KR100946255B1 - Apparatus for measuring water pressure in differential form - Google Patents

Abstract

The present invention discloses a differential underwater pressure measuring device. According to the present invention, the first sensor for measuring pressure and the second sensor for compensating for error are installed in the pressure measuring device with the same specification, so that the error occurring in the sensor itself is canceled with each other due to external environmental change or passage of time. By using the low cost sensor, accurate measurement is possible. In addition, the present invention by applying a pressure similar to the pressure of the actual measurement point in advance to the sensor for error compensation to set the initial value of the sensor measurement value, it is possible to naturally cancel the effect of the period drift that occurs during long-term use under pressure It has an effect.

Description

Apparatus for measuring water pressure in differential form

The present invention relates to an underwater pressure measuring device, and more particularly, to a pressure measuring device capable of measuring a water pressure by arranging a pressure sensor in a differential type.

Tsunami is a phenomenon in which the surface of the sea water rises to damage the coastal environment, in the present invention refers to the height of the surface of the sea water, more precisely the height of the water column at a specific point. There are two methods of measuring the height of the tsunami, that is, the surface of the sea, are the direct method of measuring the height of the water column and the indirect method of measuring the underwater pressure.

The direct method is to set up an altitude station, set up a scale, read it with a telescope, or float a buoy to measure altitude with a precise GPS. It is difficult to do and expensive to measure.

Therefore, tsunami in the ocean is usually measured by indirect hydraulic pressure measurement. However, in order to accurately measure the water pressure, an accurate pressure sensor should be used, and since the accurate pressure sensor is very expensive, it is difficult to apply universally. Existing accurate pressure sensor is a pressure sensor that measures the frequency of the quartz crystal and measures the temperature of the sensor separately to compensate for the pressure, the price is about 50 to 100 times higher than the semiconductor pressure sensor to be applied to the present invention.

As described above, the existing direct measurement methods or indirect measurement methods have been difficult to obtain tsunami data by installing at many points over a large sea area due to cost and environmental problems.

The problem to be solved by the present invention is to provide a pressure measuring device that can accurately measure the pressure of the liquid by using a low-cost pressure sensor that can be used in general.

In particular, the problem to be solved by the present invention is to provide an underwater pressure measuring apparatus capable of measuring the water pressure, such as the height of the tsunami by using a low-cost semiconductor pressure sensor mass-produced in recent years industrial.

Underwater pressure measuring apparatus of the present invention for achieving the above technical problem, the first sensor unit and the second sensor unit for measuring the difference between the upper pressure and the lower pressure applied to the diaphragm; An upper housing having an upper surface and a lower surface opened and having a first accommodating portion accommodating a first sensor portion therein, and a second accommodating portion with a lower surface open and accommodating a second sensor portion therein; And a lower housing coupled to the upper housing such that the upper surface is opened so that air received therein applies air pressure to the lower portions of the diaphragms of the first and second sensor portions through the lower surfaces of the first and second accommodating portions.

In addition, the above-described underwater pressure measuring apparatus may further include a connecting portion coupled to the through hole and for introducing a pressure measuring liquid between the upper surface of the first receiving portion and the upper surface of the diaphragm of the first sensor portion through a tube inserted therein. have.

In addition, the liquid is filled between the upper surface of the second accommodating portion and the upper surface of the diaphragm of the second sensor portion, the above-described underwater pressure measuring device adjusts the distance between the upper surface of the second accommodating portion and the second sensor portion, the liquid is the second The control unit may further include an adjusting unit for adjusting an initial pressure value applied to the diaphragm.

In addition, the above-described underwater pressure measuring device corrects the measured value of the first sensor part to the measured value and the initial pressure value of the second sensor part, and measures the pressure of the measurement target liquid applied from the outside of the pressure measuring device through the through hole. can do.

In addition, the above-mentioned underwater pressure measuring apparatus can measure the pressure of the liquid applied from the exterior of the pressure measuring apparatus by subtracting a 2nd sensor value from the measured value of a 1st sensor part, adding an initial pressure value.

In addition, the aforementioned initial pressure value may be obtained by measuring the height of the liquid filled in the tube when the measured value of the first sensor portion and the measured value of the second sensor portion are the same in the state that the liquid to be measured is applied through the tube. .

In addition, the above-described underwater pressure measuring device is submerged in water, it is possible to measure the water pressure applied from the water surface to the pressure measuring device.

According to the present invention, the first sensor for measuring pressure and the second sensor for compensating for error are installed in the pressure measuring device with the same specification, so that the error occurring in the sensor itself is canceled with each other due to external environmental change or passage of time. By using the low cost sensor, accurate measurement is possible.

