 determines a predetermined blowing time necessary for measuring the gas concentration. (For example, 4 seconds) It is determined that exhalation has been blown, and the gas concentration of the detection target gas is calculated using the sensor voltage VS of the 4th second and the reference data registered in the memory 8, and the gas concentration is calculated on the LCD 6. The result is displayed (step ST23).

  On the other hand, if the sensor voltage VS at the fourth second is not within ± 20% of the sensor voltage VS at the third second (NO in step ST22), the microcomputer 7 expires after 3 seconds have passed since the detection of the blowing. Is determined to have been interrupted (step ST24), and the fact that the interruption of the blowing has been detected is displayed on the LCD 6 after 3 seconds.

  The operation when the detection signal of the thermistor 3 is used for the determination of inhalation of breath is as described above, and the operation when the thermistor 3 is not used for the determination of inhalation of expiration will be described below (NO in step ST14).

  In this case, the microcomputer 7 determines whether to breathe out based on the resistance value of the gas sensitive body 20 (that is, the detection voltage VS). In the microcomputer 7, the transistor Q1 is turned on / off after the heat cleaning is finished, and the energization to the heater electrode 20 is continued, and the gas sensitive body 20 is heated to substantially the same temperature as the heat cleaning period in the measurement period. Is done. Further, the microcomputer 7 outputs a signal for turning on the transistor Q2 from the output port PO3 at a timing when the transistor Q1 is turned off, for example, every 0.1 second, and energizes the gas sensitive body 20 through the load resistor R3. The voltage VS across the gas sensitive body 20 is taken in from the input port PI1 and stored in the memory 8 sequentially. When the heat cleaning period ends, the microcomputer 7 reads the detection voltage VS (t−0.5) of the gas sensitive body 20 0.5 seconds before from the memory 8 and also reads the current detection voltage VS from the input port PI1. (T) is taken in and the change rate dVS of the detection voltage VS is calculated using the following equation (2).

dVS = [VS (t) −VS (t−0.5)] / VS (t−0.5) (2)
Then, the microcomputer 7 determines whether or not the change rate dVS of the detection voltage VS is 40% or more and the state of changing in the same direction continues three times (that is, 0.3 seconds) (step ST26).

  Here, if the change rate dVS of the detection voltage VS is 40% or more and the state of changing in the same direction continues three times (that is, 0.3 seconds) (YES in step ST26), the microcomputer 7 It is determined that blowing has started, and subsequently, it is determined whether or not the change rate dVS of the detection voltage VS is 20% or more and the state of changing in the same direction continues five times (that is, 0.5 seconds). (Step ST27).

  If the change rate dVS is 20% or more and the state of changing in the same direction continues five times (0.5 seconds) (YES in step ST27), the microcomputer 7 continues to blow. Determine and wait for 3 seconds (step ST28). After waiting for 3 seconds, the microcomputer 7 measures the sensor voltage VS at the 3rd second and the sensor voltage VS at the 4th second from the detection of blowing, and the sensor voltage VS at the 4th second is equal to the sensor voltage VS at the 3rd second. It is determined whether it is within ± 20% (step ST22).

  Here, if the sensor voltage VS at the fourth second is within ± 20% of the sensor voltage VS at the third second (YES in step ST22), the microcomputer 7 performs a predetermined injection necessary for measuring the gas concentration. It is determined that exhalation has been blown in for a time (for example, 4 seconds), the gas concentration of the detection target gas is calculated using the sensor voltage VS at the 4th second and the reference data registered in the memory 8, and the gas concentration is displayed on the LCD 6. The calculation result is displayed (step ST23).

  On the other hand, if the sensor voltage VS at the fourth second is not within ± 20% of the sensor voltage VS at the third second (NO in step ST22), the microcomputer 7 expires after 3 seconds have passed since the detection of the blowing. Is determined to have been interrupted (step ST24), and the fact that the interruption of the blowing has been detected is displayed on the LCD 6 after 3 seconds.

  If the determination in step ST26 or step ST27 is not established, the microcomputer 7 determines whether 6 seconds have elapsed from the end of the heat cleaning (step ST29), and if 6 seconds have elapsed, the heat cleaning is performed. It is determined that no breath has been blown even after 6 seconds have elapsed from the end, and a blowing error is displayed on the LCD 6 (step ST25).

