JPH03277973A - Semiconductor current meter - Google Patents

Abstract

PURPOSE:To reduce in size and weight, to facilitate handling and to decrease a cost by displacing a silicon diaphragm by a force from fluid to be measured, and detecting the displacement by a piezo resistance element. CONSTITUTION:A plurality of piezo resistance elements 2 for detecting the displacement of a silicon diaphragm are so arranged as to form a bridge on the surface of the vicinity of one end of the diaphragm 1, and a flow peeling material 3 is arranged at the end of the vicinity. They are fixedly disposed in the bottom of a tube 5 along the flowing direction of fluid to be measured through a support 4 with the material 3 as the upstream side. A pressure distribution responsive to the flowing speed of the fluid is generated on the pressure receiving surface of the diaphragm by the material 3. Thus, the diaphragm 1 is received by the force from the fluid, the force is detected by the elements 2, and the speed of the fluid can be obtained from the output signals of the elements.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a semiconductor type current meter, and more particularly to a small and easy-to-handle semiconductor type current meter suitable for measuring flow velocity in a pipe.

<Prior Art> Conventionally, a hot wire method, a pitot tube method, etc. have been used to measure the flow velocity in a pipe.

Hot wire anemometers utilize the fact that when a platinum wire heated by an electric current is exposed to a fluid, heat is removed, the temperature drops, and the electrical resistance of the platinum wire decreases.It is mainly used to measure the flow velocity of gases. It is used. Specifically, there is a constant voltage method in which the heating voltage is kept constant and the flow velocity is determined from changes in unbalanced current caused by changes in the resistance value of the platinum wire, and a method in which the heating voltage is kept constant and the flow rate is determined from changes in the unbalanced current caused by changes in the resistance value of the platinum wire. There is a constant temperature method that calculates the flow velocity from the change in current.

On the other hand, a Pitot tube current meter applies Bernoulli's theorem and is used to measure air and water flows. For example, if one end of a pipe with both ends open is bent into an L shape and immersed in a stream of water, with the end facing upstream, the flow is blocked and the dynamic and static pressures of the water flow are applied inside the pipe. The water level in the pipe becomes higher than the water level in the water stream by an amount of dynamic pressure proportional to the flow velocity. Therefore, in the case of water flow, the flow velocity can be measured using only a pitot tube, which is a pipe with both ends open and one end bent into an L-shape. In addition,
When measuring the flow rate (dynamic pressure) of airflow, static pressure tubes for measuring static pressure are combined to determine the differential pressure between the total pressure and the static pressure.

<Problems to be Solved by the Invention> However, all of these conventional current velocity meters have problems in that they are relatively large, are not easy to handle, and are expensive.

The present invention has been made with attention to these points,
The purpose is to provide a semiconductor type current meter that is small, lightweight, easy to handle, and inexpensive.

<Means for Solving the Problems> The present invention for solving the above problems includes: a silicon diaphragm in which a pressure receiving surface is arranged along the flow direction of a fluid to be measured; a piezoresistive element that detects the flow rate of the fluid to be measured; and a flow separation body that is disposed near the upstream end of the silicon diaphragm and generates a pressure distribution on the pressure receiving surface of the silicon diaphragm in accordance with the flow velocity of the fluid to be measured. It is characterized by this.

Effects> According to the semiconductor current meter of the present invention, the silicon diaphragm receives the force from the fluid to be measured and is displaced, and the piezoresistive element detects the displacement.

Thereby, the flow velocity of the fluid to be measured can be determined from the output signal of the piezoresistive element.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a simplified sectional view of FIG. 1, and FIG. 3 is a diagram showing pressure distribution. In the figure, a plurality of piezoresistive elements (gauges) 2 are arranged on the surface near one end of a silicon diaphragm 1 to form a bridge, and the end of the silicon diaphragm 1 near the piezoresistive elements 2 is made of glass, for example. A flow separation body 3 is provided. The silicon diaphragm 1
is formed by, for example, anisotropic etching, and the bottom surface of the tube 5 is etched along the flow direction of the fluid to be measured via a support 4 made of glass, for example, with the flow separation body 3 located on the upstream side. is fixedly placed. Note that the width of this pressure receiving surface is b, and the length is L. The flow separation body 3 and the support body 4 are bonded to the silicon diaphragm 1 by anodic bonding, low melting point glass, or the like. The pressure inside the silicon diaphragm 1 is maintained at a constant value P, such as atmospheric pressure or vacuum.

Depth D of the fluid to be measured in the tube 5 and height H when the flow separation body 3, silicon diaphragm 1 and support body 4 are overlapped
The relationship is made to satisfy H<D.

In such a configuration, the silicon diaphragm 1 receives a force from the fluid to be measured, and the piezoresistive element 2 detects the force, and the flow velocity of the fluid to be measured F can be determined from the output signal of the piezoresistive element 2. I can do it.

A part of the flow of the fluid to be measured is separated from the entire flow at the front corner of the flow separation body 3. The tip of the separated flow moves a certain distance g at a flow velocity V, as shown in FIG. 3(a), and then attaches to the surface of the silicon diaphragm 1. This distance p is proportional to the flow velocity V. That is, i ocv, ,,I-to-v-
The following relationship holds true: (1) (K: constant).

When this embodiment is arranged as shown in FIG. 3(A), the pressure P on the upper surface side of the silicon diaphragm 1. The distribution of is shown in Figure 3 (
The distribution of the pressure P on the side of the silicon diaphragm 1 is constant as shown in FIG. 3(c). Therefore, forces F and F' expressed by the following equations are applied to positions approximately I/2 and I + (t2) from the rear end of the flow separation body 3 of the silicon diaphragm 1, respectively.

F”(Po −P+) ・Db −
(2) F″”lPo −Ko ' (1/2) '
P ” V 2-Pt l・g゛・b = (2・v2 to K+-) b・(L-1)/2-(
3) However, K, , , , : Constant Po : Pressure on the top surface of silicon diaphragm 1 within distance g ρ : Fluid density Due to these forces F and F', piezoresistance near the fixed end of silicon diaphragm 1 A bending moment M and a stress σ based on the bending moment M act on the element 2, and the gauge output E is Eocσ eM cX:F −j+F′ −(14(j′/2)1”1
) 2” (K I − 2 ・V2)・+ o, −j)
/21・((L+1)/2+c1cV2+(Kl−
2-V2) (L2-K)-V2)s”K, 6V4 +
, 6V2 + 6, ', E = 4 ・V' + 5
・6-(4) for V2+ However, K3. 4. ni,,ni6
: Becomes a constant.

That is, the flow velocity V can be determined from the gauge output E. In addition, 4. is added to the constant. 5. Calibrate and find 6 in advance. Further, the height H (including 0) of the flow separation body 3, the length C along the flow direction, etc. are selected to be optimum values.

The current meter configured in this manner is small and easy to handle. Moreover, since it can be mass-produced using a semiconductor manufacturing process, it is inexpensive.

Furthermore, by forming a signal processing circuit on a fixed portion of the silicon diaphragm together with the piezoresistive element, a signal-processed output can be obtained.

<Effects of the Invention> As described above in detail, according to the present invention, it is possible to provide a semiconductor type current meter that is small, lightweight, easy to handle, and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, Figure 2 is a simplified cross-sectional view of Figure 1; FIG. 3 is an explanatory diagram of pressure distribution. 1...Silicon diaphragm 2... Piezoresistive element (gauge) 3...Flow separation body 4...Support No. figure No. figure 2 vinyl V 砿织碇士HOGOON J No. figure

Claims (1)

[Scope of Claims] A silicon diaphragm whose pressure-receiving surface is arranged along the flow direction of a fluid to be measured; a piezoresistive element disposed on the silicon diaphragm to detect displacement of the silicon diaphragm; and the silicon diaphragm. a flow separator disposed near the upstream end of the silicon diaphragm to generate a pressure distribution on the pressure receiving surface of the silicon diaphragm according to the flow velocity of the fluid to be measured.