JPH07198519A - Differential pressure / pressure transmitter - Google Patents

Abstract

(57) [Abstract] [Purpose] To adjust the compliance with the movement amount of the barrier diaphragm, minimize the hysteresis, and solve the problems of zero point shift and span shift. A center diaphragm 7 is sandwiched between a pair of bodies 1 and 2 having barrier diaphragms 3 and 4 at both ends. In each of the spaces 10 and 11 defined by each barrier diaphragm and center diaphragm,
The filling liquid 17 is filled and filled. The enclosed liquid is held under pressure and the barrier diaphragm is displaced outward. Then, the barrier diaphragm is moved around a point bulging to the convex side where the compliance with the movement amount is the maximum, and the hysteresis is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure or differential pressure indicating transmitter (hereinafter referred to as a differential pressure / pressure transmitter), and in particular adjusts the filling pressure and amount of the filling liquid filled in each pressure measuring section. Therefore, the present invention relates to a differential pressure / pressure transmitter that solves the problem of hysteresis in the diaphragm.

[0002]

2. Description of the Related Art This type of differential pressure / pressure transmitter measures the pressure and differential pressure of various process fluids in order to obtain, for example, the flow rate of fluid in a pipe and the liquid level in a closed container, and outputs the measurement signal. It is installed at a measurement site or the like to transmit to the controller side, and various types such as a standard type, a flange type, a remote seal type, etc. are conventionally known.

For example, a standard type differential pressure transmitter, which is generally well known as this type of differential pressure / pressure transmitter, is provided with a pair of pressure-measuring barrier diaphragms on both side end faces of a pair of detecting body portions. , These barrier diaphragms form a pair of pressure chambers in which a pressure transmitting fill liquid such as silicon oil is filled, and an inner chamber is formed between both bodies, and these are defined by the center diaphragm into the left and right chambers. , The respective pressure chambers are communicated with each other by the communication passages provided in the detection unit body, and the pressure detection means (pressure sensor) such as a semiconductor pressure sensor is interposed between the enclosed circuits by the left and right communication passages. It is configured to be arranged.

Then, the fluid to be measured on the process side has a high pressure PH and a low pressure PL in a pressure measuring chamber formed in a cover which covers the pressure receiving portion by the barrier diaphragm on both ends of the detecting portion body.
Are applied respectively, the differential pressure (PH
-PL) is transmitted to the pressure detecting means via the pressure transmitting filled liquid in the filled circuit such as the communication passage between the barrier diaphragm and the center diaphragm, whereby the differential pressure between the two measuring fluids is detected, and the measured value The various detection signals according to the above are transmitted to the main device side.

Further, in such a conventional differential pressure / pressure transmitter, the relationship between the differential pressure in the corrugated barrier diaphragm and the volume transfer amount is asymmetrical, as is clear from FIGS. 4 and 5. ing. That is, FIG. 5 shows a case where such a barrier diaphragm a receives a differential pressure in FIG. 4 and the enclosed liquid b is displaced to the convex side or the concave side by moving by a required volume movement amount in the enclosed circuit. P-
In the characteristic curve in the range of + x to −x of the V characteristic, the portion having a large inclination in the characteristic curve has a large hysteresis, and the characteristic on the concave side has a large inclination as compared with the characteristic on the convex side and the hysteresis is large. It is getting bigger.

Here, c in FIG. 4 is a body having a pressure receiving surface portion in which the barrier diaphragm a is provided so as to form a filled liquid filled space. Further, in the P-V characteristic in FIG. 5, the range that can be detected by the differential pressure / pressure transmitter is + x to −.
The absolute values are the same between x, and the inclinations on the + side (convex side) are smaller than those on the − side (concave side).

[0007]

By the way, in the above-mentioned differential pressure / pressure transmitter, for example, the actual open shovel 61-502 is used.
In the flange type as shown in Japanese Patent No. 41, etc.,
The amount of the filled liquid on the PH side was larger than that on the PL side, and the barrier diaphragm on the PH side moved more than the PL side due to the change in the amount of the filled liquid depending on the temperature.