  The measurement operation of the present embodiment is as described above. If the ambient temperature at the start of measurement is outside the temperature range set corresponding to the human body temperature, the exhalation is blown based on the temperature detected by the thermistor 3. Deciding. In this embodiment, when the exhalation is blown from the exhalation inlet, the detection temperature of the thermistor 3 changes in a direction approaching the exhalation temperature, and the differential output of the detection signal of the thermistor 3 exceeds the inhalation determination value. When the differential output falls below the interruption determination value during the period from the time of the determination to the elapse of the predetermined period of time until the predetermined period of time elapses, it is determined that the injection has been interrupted. Compared with the case where the exhalation of breath is detected from the change in the resistance value, it is possible to start the measurement of the gas concentration by reliably determining the start of exhalation or the interruption of the exhalation.

  In addition, when the ambient temperature is within a temperature range set corresponding to the human body temperature, there is a risk of erroneous detection if breathing in is determined using the detection signal of the thermistor 3, but in the present embodiment, at the start of measurement. If the detected temperature is within the above temperature range, the microcomputer 7 determines the inhalation of the exhalation from the change in the resistance value of the gas sensitive body 20, so that the possibility of erroneously detecting the exhalation of the exhalation can be reduced.

  Furthermore, when detecting the interruption of the blowing, the microcomputer 7 detects the interruption of the blowing because not only the differential output of the detection signal of the thermistor 3 but also the resistance value of the gas sensitive body 20 changes in the low concentration direction. Therefore, it is possible to detect the interruption of blowing more accurately.

  Further, when the heater voltage is detected from the voltage of a pair of energization terminals (the first pin and the fifth pin of the connector CN2) through which the heater current for driving the heater electrode 21 flows, the contact resistance of the board-to-board connectors CN1 and CN2 Since the detection includes the voltage drop, the detection of the heater voltage is inaccurate. However, in this embodiment, the voltage measurement terminal (connector CN2 No. 2) where the drive current of the heater (heater combined electrode 21) does not flow is used. Since the heater voltage is measured from the voltage between the terminals of the pin No. 4 and No. 4 pin), the heater voltage can be measured accurately, and the microcomputer 7 and the heater drive circuit 5 can accurately determine the heat generation amount of the heater, that is, the temperature of the gas sensitive body 20 Therefore, the gas concentration can be measured accurately.

  By the way, the temperature sensing part of the thermistor 3 is disposed in the narrow hole 40b of the exhalation flow path 40 at a location close to the exhaust port 36a. Since the exhaled air blown into the mouthpiece 37 passes through the exhalation flow path 40 and is discharged to the outside from the exhaust port 36a, the exhalation contacts the temperature sensing part of the thermistor 3 disposed in the exhalation flow path 40, The output of the thermistor 3 changes according to the expiration temperature. Here, when the distance from the exhaust port 36a to the temperature sensing part of the thermistor 3 is long, the output of the thermistor 3 may be delayed from returning to the ambient temperature due to the influence of the breath remaining around the temperature sensing part. Therefore, when measurement is continuously performed, the change in the output of the thermistor 3 becomes small, and it becomes difficult to detect the start of blowing exhalation and the interruption of the blowing from the change in the output of the thermistor 3. In the present embodiment, since the thermistor 3 is disposed in the narrow hole 40b of the expiratory flow path 40 at a location close to the exhaust port 36a, after the expiratory blowing is finished, the temperature sensing portion of the thermistor 3 is The exhaled air staying around is easily discharged from the exhaust port 36a in a short time, and the output of the thermistor 3 is easily returned to the output corresponding to the ambient temperature in a short time.

  Therefore, even when exhalation is continuously measured, the output change of the thermistor 3 can be increased, and it is easy to detect the start of exhalation and the interruption of the inhalation from the output change of the thermistor 3. As the thermistor 3, it is preferable to use a thermistor that responds quickly. When the thermal time constant is 5 seconds or more, the sensitivity for spraying detection or interruption detection cannot be obtained, but the thermal time constant is about 2 seconds. By using the thermistor 3, it was possible to obtain sufficient sensitivity for spray detection and interruption detection.

  In the present embodiment, the temperature sensing part of the thermistor 3 is arranged in the small diameter hole 40b slightly closer to the exhaust port 36a than the intermediate position, but the temperature sensing part of the thermistor 3 is arranged as close to the exhaust port 36a as possible. Preferably, the temperature sensitive part of the thermistor 3 may be arranged near the outlet of the exhaust port 36a. However, if the temperature sensing part of the thermistor 3 is arranged near the outlet of the exhaust port 36a, foreign matter may come into contact with the thermistor 3 and the thermistor 3 may be damaged. In the present embodiment, the small-diameter hole 40b Inside, the temperature sensing part of the thermistor 3 is arranged at a position close to the exhaust port 36a. For example, in this embodiment, the inner diameter of the small-diameter hole 40b is 3 mm, and the temperature sensing part of the thermistor 3 is disposed at a position of about 2 mm from the rear surface of the sensor block 34.