In addition, the present invention by applying a pressure similar to the pressure of the actual measurement point in advance to the sensor for error compensation to set the initial value of the sensor measurement value, it is possible to naturally cancel the effect of the period drift that occurs during long-term use under pressure It has an effect.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Prior to describing a preferred embodiment of the present invention, a semiconductor pressure sensor used in the embodiment of the present invention will be described.

The semiconductor pressure sensor is a sensor that has been recently accelerated in practical use. It is characterized by no hysteresis, excellent linearity, and very small and light against vibration. It also has higher sensitivity, higher reliability, and better mass production than mechanical type. It consists of two parts: a diaphragm that converts external pressure into stress and a power that converts the power generated by the diaphragm into an electrical signal.

Diaphragm is formed by chemically etching single crystal silicon, and it converts stress generated from diaphragm into electrical signal by using natural frequency change of oscillator and surface acoustic wave but there are mainly two kinds of piezoresistive type and capacitive type. Is the most used.

Piezoresistive is also referred to as resistance diffusion or diffusion, because the impurity diffusion process of the semiconductor is used to form the resistance element. Piezoresistive pressure sensor is widely used for engine control, industrial measurement, medical, etc. and can be applied to all fields.

The capacitance expression changes the gap between the electrode plates facing each other due to the stress from the outside, thereby changing the capacitance between the electrodes. When the capacitance change is converted into an electrical signal, stress is detected. Using this principle is a capacitive semiconductor pressure sensor. Compared with piezoresistive, capacitive type has high sensitivity, complex electrode formation, and complicated connection with external circuit. However, due to its excellent temperature characteristics, small size, and high sensitivity, it has many advantages when used in the non-pressure area such as a living body.

In addition, the polycrystalline silicon pressure sensor has a strain gage made of a polycrystalline silicon thin film and a diaphragm is formed on the metal to expand the range of the measured pressure. There is also a silicon on sapphire (SOS) pressure sensor that can be used in harsh environments such as high temperatures and corrosive atmospheres. This is a sensor that epitaxially grows a silicon thin film on a sapphire substrate and uses this SOS film as a detection element.

The semiconductor pressure sensor is inexpensive, but has a disadvantage of ① large drift with respect to temperature, ② large internal error of the sensor itself, and ③ long-term drift due to long-term use compared to an accurate quartz crystal pressure sensor.

The semiconductor gauge pressure sensor is difficult to use underwater because the error due to internal pressure is large unless the pressure inside the instrument is piped to the same as atmospheric pressure. The present invention is configured to offset the error using two semiconductor pressure sensors so that the pressure inside the instrument is automatically corrected without exposing the pressure to atmospheric pressure. Here, the error is a drift due to temperature, the internal error of the semiconductor sensor itself, the period drift due to long-term use, etc. In the present invention, these errors are designed to cancel each other.

In the differential pressure measuring apparatus according to the present invention, two identical semiconductor gauge pressure sensors are used for hydraulic pressure measurement and error compensation, respectively, in order to offset the error. The pressure sensor for hydraulic pressure measurement and the pressure sensor for error compensation share their respective vent holes to equally be influenced by the internal air pressure and cancel the error due to the internal air pressure. At this time, the pressure sensor for error compensation is applied in advance to the pressure similar to the water pressure of the measuring point, it is characterized in that the period drift that occurs during long-term use under the pressure is also canceled.

There are two types of pressure sensors: gauge pressure sensors and absolute pressure sensors. Gauge pressure sensors measure the pressure applied to the diaphragm against atmospheric pressure (or ambient air pressure).

1 is a diagram schematically showing a configuration of a general gauge pressure sensor. Referring to FIG. 1, a general gauge pressure sensor has a diaphragm 12 formed at the center of the sensor frame 11, and blocks the flow of air or liquid from the outside when the sensor is installed outside the sensor frame 11. O-ring is installed. In addition, a through hole 14 for transmitting atmospheric pressure to the lower portion of the diaphragm 12 is formed in the lower end of the sensor frame 11, the voltage according to the pressure difference between the pressure of the fluid applied to the diaphragm 12 and the atmospheric pressure (The sensing element of the semiconductor gauge pressure sensor is composed of piezoelectric sensors, but the semiconductor pressure sensor is a structure well known to those skilled in the art, and the features of the present invention are not related to the sensing element, but use a plurality of conventional semiconductor pressure sensors. Since it relates to a pressure measuring device to compensate for the measurement error, the illustration and description of the structure of the sensing element is omitted. These gauge pressure sensors measure pressure against atmospheric pressure, so the output voltage in the atmosphere is zero.

2 is a diagram illustrating an example of measuring water pressure with a semiconductor gauge pressure sensor. Referring to FIG. 2, the conventional pressure measuring apparatus of the present invention to improve the measurement error is mainly installed as shown in FIG. 2 so that the pressure sensor shown in FIG. 1 is accommodated in the housing 20 and disposed in the water. do. The measurement result of the pressure measuring device shown in FIG. 2 is as described in Equation 1 below.

P = P_air + P_water-P_inside

Here, P_air represents the atmospheric pressure, P_water represents the pressure from the water surface to the diaphragm 12, that is, the height of the water column, P_inside represents the air pressure inside the pressure measuring device.

P_water is a value to be measured by using the pressure measuring device shown in FIG. 2, and if P_air and P_inside values are known correctly, P_water value can be measured accurately. By the way, P_air can be measured easily and accurately in the air, and the data is published by the Meteorological Administration, but P_inside changes according to the temperature and characteristics inside the measuring device. Therefore, to accurately measure P_inside, measure the air pressure inside the pressure measuring device. There is a problem in that additional sensors must be installed, and in reality, it is difficult to additionally install such sensors.

3 is a diagram illustrating another example of measuring the water pressure with the semiconductor gauge pressure sensor. The pressure measuring device of FIG. 3 is configured to expose the vent tube 30 to the atmosphere in order to solve the problem of the pressure measuring device of FIG. 2 described above.

In the case of the pressure measuring device shown in FIG. 3, since the internal pressure P_inside of the pressure measuring device is equal to the atmospheric pressure P_air and canceled in the diaphragm, the water pressure P_water to be measured becomes a measurement value of the semiconductor pressure sensor, thus enabling accurate water pressure measurement. Become. In the case of the pressure measuring device shown in FIG. 3, it is almost impossible to maintain the same atmospheric pressure and the pressure inside the measuring device by installing the vent tube 30 in water in an environment such as the ocean where tsunamis may occur. This exists.

4 is a diagram showing an example of a pressure measuring device for measuring water pressure with a semiconductor absolute pressure sensor instead of using the semiconductor gauge pressure sensor shown in FIG. 1.

In the absolute pressure sensor shown in FIG. 4, the diaphragm 42 is installed at the center of the sensor frame 41, and the space between the diaphragm 42 and the sensor frame 41 is vacuumed, so that the internal pressure is zero. . Therefore, the measured value of the absolute pressure sensor is equal to the sum of all the pressures applied to the upper portion of the diaphragm 42, as described in equation (2).

P = P_air + P_water

The use of such an absolute pressure sensor seems to solve the above problems at first glance, but the absolute pressure sensor has a disadvantage that the resolution is worse than that of the gauge pressure sensor because the full scale is wider than the atmospheric pressure.

The gauge pressure sensor has a zero output voltage in the atmosphere, but the absolute pressure sensor outputs an output voltage corresponding to atmospheric pressure in the atmosphere. This corresponds to about 10m of water column height.

For example, if a pressure measuring device for measuring tsunamis is installed at a depth of 5 m, a sensor with a full scale of 10 m is sufficient for a gauge pressure sensor, but a full scale is 10 m larger for an absolute pressure sensor. That is, 20 meters should be. Therefore, in this case, there is a problem that the resolution and accuracy are twice as bad.

In the present invention, since the use of the semiconductor gauge pressure sensor as shown in FIG. 2 is good in terms of resolution and accuracy, the present invention devised a method capable of correcting the air pressure (P_inside) inside the pressure measuring device that changes according to the environment and time.

5 is a diagram illustrating a configuration of a differential pressure measuring device according to the present invention.

The differential pressure measuring apparatus of the present invention can be used for measuring the pressure of all fluids, but for the convenience of description, the following describes a case of measuring the water pressure using the differential pressure measuring apparatus of the present invention.

First, the differential pressure measuring apparatus of the present invention includes an upper housing 530 and a lower housing 550 coupled to each other, and two semiconductor gauge pressure sensors are installed in the upper housing 530.

Among the two semiconductor pressure sensors, the first sensor 510 shown on the left side of the drawing is for measuring water pressure, and the second sensor 520 shown on the right side of the drawing is a sensor for correcting an error, The sensor 510 and the second sensor 520 use the same sensor model, that is, the same full scale manufactured at the same time. Although the same model may not be completely identical in characteristics of the first sensor 510 and the second sensor 520, two pressure sensors having the most similar characteristics are selected and used.

