JPH0572221A - Air velocity sensor - Google Patents

Abstract

PURPOSE:To obtain an air velocity sensor in an output signal of which an error hardly occurs even when the temperature of air current to be measured changes sharply and which has high responsiveness. CONSTITUTION:This air velocity sensor 10 comprises a base 12, and a thin-film temperature-measuring resistor 14 for a heater and a thin-film temperature- measuring resistor 16 for temperature compensation are formed on the base 12. The thin-film temperature-measuring resistor 14 for the heater and the thin- film temperature-measuring resistor 16 for temperature compensation are formed in the same shape and dimensions and each of them is formed by applying Pt, for instance, on a rectangular alumina base of a thickness 0.15mm, for instance, by laser trimming or etching. On the base 12, moreover, a circuit of fixed temperature method is formed as a is formed as a detecting circuit 18, which is connected to the thin-film temperature-measuring resistor 14 for the heater and the thin-film temperature-measuring resistor 16 for temperature compensation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wind speed sensor, and more particularly to a wind speed sensor such as a thermal wind speed sensor.

[0002]

2. Description of the Related Art As a wind velocity sensor, there is a thermal type wind velocity sensor such as a Pt sensor, which mainly produces heat from a resistance temperature detector and obtains the wind velocity from the heat radiated by an air flow. As the circuit system of the thermal wind sensor, a constant current method in which a constant current is applied to the resistance temperature detector and a constant temperature method in which the temperature of the resistance temperature detector is controlled to be always constant are often used. In particular, from the viewpoint that the response speed can be increased and the number of circuit parts can be reduced,
The constant temperature method is often used.

FIG. 2 is a plan view showing an example of a conventional thermal wind speed sensor. The wind speed sensor 1 includes two temperature sensors 2 and 3. These temperature sensors 2 and 3 are connected to the electronic circuit 5 of the printed circuit board 4. Among these temperature sensors, one of the temperature sensors 2 uses a heater resistance temperature detector as a heater temperature sensor, and has a function of generating heat at a constant temperature and catching a change in heat radiation due to an air flow. The other temperature sensor 3 uses a temperature compensating resistance temperature detector as a temperature compensating sensor and has a function of correcting an error in the measured value of the wind speed due to the temperature change of the air flow.

As the electronic circuit 5 of the wind speed sensor 1, for example, a constant temperature method circuit system as shown in FIG. 3 is used. The temperature sensors 2 and 3 form a bridge circuit together with the resistors 6 and 7. And the outputs of the temperature sensors 2 and 3 are
It is input to the operational amplifier 8. The output side of the operational amplifier 8 is connected to the base of the transistor 9, and the output of the transistor 9 is fed back to the bridge circuit. An electric current is passed through the temperature sensor 2 for the heater, which causes the temperature sensor 2 to heat. When the airflow contacts here, the temperature sensor 2
Is taken away, and the wind speed is measured from the change in the resistance value of the temperature sensor 2. Further, the temperature sensor 3 for temperature compensation measures the temperature of the air, and the error in the wind speed due to the difference in the temperature of the air is corrected. Therefore, the response speed of the wind speed sensor 1 to the change in the wind speed is determined by the thermal responsiveness of the one temperature sensor 2. Temperature sensor 2 to improve thermal response
Is a very thin alumina substrate having a thickness of 0.15 mm. In such a wind speed sensor 1,
The response time of the wind speed sensor 1 to changes in wind speed is about 0.1.
sec. The other temperature sensor 3 is not involved in determining the response time of the wind speed sensor 1 with respect to changes in the wind speed. Therefore, an alumina substrate having a thickness of 0.6 mm, for example, has been conventionally used for the temperature sensor 3.

[0005]

However, in such a wind speed sensor 1, when the temperature of the air flow to be measured changes suddenly, one temperature sensor 2 and the other temperature sensor 3 are used.
Since the response time of and is significantly different, even if the temperature change ends, the phenomenon that the accurate wind speed signal cannot be output occurs for a while. That is, when the temperature of the airflow rises, first, the change in the amount of heat taken by one of the temperature sensors 2 is measured. Then, the other temperature sensor 3 measures the temperature of the air and corrects the error in the wind speed due to the difference in the temperature of the air. Therefore, the wind speed sensor 1 outputs a wind speed signal indicating that the air flow has become small even if there is no change in the air flow. Therefore, in such a wind speed sensor 1, when there is no rapid temperature change of the air flow, the response time is 0.
Although the response is as high as 1 sec, when there is a rapid temperature change in the airflow, the wind speed signal is output with a very large error.

Therefore, a main object of the present invention is to provide a wind speed sensor having a high responsiveness, in which an error does not easily occur in an output signal even if the temperature of the measured airflow changes rapidly.

[0007]

The present invention includes a resistance temperature detector for a heater for measuring the amount of heat taken by an air flow, and a temperature compensation resistance temperature sensor for measuring the temperature of an air flow, The heater resistance temperature detector and the temperature compensation resistance temperature detector are wind speed sensors that are formed in the same shape and size and detect the wind speed by the constant temperature method.

