Provided is a thermal flow meter that can be prevented from being eroded due to adhesion of water or like to a cut end portion of the lead exposed from the mold resin of the circuit package. A thermal flow meter 300 of the present invention is a thermal flow meter having a circuit package 400 formed by mounting a detection element 518 on leads 544 and 545 supported by a support frame 512, sealing with a mold resin, and cutting off the support frame 512, wherein cut end portions 544a and 545a of the leads 544 and 545 exposed from the mold resin of the circuit package 400 by cutting off the support frame 512 is covered by a covering portion 371.

A high-temperature resistance is disposed in an internal passage and has its energization controlled based on an intake-air flow rate in the passage to increase/decrease a heat generation amount. A first low-temperature resistance constitutes a bridge circuit which has its energization state changed according to the heat generation amount of the high-temperature resistance. The first low-temperature resistance varies its resistance value according to intake-air temperature. A second low-temperature resistance is an element, which is not incorporated into the bridge circuit and varies its resistance value according to intake-air temperature to increase/decrease an energization amount. The second low-temperature resistance is provided on a substrate. Another bridge circuit produces an intake air amount detection signal using an electrical signal generated by operation of the high-temperature resistance and the first low-temperature resistance. A digital circuit uses an electrical signal produced by the second low-temperature resistance as an intake temperature detection signal.

A high-temperature resistance is disposed in an internal passage and has its energization controlled based on an intake-air flow rate in the passage to increase/decrease a heat generation amount. A first low-temperature resistance constitutes a bridge circuit which has its energization state changed according to the heat generation amount of the high-temperature resistance. The first low-temperature resistance varies its resistance value according to intake-air temperature. A second low-temperature resistance is an element, which is not incorporated into the bridge circuit and varies its resistance value according to intake-air temperature to increase/decrease an energization amount. The second low-temperature resistance is provided on a substrate. Another bridge circuit produces an intake air amount detection signal using an electrical signal generated by operation of the high-temperature resistance and the first low-temperature resistance. A digital circuit uses an electrical signal produced by the second low-temperature resistance as an intake temperature detection signal.

To obtain a thermal flow meter capable of providing thermal insulation without degrading responsiveness of a temperature detection element. A thermal flow meter 300 of the present invention includes an air flow sensing portion 602 that detects a flow rate by performing heat transfer with a measurement target gas passing through the main passage 124 using a heat transfer surface, a temperature detection element 518 that detects a temperature of the measurement target gas, a circuit package 400 obtained by connecting a processing unit 604 that processes signals of the air flow sensing portion 602 and the temperature detection element 518 to a lead and sealing the processing unit 604 using a first molding resin through a first molding process, and a housing 302 where the circuit package 400 is fixed using a second molding resin through a second molding process, wherein, in the circuit package 400, a thickness of a temperature detecting portion 452 for sealing the temperature detection element 518 is thinner than that of a package body portion 426 for sealing the processing unit 604.

A measuring apparatus including a tubular member, a sensor fixed to an outer peripheral surface of the tubular member, and a circuit board that relays a detection signal from the sensor, the circuit board being fixed to the outer peripheral surface in an area different from an area where the sensor is fixed and being separated from the sensor, and a wire that electrically connects the sensor and the circuit board.

A measuring apparatus including a tubular member, a sensor fixed to an outer peripheral surface of the tubular member, and a circuit board that relays a detection signal from the sensor, the circuit board being fixed to the outer peripheral surface in an area different from an area where the sensor is fixed and being separated from the sensor, and a wire that electrically connects the sensor and the circuit board.

To obtain a thermal flow meter capable of alleviating stress in an axial direction that acts on a lead according to a temperature difference between a proximal end side and a leading end portion side of a measuring portion. An air flow sensing portion 300 according to the present invention includes a bypass passage for flowing a measurement target gas 30 received from a main passage 124, and an air flow sensing portion 602 for measuring a flow rate of the measurement target gas 30 by performing heat transfer with the measurement target gas 30 flowing through the bypass passage via a heat transfer surface, and the thermal flow meter includes a circuit package 400 in which the air flow sensing portion 602 and a lead 514 are sealed by a first resin molding process and a housing 302 forming a part of the bypass passage and fixing the circuit package 400 by a second resin molding process. The lead 514 has an outer lead 412 fixed to the housing 302 and protruding from the circuit package 400, and a bent portion 416 having a bent shape is provided on the outer lead 412.

To obtain a thermal flow meter capable of alleviating stress in an axial direction that acts on a lead according to a temperature difference between a proximal end side and a leading end portion side of a measuring portion. An air flow sensing portion 300 according to the present invention includes a bypass passage for flowing a measurement target gas 30 received from a main passage 124, and an air flow sensing portion 602 for measuring a flow rate of the measurement target gas 30 by performing heat transfer with the measurement target gas 30 flowing through the bypass passage via a heat transfer surface, and the thermal flow meter includes a circuit package 400 in which the air flow sensing portion 602 and a lead 514 are sealed by a first resin molding process and a housing 302 forming a part of the bypass passage and fixing the circuit package 400 by a second resin molding process. The lead 514 has an outer lead 412 fixed to the housing 302 and protruding from the circuit package 400, and a bent portion 416 having a bent shape is provided on the outer lead 412.

To obtain a thermal flow meter capable of providing thermal insulation without degrading responsiveness of a temperature detection element. A thermal flow meter 300 of the present invention includes an air flow sensing portion 602 that detects a flow rate by performing heat transfer with a measurement target gas passing through the main passage 124 using a heat transfer surface, a temperature detection element 518 that detects a temperature of the measurement target gas, a circuit package 400 obtained by connecting a processing unit 604 that processes signals of the air flow sensing portion 602 and the temperature detection element 518 to a lead and sealing the processing unit 604 using a first molding resin through a first molding process, and a housing 302 where the circuit package 400 is fixed using a second molding resin through a second molding process, wherein, in the circuit package 400, a thickness of a temperature detecting portion 452 for sealing the temperature detection element 518 is thinner than that of a package body portion 426 for sealing the processing unit 604.

To obtain a thermal flow meter capable of providing thermal insulation without degrading responsiveness of a temperature detection element. A thermal flow meter 300 of the present invention includes an air flow sensing portion 602 that detects a flow rate by performing heat transfer with a measurement target gas passing through the main passage 124 using a heat transfer surface, a temperature detection element 518 that detects a temperature of the measurement target gas, a circuit package 400 obtained by connecting a processing unit 604 that processes signals of the air flow sensing portion 602 and the temperature detection element 518 to a lead and sealing the processing unit 604 using a first molding resin through a first molding process, and a housing 302 where the circuit package 400 is fixed using a second molding resin through a second molding process, wherein, in the circuit package 400, a thickness of a temperature detecting portion 452 for sealing the temperature detection element 518 is thinner than that of a package body portion 426 for sealing the processing unit 604.