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.COPYRIGHT: (C)2012,JPO&INPIT【課題】呼気の吹込みを確実に検出して呼気成分の測定が行える呼気成分測定装置を提供する。【解決手段】呼気成分測定装置は、呼気吹込口から吹き込まれた呼気が金属酸化物半導体からなる感ガス体20に接触するように測定器本体内部に収納されたガスセンサ2と、呼気吹込口から吹き込まれた呼気が感温部に接触するように測定器本体内部に収納されたサーミスタ3と、サーミスタ3の検出信号の微分出力を発生する微分回路4と、微分回路4の微分出力に基づいて呼気が正常に吹き込まれたことを検出すると、感ガス体20の抵抗値変化に基づいて呼気中の検知対象ガス成分のガス濃度を測定するマイコン7を備える。マイコン7は、微分回路4の微分出力が所定の吹込判定値を超えると、呼気が吹き込まれたと判定し、吹込判定時から所定の吹込時間が経過するまでの間に微分出力が所定の中断判定値を下回ると、呼気の吹込が中断されたと判断する。【選択図】図1