  By the way, in said embodiment, although embodiment which applied the technical idea of this invention to the breath breath measuring device was described, it is not the thing of the meaning which limits the breath component of detection object to breath breath factor gas, For example, it is contained in breath The present invention may be applied to an alcohol checker that detects an alcohol component, or may be applied to a device that detects various breath components other than alcohol.

  In this embodiment, instead of the thermistor 3 for detecting the temperature of exhalation, a pressure sensor for detecting the pressure of the flow path through which exhalation flows when exhalation is blown is provided, and the detection output of the pressure sensor is sent to the differentiation circuit 4. It is also conceivable to input the differential output to the microcomputer 7 and detect the state of exhaled breath from the differential value of the detected pressure instead of the differential value of the detected temperature.

DESCRIPTION OF SYMBOLS 1 Battery power supply 2 Gas sensor 3 Thermistor 4 Differentiation circuit 5 Heater drive circuit 6 LCD
7 Microcomputer 8 Memory 10a Sensor board 10b Main board 20 Gas sensitive body 21 Heater combined electrode 22 Detection electrode

Claims (4)

A measuring instrument body provided with an exhalation flow path for passing exhaled air blown from the blow-in opening, and an exhaust port for exhausting exhaled air blown into the exhalation flow path to the outside;
At least a part of the exhaled air blown into the exhalation flow path having a gas sensing element formed of a metal oxide semiconductor whose resistance value changes according to the gas concentration of the detection target gas and a heater embedded in the gas sensing element A gas sensor housed inside the main body of the measuring device so that is in contact with the gas sensitive body,
A measurement start switch that generates a measurement start signal when an operation button exposed on the surface of the measuring instrument body is pressed;
When a measurement start signal is input from the measurement start switch, energization of the heater is started, and after performing a heat cleaning of the gas sensitive body for a predetermined waiting time, a heater control unit that provides a measurement period for measuring the gas concentration When,
A temperature sensor housed inside the measuring device main body so that at least a part of the exhaled air that has been blown into the exhalation flow path contacts the temperature sensing part;
A differential output generator for generating a differential output of the detection signal of the temperature sensor;
When the differential output of the differential output generation unit exceeds a predetermined blowing determination value in the measurement period, it is determined that exhalation has been blown, and the differential output is interrupted for a predetermined period from the time of blowing determination until the blowing time elapses. When it falls below the determination value, an insufflation state detector that determines that the exhalation of breath has been interrupted,
In the measurement period, when the insufflation state detection unit detects that the exhalation has been performed for a predetermined insufflation time necessary for measuring the gas concentration, the detection target gas component contained in the exhalation is detected based on the resistance value change of the gas sensor. An exhalation component measuring apparatus comprising a gas concentration measuring unit for measuring a gas concentration.   If the detected temperature of the temperature sensor at the time of inputting the measurement start signal is outside the temperature range set corresponding to human body temperature, the blowing state detection unit is based on the differential output of the differential output generation unit Detecting the state of exhalation and detecting the state of exhalation from the change in the resistance value of the gas sensing element if the temperature detected by the temperature sensor when the measurement start signal is input is within the above temperature range. The exhalation component measuring device according to claim 1.   In the blowing state detection unit, the differential output of the differential output generation unit falls below a predetermined interruption determination value, or the resistance value of the gas sensitive body is between the time of blowing determination and the passage of the blowing time. 2. The breath component measuring apparatus according to claim 1, wherein when the air concentration changes in a low concentration direction, it is determined that breath blowing is interrupted. The gas sensor has a three-terminal structure of a pair of heater electrode terminals electrically connected at both ends of the heater and an output electrode terminal electrically connected at one end to the gas sensitive body,
A sensor substrate on which at least a gas sensor is mounted, and a main body substrate on which circuits of at least the heater control unit and the gas concentration measurement unit are formed,
A board-to-board connector that electrically connects the sensor board to the main board is connected to a pair of heater electrode terminals and connected to a pair of heater electrodes and a pair of heater electrode terminals, respectively. A pair of voltage measurement terminals for measuring the voltage value of each heater electrode terminal, the heater control unit obtains the heater voltage from the voltage between the terminals of the pair of voltage measurement terminals, and the heater voltage is a desired voltage The exhalation component measuring device according to any one of claims 1 to 3, wherein energization to the heater is controlled so as to be a voltage value.

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