# US 2014/0190270 A1 · Gas flow rate measuring apparatus

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- Number: US 2014/0190270 A1
- Document ID: US20140190270A1
- Status: Published application
- Kind: A1
- Application number: 14/240,917
- Filed: 2012-08-16
- Published: 2014-07-10
- Earliest claimed: 2011-09-30
- Assignees: Hitachi Automotive Systems, Ltd.
- Inventors: Kazunori Suzuki; Keiichi Nakada; Ryo Sato
- Web page: https://patentgrep.com/patent/US20140190270A1

## CPC

- G01F 1/64: by measuring electrical currents passing through the fluid flow; measuring electrical potential generated by the fluid flow, e.g. by electrochemical, contact or friction effects (G01F1/58 takes precedence)
- G01F 1/6842: {with means for influencing the fluid flow}
- G01F 1/696: Circuits therefor, e.g. constant-current flow meters
- G01F 1/6965: {comprising means to store calibration data for flow signal calculation or correction}
- G01F 5/00: Measuring a proportion of the volume flow
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME

## Abstract

Gas flow rate measuring apparatus comprising resistive element disposed in a gas flow path, a gas flow rate detection circuit, and a gas temperature detection element or a substrate temperature detection element. The detection circuit detects a current flowing through the resistive element, or a voltage generated in response to the current to output a gas flow rate detection signal in accordance with a flow rate of gas flowing. The apparatus corrects characteristics of the gas flow rate detection signal on the basis of a temperature detection signal obtained from these elements and includes signal conversion means for correcting a characteristic bend displaced by more than a certain fixed amount from target characteristics.

## Claims

### Claim 1

A gas flow rate measuring apparatus including
a gas flow rate detection circuit configured to detect a current flowing through at least one resistive element disposed in a gas flow path or a voltage generated in response to the current to output a gas flow rate detection signal in accordance with a flow rate of gas flowing in the gas flow path, and
a gas temperature detection element for detecting a temperature of the gas in the gas flow path or a substrate temperature detection element for detecting a temperature of a substrate provided in the inside of an integrated circuit,
the gas flow rate measuring apparatus correcting characteristics of the gas flow rate detection signal on a basis of temperature detection signal obtained from the gas temperature detection element or the substrate temperature detection element,
wherein the gas flow rate measuring apparatus comprises signal conversion means for correcting a characteristic bend displaced by more than a certain fixed amount from a target characteristic of the gas flow rate detection signal.

### Claim 2 (depends on 1)

The gas flow rate measuring apparatus according to claim 1, wherein:
where the gas flow rate is represented by Q and a value obtained by zero-span operation of an output characteristic of the gas flow rate detection signal which is a target after correction and an output of the gas flow rate detection signal of the resistive element is represented by ΔY;
where a minimum value of a search region for the characteristic bend is represented by a, a maximum value of the search region for the characteristic bend is represented by b, and a division number between a and b is represented by n; and
where the product of a value obtained by dividing the sum of ΔY and a gradient of Q for individual intervals obtained by the division between a and b and a value ΔYmax when ΔY is highest between a and b or a value ΔYmax when ΔY is lowest between a and b is represented by S,
the signal conversion means searches for a location of the characteristic bend in accordance with a and b, calculates a magnitude of the characteristic bend on the basis of the magnitude of S, and then corrects, when the value of an absolute value |S| of S is equal to or higher than 0.005, the gas flow rate detection signal such that the value of |S| is equal to or lower than 0.055 in accordance with the values of a, b, and S.

### Claim 3 (depends on 2)

The gas flow rate measuring apparatus according to claim 2, wherein the signal conversion means includes:
a first coordinate conversion table for moderating a non-linearity of the gas flow rate detection signal;
a second coordinate conversion table for moderating a non-linearity of the temperature detection signal; and
a correction table for carrying out correction on the basis of a signal obtained by the coordinate conversion.

### Claim 4 (depends on 3)

The gas flow rate measuring apparatus according to claim 3, wherein the first and second coordinate conversion tables are regular-interval tables of an arbitrary division number.

### Claim 5 (depends on 2)

The gas flow rate measuring apparatus according to claim 2, further comprising an integrated circuit that converts an output from the gas flow rate detection circuit and an output signal from the gas temperature detection element into digital signals, and converts into and outputs as analog signals the output signals obtained by correcting the digital signals.

### Claim 6 (depends on 3)

The gas flow rate measuring apparatus according to claim 3, wherein the gas temperature detection signal used for the correction table is a gas temperature signal from the gas temperature detection element.

### Claim 7 (depends on 3)

The gas flow rate measuring apparatus according to claim 3, wherein the gas temperature detection signal used for the correction table is a temperature signal from a substrate temperature sensor provided in the integrated circuit.

### Claim 8 (depends on 2)

The gas flow rate measuring apparatus according to claim 2, wherein the gas flow rate measuring apparatus carries out a correction arithmetic process on the basis of the digital signals input from the gas temperature detection signal, the substrate temperature detection signal from a substrate temperature sensor provided in the integrated circuit, and the gas flow rate detection signal from the gas flow rate detection circuit after individual conversion into digital signals is input.