[0008]

Since the resistance temperature detector for the heater and the resistance temperature detector for temperature compensation are formed in the same shape and the same size,
They have the same heat capacity. Therefore, the thermal responsiveness of the resistance temperature detector for heater and that of the resistance temperature detector for temperature compensation become equal.

[0009]

According to the present invention, it is possible to obtain a wind speed sensor having high responsiveness in which an error does not easily occur in the output signal even when the temperature of the air flow to be measured changes suddenly.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

FIG. 1 is an illustrative view showing one embodiment of the present invention. The wind speed sensor 10 includes a substrate 12. On the substrate 12, a heater thin film resistance temperature detector 14 as a heater temperature sensor and a temperature compensation thin film resistance temperature detector 16 as a temperature compensation temperature sensor are formed. The heater thin film resistance temperature detector 14 is formed, for example, by laser trimming or etching Pt on a rectangular alumina substrate having a thickness of 0.15 mm. Similarly, the thin film resistance temperature detector 16 for temperature compensation also has a thickness of 0.15 m.
It is formed by laser trimming or etching Pt on a rectangular alumina substrate of m. In this case, the resistance value of the heater thin film resistance temperature detector 14 is, for example, 10Ω, and the temperature compensation thin film resistance temperature detector 16 is, for example, 500Ω. In this embodiment, in particular, a thickness of 0.15 mm, which has been conventionally used for a resistance temperature detector for a heater, is used.
Thin film resistance temperature detector for heater 1
4 and the temperature compensating thin film resistance temperature detector 16 are formed in the same shape and the same size.

Further, a detection circuit 18 is provided on the substrate 12.
Is formed. As the detection circuit 18, a constant temperature circuit as shown in FIG. 3 is formed. Then, the heater thin film resistance temperature detector 14 and the temperature compensation thin film resistance temperature detector 16 are connected to the detection circuit 18.

In this wind speed sensor 10, the thin film resistance temperature detector 14 for a heater is heated and the heat of the thin film resistance temperature detector 14 for a heater is taken away by contact with the air flow. The change in the resistance value of the heater thin film resistance temperature detector 14 due to this temperature change is detected by the detection circuit 1.
Detected by 8. Further, the temperature of the air is measured by the temperature compensating thin film resistance temperature detector 16, and the error in the wind speed measurement due to the temperature of the air is corrected. The signals from the heater thin film resistance temperature detector 14 and the temperature compensation thin film resistance temperature detector 16 are input to the detection circuit 18, and a detection signal corresponding to the wind speed is output. This detection signal is output by the lead 20.
Is input to an external circuit for processing the signal.
Further, the power supply for the wind speed sensor 10 is connected to the detection circuit 18 by the lead 22.

In the wind velocity sensor 10, since the thin film resistance temperature detector 14 for heater and the thin film resistance temperature detector 16 for temperature compensation are formed in the same shape and the same size, their heat capacities are the same. become. Therefore, in this wind speed sensor 10, there is no delay in temperature compensation even with a sudden temperature change of the air flow, and an error in the detection signal with respect to the wind speed can be prevented. Therefore, a highly responsive wind speed sensor can be obtained.
In the wind speed sensor 10 of this embodiment, the response speed is 0.
It becomes 1 sec, and the responsiveness can be greatly improved compared to the conventional one.

As the thin film resistance temperature detector 14 for heater and the thin film resistance temperature detector 16 for temperature compensation, for example, a thickness of 0.
A 6 mm alumina substrate may be used. Even in this case, the heater thin film resistance temperature detector 14 and the temperature compensation thin film resistance temperature detector 16 are formed to have the same shape and the same size. When a thick alumina substrate is used for the heater thin film resistance temperature detector 14 and the temperature compensation thin film resistance temperature detector 16, the thermal response is inferior to that using a thin alumina substrate, but the heat capacities are equal. There is no difference in thermal response. Therefore, even with such a wind speed sensor 10, even if the temperature of the air flow changes, there is no delay in temperature compensation for the detection of the wind speed, and an error in the detection signal corresponding to the wind speed can be prevented. The wind speed sensor 10 does not require a thin alumina substrate, so that the cost can be reduced.
Therefore, such a wind speed sensor 10 is used as a low-cost type that does not require much responsiveness.

[Brief description of drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention.

FIG. 2 is an illustrative view showing an example of a conventional wind speed sensor.

FIG. 3 is a circuit diagram of the wind speed sensor shown in FIG.

[Explanation of symbols]

 10 Wind speed sensor 12 Substrate 14 Thin film resistance temperature detector for heater 16 Thin film resistance temperature detector for temperature compensation 18 Detection circuit

Claims (1)

[Claims] 1. A resistance temperature detector for a heater for measuring an amount of heat taken by an air flow, and a temperature compensation resistance temperature sensor for measuring a temperature of the air flow, wherein the resistance temperature detector for a heater is: The temperature compensating temperature-measuring resistor is a wind speed sensor that has the same shape and size and detects the wind speed by the constant temperature method.