JPS58117433A - Pressure measuring device - Google Patents

Abstract

PURPOSE:To secure high accuracy without compensation or calibration and to simplify the structure, by connecting two diaphragm having different effective areas, simultaneously applying the pressure, detecting the displacement, generating a repelling force in the direction for offsetting the displacement by an electromagnetic force generating part, and measuring the pressure based on an exciting current at the time. CONSTITUTION:When the pressure of fluid to be measured is simultaneously applied to the diaphragm 11 and 12 through a connecting port 26, the diaphragm 12 having a large area is forcibly pushed owing to the difference in the effective areas, and a connecting rod 13 is tend to move to the side of the diaphragm 11. Therefore, the displacement is detected by a displacement detecting part 18, and the detected signal is sent to an amplifier 22. The output of the amplifier 22 is given to an electromagnetic coil 21b. The repelling force to the diaphragm 12 is generated in a permanent magnet 21a so as to offset the displacement of the connecting rod 13. The exciting current at this time is read by an ammeter in a reading part 24, and the pressure of the fluid to be measured is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a force balance type pressure measuring device.

As an example of a device for measuring the pressure of gas or liquid, as shown in Figures 1 and 2, a combination of a diaphragm and a spring is used to balance the received pressure and spring force, and the amount of displacement of the spring at that time is measured. The most common types are those that read the information electrically or those that are semiconductor type. That is, in Figure 1', (1)
is a diaphragm, (2) is a spring, (3) is an iron core connected to diaphragm (1), (4) is a fixed coil provided on the outer periphery of iron core (3), and (5) is fixed to iron core (3). It is a differential transformer consisting of a coil (4), and has a low pressure inlet (6a) and a high pressure inlet (6b) on both sides of the diaphragm (1).
), the amount of displacement of the iron core (3) is detected by a differential transformer (51), and this is electrically processed and read by a conversion circuit (7). , (8) is a diaphragm, and (9) is a semiconductor pressure sensor in which a pressure-sensitive resistance element consisting of a diffusion layer exhibiting a piezoresistance effect is provided on a silicon substrate, and a bridge circuit is constructed using the pressure-sensitive resistance element. Then, the displacement of the diaphragm (8) due to the pressure applied to the process connection port [alpha] is transmitted to the semiconductor pressure sensor (9), and the change in resistance value of the pressure-sensitive resistance element is electrically processed and read. however,
The one shown in Figure 1 basically includes errors due to temperature changes in the elastic coefficients of the spring and diaphragm, and the one shown in Figure 2 shows that the characteristics of the silicon that constitutes the pressure sensitive part are temperature dependent. In addition, the relationship between pressure and electrical output is non-linear, so compensation and calibration require sophisticated technology. Practical accuracy is considered to be approximately ±0.5% full scale, and it has been difficult to obtain a highly accurate measuring device.

The present invention was made by focusing on these problems, and it is possible to connect two diaphragms with different effective areas by arranging them facing each other and applying pressure to the two diaphragms at the same time. Displacement is detected and the excitation current of the electromagnetic force generating section that generates a repulsive force in the direction of eliminating the displacement is read as a pressure value. In other words, most of the methods that have been widely used in the past have been based on the deviation method, but this method has been improved in terms of maintaining accuracy through compensation and calibration techniques, and in principle can be considered as a force balance method. By adopting this method, we have provided a pressure measuring device that does not require compensation or calibration, or requires little compensation, and is easy to achieve accuracy. This can be obtained using a device with a simple configuration.

Next, one embodiment of the present invention will be described with reference to FIG. The figure is a schematic diagram showing the configuration of the device, in which O1) O2 are diaphragms with different effective areas arranged to face each other, OJ is a connecting rod connecting the diaphragms α2 side z, and O
4) (151 is the diaphragm (Ill O2 bellows, 06) is the case, and the diaphragm 11υ (12,
The pressure sensitive unit surface is sealed by the bellows (141+15) and the case Q61. The mark is a displacement detection part consisting of a movable part (18a) provided on the connecting rod and a fixed part (18b) provided correspondingly.
For example, a differential transformer is used. Circle is an electromagnetic force generating section consisting of a permanent magnet (21) provided on a connecting rod (13) and an electromagnetic coil (21b) provided corresponding thereto, @ is an amplifier that amplifies the output of the displacement detecting section OgJ, ( 2) is the power supply, (Foundation) is the reading unit consisting of an ammeter, the device is the diaphragm (111117J and bellows α4) (pressure case that covers 151, (4) is the connection port, and the fin is the lead wire. Now, the device to be measured When fluid pressure is simultaneously applied to each diaphragm α1J02 through the connection port (to), the larger area diaphragm (12 side) is pushed strongly due to the difference in effective area, and the connecting rod αJ tries to move toward the diaphragm α2 side. , this displacement is detected by the displacement detector, and the detection signal is sent to the amplifier.The output of the amplifier (■) is sent to the electromagnetic coil (21
b) diaphragm α to the permanent magnet (21@)
It generates a repulsive force towards the second side and operates to eliminate the displacement of the connecting rod αe, so by reading the excitation current at this time with an ammeter in the reading section, the pressure of the fluid to be measured can be determined. Can be done.