The above-mentioned PH-side barrier diaphragm is generally set to be flat when the differential pressure is "0" at 25 ° C., and the temperature is 25 ° C.
In the following cases, there is a problem in that the hysteresis becomes large because the portion having a large inclination in FIG. 5 is used. Also, in such a case, zero shift,
There was also the problem that the span shift was large.

Such a problem occurs not only in the above-mentioned flange type, but also in a standard type differential pressure / pressure transmitter in which left and right filled liquid amounts are substantially equal. That is, it is desired to take some measures to eliminate the problem of hysteresis in the barrier diaphragm, the zero point shift, and the large shift of the span shift.

The present invention has been made in view of the above circumstances, and the enclosed liquid is centered around the point where the barrier diaphragm has the maximum compliance and is the softest in the entire operating temperature and pressure range. The purpose is to obtain a differential pressure / pressure transmitter that can eliminate the hysteresis problem, zero point shift, and span shift problem by adjusting with.

[0011]

In order to meet the above-mentioned requirements, a pressure / differential pressure transmitter according to the present invention is provided with a center diaphragm sandwiched between a pair of bodies having barrier diaphragms at both ends, and When filling and filling the respective spaces defined by the barrier diaphragm and the center diaphragm with the filling liquid, the filling liquid is held in a pressurized state and the barrier diaphragm is displaced outward.

[0012]

According to the present invention, in the wavy barrier diaphragm of the differential pressure / pressure transmitter, the point where the compliance is maximum and the softest with respect to the amount of movement is that it bulges to the convex side. In view of the above, the hysteresis due to the diaphragm can be minimized by adjusting the filled liquid so that the diaphragm moves around that point in the range of the total temperature and the total pressure.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a differential pressure / pressure transmitter according to the present invention. In FIG. 1, first, a detector in a differential pressure transmitter used for measuring this type of differential pressure is used. The schematic configuration of will be briefly described.

That is, reference numerals 1 and 2 in the figure denote a pair of left and right bodies forming a detector body, and the back plate surfaces 1a and 2a formed on the outer surfaces of the left and right bodies have a substantially corrugated disk-like high pressure. Side and low pressure side barrier diaphragms 3, 4 are mounted. In addition, each back plate surface 1
Each of a and 2a is formed in a circular shape having a corrugated cross section of substantially the same shape as the barrier diaphragms 3 and 4, and pressure measuring chambers 5 and 6 are formed between the barrier diaphragms 3 and 4. . Further, the high pressure PH on the upstream side of the in-pipe orifice and the low pressure PL on the downstream side are applied to the outer side surfaces of the barrier diaphragms 3 and 4, respectively, as described above.

A body inner chamber is formed on the joint surface between the left and right bodies 1 and 2, and the body inner chamber is formed by a corrugated disc-shaped center diaphragm 7 so as to form a pair of left and right chambers 7a and 7b. And one chamber 7a communicates with the pressure measuring chamber 5 on the high pressure side through through holes 8a and 9a for pressure medium circulation and also communicates with a sealed circuit 10, and the other chamber 7b communicates with the low pressure side. To the pressure measuring chamber 6 via the through holes 8b and 9b and also to the sealed circuit 11.

The left and right bodies 1 and 2 have inner cylinders 1 made of stainless steel or the like at the upper ends of their outer peripheral portions.
A header 12 composed of 2a and an outer cylinder 12b is arranged, and a sensor section 13 is arranged inside thereof. This sensor unit 13
Is a conventionally known semiconductor pressure sensor 14 for partitioning the enclosed circuits 10 and 11, and a protector 1 for protecting the pressure sensor 14 and sealing the open ends of the inner cylinder 12a and the outer cylinder 12b.
It is composed of 5 and.

In this case, the enclosed circuit 10 on the high voltage side is the inner cylinder 1
High pressure PH is applied to the surface side of the pressure-sensitive sensor 14 in communication with the inside of 2a. In addition, the low pressure side sealed circuit 11 includes an inner cylinder 12
The low pressure PL is communicated to a passage formed in the protective body 15 or the like through a gap passage 16 between the a and the outer cylinder 12b.
4 is given to the inner surface. Then, silicone oil or the like is provided in the conduction path between the pressure measuring chambers 5 and 6 through the through holes 8a and 9a; 8b and 9b and the enclosed circuits 10 and 11 to the high pressure side and the low pressure side of the pressure sensitive sensor 14. The filled liquids 17 are filled as pressure transmitting media. Reference numeral 18 in the drawing denotes a throttle member provided in the through hole and the communication path for the high pressure side and low pressure side pressure fluids.

In the differential pressure transmitter having such a structure, when high pressure PH and low pressure PL are applied to the barrier diaphragms 3 and 4 from the process side, the differential pressure (PH-PL) at this time is detected by the semiconductor. Since it is added to the pressure sensor 14, the sensor 14 is deformed according to the differential pressure, and the amount of deformation is electrically taken out, amplified by an amplifier (not shown), and then displayed on a meter or the like, or transmitted remotely. It

According to the present invention, the center diaphragm 7 is held between the pair of bodies 1 and 2 having the barrier diaphragms 3 and 4 at both ends in the detecting portion of the differential pressure / pressure transmitter as described above. And the respective spaces defined by the barrier diaphragms 3 and 4 and the center diaphragm 7 (pressure measuring chambers 5 and 6, through holes 8a and 8b; 9).
a, 9b, left and right chambers 7a; 7b, a space defined by the enclosing circuit 10; 11, etc.
As is clear from FIG. 1 and FIG. 2, the enclosed liquid 17 is kept under pressure, and each barrier diaphragm 3, 4
Is characterized in that it is in a state of being displaced outward.

Here, these barrier diaphragms 3,
In FIG. 4, the state shown by the solid line in FIGS. 1 and 2 is the expanded state, and the difference from the conventional case shown by the wavy line can be easily understood.

According to this structure, the differential pressure
Barrier diaphragms 3 and 4 that have a wavy shape in a pressure transmitter
In the above, the point where the compliance is maximum with respect to the movement amount and becomes the softest is the point where it bulges to the convex side, and the barrier diaphragms 3 and 4 set that point in the range of total temperature and total pressure. Enclosed liquid 17 to move to the center
By adjusting with, the hysteresis due to the barrier diaphragms 3 and 4 can be minimized.

That is, in such a structure, the barrier diaphragms 3 and 4 are simple in structure.
However, the hysteresis is minimized by adjusting the filled liquid so that the point of maximum compliance and the softest point is the center over the entire operating temperature and pressure range. Can be eliminated.

In other words, according to the present invention, by adjusting the filling amount and the filling state of the filling liquid 17 in the differential pressure / pressure transmitter, the maximum compliance with the moving amount in the wavy barrier diaphragms 3 and 4 can be obtained. It is possible to move around the point that becomes, thereby minimizing the hysteresis, and as a result, it is possible to perform highly accurate measurement. Further, according to the present invention, since the characteristic portion in which the differential pressure change is small with respect to the volumetric movement amount of the enclosed liquid 17 is used, the zero point shift and the span shift can be made small, which allows the differential pressure / pressure transmission. It is possible to exert the effect as a container.

When these advantages are described in detail with reference to FIGS. 2 and 3, the relationship between the differential pressure P at the corrugated barrier diaphragms 3 and 4 and the volume transfer amount V is as shown in FIG. It is asymmetric with respect to the point (0, 0), but is symmetric at the point (V = V0) where the compliance is maximum. Here, in the characteristic curve, the portion with a large slope has a large hysteresis. Therefore, such a portion is not used as much as possible, and it is set so as to move around the point V0 in the entire operating temperature and pressure range. Should be kept to a minimum.

Therefore, according to the present invention, the enclosed liquid 17 is enclosed in the enclosed circuit portion defined by the barrier diaphragms 3 and 4 depending on the pressure applied to the enclosed liquid 17. 4 is filled so that a deformed state of bulging outward can be obtained,
By moving and displacing the center point of the above-mentioned movement, it is possible to minimize the hysteresis as described above.

At this time, as is clear from FIG. 3, the point V
The change in the differential pressure P is smaller when 0 is the center (Δ in the figure).
(See P1 and .DELTA.P0), the change in the slope is also small, and as a result, it is clear that the zero point shift and the span shift are small.

Here, in the differential pressure / pressure transmitter, conventionally, the amount of filled liquid on the PL side is 1566 mm ³ , the amount of filled liquid on the PH side is 1911 mm ³ , and the expansion amount is 42.
0 mm ³ and the pressure of the enclosed liquid is 4.20 × 10 ³ (P
On the other hand, in the present invention, in the case of swelling to the stable point (the experimental value is 460 mm ³ ), the amount of filled liquid on the PL side is 1606 mm ³ , and the amount of filled liquid on the PH side is 1951.
A mm ^3, it may inflated amount 460 mm ³ a and the pressure of the sealed fluid is a 4.60 × 10 ³ (Pa) have been confirmed experimentally.

The present invention is not limited to the structure of the above-described embodiment, but the shape, structure, etc. of each part of the differential pressure or pressure transmitter may be changed.
It is possible to freely change and change it appropriately, and various modifications can be considered. Further, the type of the differential pressure / pressure transmitter suitable for applying the present invention is not limited to the standard type as in the embodiment, and the effect can be exerted even if it is applied to the flange type, the remote seal type and the like. It will be easy to understand.

[0029]

As described above, the differential pressure according to the present invention
According to the pressure transmitter, a center diaphragm is sandwiched between a pair of bodies having barrier diaphragms at both ends, and each space defined by the barrier diaphragm and the center diaphragm is filled with the filling liquid. , Since this filled liquid is kept under pressure and the barrier diaphragm is displaced to the outside, the barrier diaphragm has a simple structure, but it has a compliance in the entire operating temperature and pressure range. By adjusting the filled liquid so that the maximum point and the softest point are centered, the hysteresis is minimized, and it is possible to solve the problems of zero point shift and span shift.

In other words, according to the present invention, in the wavy barrier diaphragm in the differential pressure / pressure transmitter, the point where the compliance is maximum and the softest with respect to the moving amount bulges on the convex side. In view of that,
By adjusting the filled liquid so that the diaphragm moves around that point in the range of total temperature and pressure, the hysteresis due to the diaphragm can be minimized. As an excellent effect.

That is, since the hysteresis can be reduced as described above, highly accurate measurement is possible. Further, since the characteristic portion having a small differential pressure change with respect to the volumetric movement amount of the enclosed liquid is used, the zero point shift and the span shift can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part showing a structure of a detecting part, which is an essential part of an embodiment of a differential pressure / pressure transmitter according to the present invention.

FIG. 2 is a schematic view of a barrier diaphragm portion for explaining the function and effect of the differential pressure / pressure transmitter according to the present invention.

FIG. 3 is a characteristic diagram showing a use range according to the present invention in a PV characteristic of a barrier diaphragm.

FIG. 4 is a schematic view of a conventional barrier diaphragm portion.

FIG. 5 is a characteristic diagram showing a conventional range of use in the P-V characteristic of a barrier diaphragm.

[Explanation of symbols]

 1 Detection Body 1a Back Plate Surface 2 Detection Body 2a Back Plate Surface 3 Wavy Barrier Diaphragm 4 Wavy Barrier Diaphragm 5 Pressure Measuring Chamber 6 Pressure Measuring Chamber 7 Center Diaphragm 8a Pressure Medium Flow Through Hole 9a Pressure Medium Flow Through Hole 10 Enclosed circuit 11 Enclosed circuit 12 Header 13 Sensor part 14 Semiconductor pressure sensor

Claims (1)

[Claims] 1. A differential pressure in which a center diaphragm is sandwiched between a pair of bodies having barrier diaphragms at both ends, and each space defined by the barrier diaphragm and the center diaphragm is filled with an enclosed liquid. In the pressure transmitter, the filled liquid is held in a pressurized state, and the barrier diaphragm is displaced outward.