JPH0415534A - Pressure measuring instrument - Google Patents

Abstract

PURPOSE:To omit the parts required for connecting a pressure sensor to an enclosed chamber and to curtail the manhour for installing the sensor by fixing a distortion detecting element to the outside wall surface of the enclosed chamber, and detecting the pressure in the enclosed chamber as a distortion of the outside wall. CONSTITUTION:A pressure controller 1 is connected to an enclosed chamber 5. To the outside of the outside wall surface 6 of the enclosed chamber 5, a distortion detecting sensor 2 is fixed, its signal is connected to a sensor circuit 3, and a sensor signal processed by the sensor circuit 3 is connected to an A/D port of a microcomputer 4. Also, the microcomputer 4 is connected to a commercial power source 9 through a low voltage transformer 8 and a constant-voltage generating circuit 7. In such a way, such parts as a screw part for fixing airtightly the pressure sensor, and a connector, etc., become unnecessary, the manhour for assembly is curtailed, and also, the sensor is isolated from an atmosphere in the enclosed chamber and not contaminated, therefore, the durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pressure measuring device using strain sensing elements.

Prior Art Conventionally, this type of pressure measuring device is shown in Fig. 2.
− It had a similar structure. As shown in the figure, the sealed chamber 18 is provided with a pressure reducing device 14 and a pressure sensor 16. The pressure sensor 15 is connected to a threaded portion 19 of the sealed chamber through a threaded portion 2o, and converts the pressure within the sealed chamber 18 into an electrical signal. This electric signal is transmitted to the microcomputer 16 via the connectors 21 and 22, converted into a digital signal, and transmitted to the control section 17, where pressure display and pressure control are performed.

Problems to be Solved by the Invention In such a conventional configuration, the pressure sensor 16 must be fixed to the sealed chamber 18 while maintaining airtightness. For example, a threaded portion 19.20 is provided at the connection portion of both the pressure sensor 15 and the sealed chamber 18, and the threaded portion 19.20 is provided while maintaining airtightness.
The pressure sensor 15 is fixed in the sealed chamber 18 by tightening.

Furthermore, the sensor 15 and the sensor circuit must be connected in an overlapping manner via the connectors 21, 22.

In addition, in this way, the pressure sensitive part of the sensor 16 is connected to the closed chamber 18.
Since the sensor 15 comes into direct contact with the internal atmosphere, the pressure sensitive part of the sensor 15 becomes contaminated, making it difficult to maintain constant pressure accuracy for a long period of time.

The present invention solves these problems by omitting the parts necessary to connect the pressure sensor to a sealed chamber, reducing the number of man-hours required for installing the sensor, and preventing contamination of the pressure sensor so that it can be used for a long period of time. It is an object of the present invention to provide a pressure measuring device that can maintain pressure measurement accuracy.

Means for Solving the Problems In order to solve the problems, the present invention includes a sealed chamber, a strain detection element, means for driving and signal processing of the strain detection element, and pressurizing or depressurizing the sealed chamber. It includes a pressure control device and a control unit that controls the strain detection element and the pressure control device, the strain detection device is fixed to the outer wall surface of the sealed chamber, and the pressure control device pressurizes or depressurizes the sealed chamber. When [) IJ the pressure inside the sealed chamber is detected as a strain on the outer wall by the strain detection element,
The control unit measures the change in pressure.

Function: With this configuration, the pressure inside the sealed chamber can be measured by fixing the strain sensing element to the outside of the wall of the sealed chamber. There is no need for processing. As a result, the number of connecting parts becomes unnecessary, and the process of connection processing can also be reduced.

Furthermore, since the strain detection element is fixed to the outside of the wall of the sealed chamber, it does not come into contact with the atmosphere inside the sealed chamber when measuring pressure. As a result, the strain detection elements are not contaminated by gas or oil smoke existing in the sealed chamber, and pressure measurement accuracy is maintained over a long period of time.

EXAMPLE Hereinafter, a pressure measuring device according to an example of the present invention will be explained with reference to the drawings.

FIG. 1 shows a block diagram of a pressure measuring device. As shown in the figure, a pressure control device 1 is connected to the sealed chamber 6. A strain detection sensor 2 is fixed to the outside of the outer wall surface 6 of the sealed chamber 6,
The sensor signal 51 is connected to the sensor circuit 3 and processed by the sensor circuit 3.

is a microcomputer (hereinafter referred to as microcomputer) 4 A
/Connected to D port. Also, the microcomputer 4 is connected to the commercial power supply 9.
is connected to via a low voltage transformer 8 and a constant voltage generating circuit 7.