Here, the pressure of the fluid to be measured is P, and the diaphragm (2) a
If the effective areas of z are S□ and 82, respectively, then the difference Fd in the pressure applied to each diaphragm is Fd-(S2-8□)P if S2>S□, and since S2 and S□ are constant, Fd is It is proportional to the change in P, and the connecting rod α is displaced as shown by the arrow. On the other hand, the amplifier @ has a sufficiently large sensitivity and is configured so that its output gives the permanent magnetism (211) a repulsive force Fi that opposes Fd. through the coil (21b) to reach an equilibrium point. The repulsive force Fi is the electromagnetic coil (21b)
Since it is proportional to the ampere-turn of pi(1)i ・
・・・・・・・・・・・・・・・ (1) Fd P
・・・・・・・・・・・・・・・ (2) Fd=
Fi・・・・・・・・・・・・・・・ From the relationship in (3), P C/3 ■ ・・・・・・・・・・・・・＋41
Therefore, the pressure P is proportional to the current, and the pressure can be determined by the ammeter connected to the reading section.

The configuration and operation of this embodiment are as described above, and it is a force balance method using electromagnetic force.
'A and the connecting rod stage A are virtually undisplaced, so they are not affected by the spring characteristics (linearity, hysterinth, etc.) of the diaphragm aυa2 and the bellows α41 (15), and the thermoelastic coefficients of the diaphragm etc. due to temperature Changes in diaphragm etc. can be offset by making each diaphragm etc. from the same material, so
In principle, there is no need to perform compensation or calibration, making it easy to obtain high accuracy.Furthermore, since two-wire transmission of control power, etc. is easy, there are fewer restrictions on installation location, and the pressure measurement device has a wide range of applications. is obtained.

In addition, if the effective area ratio of the two diaphragms is made thicker, it is possible to measure minute pressure, and if the inside of the pressure-sensitive unit is evacuated, it is also possible to use it for atmospheric pressure (absolute pressure) measurement. The level H of the liquid can also be measured by submerging the pressure sensitive unit (17) in the liquid as shown in the figure.

Next, an application example of the device of the present invention will be described. The first is to measure the dam water level.Since the dam has a large surface area and even a slight change in water level causes a large change in water volume, highly accurate water level measurement is required.
Generally, an accuracy of about 2000 to 1/3000 is required, and the present invention can fully meet this requirement.

The second is level measurement of elevated water tanks.If a float type level meter is used in an elevated water tank such as a factory water tank, maintenance work will be dangerous and high-altitude work, so measurement on the ground without using a float type is required. is desired.

For example, water depth 5 as shown in Figure 5? FL aquarium ■ 35m
When installed on the stand No. 1), the level meter (support) will have 40
If the head pressure of rrLH20 is applied and the pump is driven so that the water level in the water tank changes within 3rrL, the accuracy of the pump control signal transmission requires at least two devices, and the accuracy of level measurement. is 2cm740m=1/
2000 is required, and the present invention can fully meet this requirement.

The third is level measurement for whiskey blending, and blending requires measurement with an accuracy of 1 to 2 degrees per 3rrL.Currently, workers use a ruler to measure the level, but the present invention According to the above, it can sufficiently meet the required accuracy of 1 to 2 mm/3 m, that is, 1/1500 to 1/3000.

As is clear from the above description, the present invention connects two diaphragms with different effective areas and simultaneously applies pressure.
This method detects the displacement, generates a repulsive force in the direction of the displacement in the magnetic force generator, balances it, and measures the pressure using the excitation current at that time.In principle, it is considered a zero-position method. Therefore, high accuracy can be ensured without compensation or calibration, and a highly accurate pressure measuring device with a simple structure and a wide range of applications can be easily obtained.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a conventional example, FIG. 3 is a schematic view of an embodiment of the present invention, and FIGS. 4 and 5 are views showing an example of the same application. (111021...Diaphragm, (1 row...Connecting rod, (18)...Displacement detection section, f21+...Pack magnetic force generation section, □□□...Reading section. Patent applicant: Kawasaki Representative of Steel Manufacturing Co., Ltd. Patent attorney Aohaku Ao and two others Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) Two diaphragms with different effective areas that are arranged facing each other, connected to each other, and movably held together, and the displacement when the pressure of the fluid to be measured is simultaneously applied to the two diaphragms. a displacement detection section that detects the displacement, an electromagnetic force generation section that applies a repulsive force to the diaphragm in the direction of eliminating displacement according to the detection signal of the displacement detection section, and a reading section t that reads the excitation current of the electromagnetic force generation section as a pressure value. A pressure measuring device characterized by comprising: