Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2001-02-13
2003-12-09
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C073S204180, C073S204260, C374S030000, C392S470000, C422S051000, C422S052000, C702S113000
Reexamination Certificate
active
06662121
ABSTRACT:
TECHNICAL FIELD
This invention relates to a thermal fluid sensor which can be used to discriminate the kind of fluid, a fluid identifying apparatus and method for identifying the kind of an object fluid for measurement (simply referred to as object fluid or fluid) on the basis of a temperature detected signal produced from the fluid sensor, a flow velocity sensor (simply referred to as a flow sensor) which can be used for measurement of the flow rate, and a flow rate measuring apparatus and method for measuring the flow rate of the object fluid on the basis of a temperature detected signal. More particularly, this invention relates to a flow sensor and a flow rate measuring apparatus and method which can measure the flow rate of the fluid accurately even when the kind and composition of the fluid are changed, and relates to a flow rate measuring apparatus and method which can measure the flow rate of the fluid even when the measuring range of the flow rate is relatively wide.
BACKGROUND ART
FIG. 9
shows an arrangement view of a conventional thermal micro-flow sensor. A micro-flow sensor
101
includes an Si substrate
102
, a diaphragm
103
, a micro-heater
104
, a downstream thermopile
105
formed on the diaphragm
103
at the lower end of the micro-heater
104
, power source terminals
106
A,
106
B for supplying a driving current to the micro-heater
104
, an upstream thermopile
108
formed on the diaphragm
103
at the upper end of the micro-heater
104
, first output terminals
109
A,
109
B for producing a first temperature detected signal supplied from the upstream thermopile
108
, and second output terminals
107
A,
107
B for producing a second temperature detected signal supplied from the downstream thermopile
105
.
According to the micro-flow sensor
101
thus configured, in response to the driving current supplied externally, the micro-heater
104
heats an object fluid for measurement such as a gas to generate uniform temperature distributions from itself to the downstream thermopile
105
and from itself to the upstream thermopile
108
.
In this state, when the flow from P to Q is generated in the object fluid such the gas, the temperature distribution around the micro-heater is deflected downstream of the object fluid, i.e. toward the downstream thermopile
105
. Therefore, the upstream thermopile
108
detects the temperature lower than when no flow is generated in the fluid, i.e. flow rate=0. Then, the upstream thermopile
108
produces the first temperature detected signal corresponding to the detected temperature.
On the other hand, the downstream thermopile
105
detects the temperature higher than when no flow is generated in the fluid, i.e. flow rate=0 by the degree the temperature distribution has been deflected downstream. Then, the downstream thermopile
105
produces the second temperature detected signal corresponding to the detected temperature. Thus, a flow rate measuring apparatus (not shown) can measure the flow rate of the object fluid on the basis of a difference signal between the first temperature detected signal from the upstream thermopile
108
and the second temperature detected signal from the downstream thermopile
105
.
However, the conventional micro-flow sensor as shown in
FIG. 9
has a disadvantage that when the kind or composition of the object fluid, the output characteristic is also changed.
Specifically, when the kind or composition of the fluid, the physical property (hereinafter simply referred to as “property”) of the fluid such as thermal conductivity, specific heat, viscosity, density, etc. is also changed. This modifies the temperature distribution of the fluid heated by the micro-heater, and hence the output characteristic.
In order to obviate such failure, aside from the micro-flow sensor, a gas analysis sensor was arranged, or otherwise the micro-flow sensor or a device incorporating it was caused to recognize the properties of the fluid previously.
However, for example, in a gas meter, the gas having the same standard has a slightly different composition of the raw gas according to various lots. The gas composition for controlling the quantity of heat is adjusted with limited accuracy by a gas production factory so that the composition of the gas having the same standard may be changed. Therefore, there was a limit for the characteristic value of the fluid to be previously recognized by the micro-flow sensor and the device incorporating it.
Where the gas analysis sensor is arranged aside, the gas meter is upsized, and the method for correcting the flow rate and the location of the gas analysis sensor must be considered. This makes it difficult to manufacture the gas meter at low cost.
DISCLOSURE OF THE INVENTION
This invention has been accomplished in view of the above circumstance.
An object of this invention is to provide a thermal fluid sensor and fluid identifying apparatus and method which permits a flow sensor to measure the flow rate of an object fluid accurately even when the flow sensor produces a change in the output characteristic with a change in the kind or composition of an object fluid, and also provide the flow sensor and flow rate measuring apparatus and method which is preferably used to measure the flow rate using these thermal fluid sensor and fluid identifying apparatus and method.
In order to attain the above objects, the thermal fluid sensor defined in another aspect of the invention is characterized by comprising:
a heater for heating an object fluid for measurement flowing through a flow path by a driving current externally supplied;
a side temperature sensor arranged in a direction orthogonal to the flow direction of the object fluid with respect to the heater to detect the temperature of the object fluid so that a temperature detected signal is produced; and
a supporting board for supporting the heater and the side temperature sensor.
The fluid discriminating apparatus in another aspect of the invention for discriminating the kind of the object fluid using the thermal fluid sensor is further characterized by comprising:
fluid property computing means for computing the property of the object fluid on the basis of the temperature detected signal supplied from the side temperature sensor in the thermal fluid sensor.
The fluid discriminating apparatus in another aspect of the invention for discriminating the kind of the object fluid using the thermal fluid sensor is further characterized by comprising:
flow rate measuring means for measuring the flow rate of the object fluid flowing through the fluid path;
reference range data storage means for storing data of a plurality of kinds of reference ranges of the temperature detected signal corresponding to the flow rates of the object fluid flowing through the flow path, the reference ranges being different according to the kinds of the object fluid and correlated with the kinds;
reference range data inferring means for inferring a single reference range data corresponding to the flow rate of the object fluid from data of the plurality of reference ranges stored in the reference range data storage means;
pertinent reference range determining means for determining the reference range correlated with the object fluid to which the temperature detected signal belongs,
wherein it is determined that the object fluid correlated with the reference range thus determined is the object fluid flowing through the flow path.
The fluid discriminating method in another aspect of the invention of discriminating the object fluid using the thermal fluid sensor is further characterized by comprising:
fluid-property computing step of computing the property of the object fluid on the basis of the temperature detected signal supplied from the side temperature sensor in the thermal fluid sensor.
The fluid discriminating method in another aspect of the invention for discriminating the kind of the object fluid using the thermal fluid sensor, comprises:
flow rate measuring step of measuring the flow rate of the object fluid flowing through the fluid path;
Oda Seiji
Yamaura Michiaki
Armstrong Westerman & Hattori, LLP
Le John
Yazaki -Corporation
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