FIG. 2 shows a schematic configuration of the strain extrusion element. The substrate 10 is usually a thin plate made of an electrical insulator. A metal wire resistance wire 11 is provided on the surface of the substrate 1o, and a lead wire 12 is connected to the metal resistance wire 11. The method of fixing the substrate 10 to the outer wall 6 of the sealed chamber 5 is as shown in Table 1.
An adhesive suitable for the material of the substrate 10 may be selected and used, and the adhesive may be bonded.

6 ・＼−7 Operation of strain detection element 2, that is, “physical phenomenon” − “
The operation as a converter from "mechanical strain" to "electrical signal" is shown in FIG. The resistance value of the metal resistance wire 11 in Fig. 2 is R
1, R1=ρIV,/a. Here, 2 is the length of the metal resistance wire, a is the cross-sectional layer, and ρ is the specific resistance. Now, when the metal resistance wire is pulled in the axial direction by an external force, the length of the metal resistance wire increases by 7℃, the cross-sectional area decreases by Δa, and the specific resistance decreases by Δρ, then the rate of change in resistance is ΔR/R−Δfl / R-A a / a+Δρ/ρ
・・・・・・・・・・・・＜1), and the strain ε is ε=Δp,/2 ・・・・・・・・・・・・
・・・・・・(Takumi) Also, if the total volume of the metal resistance wire is ■, then ■2aX flood ・・・・・・・・・・・・・・・
...(3) Also, due to the expansion and contraction of the metal resistance wire, the volume is ΔV/V=Δa/a+Δp, 7x−Δa/a+ε
-=-・-・(4) Also, assuming that the rate of change in volume and the rate of change in specific resistance are the same, Δρ/ρ=ΔV/V=Δa/a×ε...
・・・・・・・・・・・・(Ni) 0), (Ni) From equation (6), ΔR/R= 26 However, in actual strain detection elements, (the assumption of transfer equation does not hold) Because of this, equation (6) is obtained.

ΔR/R= Kε ・・・・・・・・・・・・
(6) In equation (6), K is a constant that depends on the metal resistance wire.

This O-strain detection element (resistance R1) is connected to the circuit shown in FIG. The signal detection method will be described below. In Fig. 4, when the applied voltage of the bridge circuit is set to E,
Output voltage e. is eo-[(R40R11)R3-R2R4]/(R1+
R4/+-R2) (R3+R4).

If R1' is adjusted with the strain detection element 2 adhered to the outer wall 6 of the sealed chamber 5 to obtain R1+R11=R2=R3-R42R, then eo -0 is obtained.

Now, if the strain detection element R1 receives strain and causes a change of R4+ΔR4, then eo:EΔR/(4R+2ΔR) EΔR/(4B
, ) However, R(ΔR.

Here, from equation (6) ΔR=4εR, e○=EKε/4 For example: 2. If ε:lX10 and E=1V, e o :IX2X10/4=O-5
+TI V. If this value is amplified by the operational amplifier 13 and inputted to the A/D port of the microcomputer 4, the pressure in the sealed chamber 5 can be measured.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, (1) By fixing a strain detection element to the outer wall of a sealed chamber and measuring pressure, it is possible to solve the problem as conventionally used. What?
Parts such as screws and connectors that secure the pressure sensor airtight are no longer required. Furthermore, since the assembly man-hour effort is reduced to E 1M11 mg, costs can be reduced.

(2) By fixing the strain detection element to the outside of the outer wall of the sealed chamber, it is isolated from the atmosphere inside the sealed chamber, the sensor is not contaminated, and the durability of the strain detection element is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a pressure measuring device according to an embodiment of the present invention, and FIG. 2 is a perspective view and a block diagram of the same strain detecting element. 1... Pressure control device, 2... Strain detection element, 5... Sealed chamber, 6... Outer wall,
10...Substrate, 11...Metal resistance wire,
12...Lead wire. Name of agent: BU↑Physical engineer Shigetaka Awano and one other person Figure 10-K Plate 11- Kin Tan λ latitude t2- Lead latitude map

Claims (1)

[Claims] A sealed chamber, a strain detection element, means for driving and signal processing of the strain detection element, a pressure control device for changing the pressure in the sealed chamber, and a control section for controlling the strain detection element and the pressure control device. The strain detection element is fixed to the outer wall surface of the sealed chamber, and when the pressure control device pressurizes or depressurizes the sealed chamber, the strain detection element detects the pressure inside the sealed chamber as a strain on the outer wall. and a pressure measuring device that measures pressure changes in the control section.