As illustrated in FIG. 1, the first sensor 510 and the second sensor 520 are provided with diaphragms 512 and 522 at the center of the sensor frames 511 and 521, and are installed in the first and second accommodating parts. O-rings 513 and 523 are provided around the sensor frames 511 and 521 to block the flow of fluid.

An upper surface and a lower surface are opened in the upper housing 530, and a first accommodating part accommodating the first sensor 510 is formed therein. The upper surface of the first accommodating part is opened by the through hole 534, and the pressure is increased. When the measuring device is disposed in the water, the water pressure is applied to the diaphragm 512 of the first sensor 510 through the through hole 534.

In addition, the connecting portion 540 used to set the initial value of the second sensor 520 to be described later is connected to the first receiving portion through the through hole 534, the connecting portion 540 on the inner surface of the through hole 534 Thread may be formed to be coupled to the thread formed on the outer surface of the).

On the other hand, the second receiving portion for receiving the second sensor 520 is formed on the right side of the first receiving portion. The lower surface of the second accommodating part is open but the upper surface is closed, and a liquid is filled between the upper surface of the second accommodating part and the upper surface of the diaphragm 522 of the second sensor 520.

In addition, the adjusting unit 560 for controlling the pressure applied to the diaphragm 522 of the second sensor 520 by adjusting the distance between the upper surface of the second accommodating portion and the second sensor 520 includes a second accommodating portion. It is installed on the lower surface. The adjuster 560 adjusts the pressure applied by the liquid to the diaphragm 512 522 by pushing the sensor frame 521 of the second sensor 520 upward, and according to a preferred embodiment of the present invention 560 is a screw thread formed on the outer surface thereof is coupled with a screw thread formed on the inner surface of the second receiving portion to adjust the distance between the second sensor 520 and the upper surface of the second receiving portion to adjust the pressure of the liquid applied to the diaphragm 522. do.

In addition, a bolt hole 532 is formed at a side of the upper housing 530 so as to be coupled to the lower housing 550 by a bolt.

On the other hand, the lower housing 550 has an upper surface open so that air received therein is provided on the lower surfaces of the diaphragms 512 and 522 of the first sensor 510 and the second sensor 520 through the lower surface of the first accommodating part and the lower surface of the second accommodating part. It is configured to apply the same air pressure. An upper surface of the lower housing 550 is provided with an o-ring 554 to block liquid from flowing in from the outside when the upper housing 530 is coupled, and may be coupled to the upper housing 530 by a bolt. The bolt hole 552 is formed to be.

Hereinafter, the method of measuring pressure using the pressure measuring apparatus of this invention is demonstrated.

After combining the upper housing 530 and the lower housing 550 in a state where a predetermined pressure is applied by the liquid filled between the upper surface of the second accommodating portion and the diaphragm 522 of the second sensor 520, the water pressure is measured. In order to measure the water pressure. In this case, the pressure measured by the first sensor 510 is as shown in Equation 3 below, and the pressure measured by the second sensor 520 for error correction is as shown in Equation 4 below.

P1 = P_air + P_water-P_inside

P2 = P_liquid-P_inside

At this time, since the internal air pressure applied to the first sensor 510 and the second sensor 520 is the same as P_inside, P_inside is eliminated from Equation 3 and Equation 4 and solved for P_water, which is the water pressure to be measured. The following equation (5) is obtained.

P_water = P1-P2-P_air + P_liquid

Accordingly, the measured value P1 of the first sensor 510, the measured value P2 of the second sensor 520, the atmospheric pressure P_air, and the pressure P_liquid set to be initially applied to the second sensor 520. Knowing this, it is possible to accurately measure the water pressure at the position where the pressure measuring device is installed.

Here, the measured value P1 of the first sensor 510 and the measured value P2 of the second sensor 520 can be known from the sensor, and the atmospheric pressure P_air can also be easily known from the data of the Meteorological Agency. Since the pressure P_liquid set to be initially applied to the second sensor 520 is equal to a constant, the water pressure can be measured.

When the water pressure is measured according to Equation 5, even if the air pressure P_inside inside the measuring device is changed due to a change in the external environment or a sensor error occurs due to aging of the sensor itself, the error is measured by the first sensor 510. ) And the second sensor 520 are commonly canceled by each other by the " P1-P2 "

In addition, the present invention applies P_liquid at a pressure similar to that of the actual measuring point in advance, so that the period drift that occurs during long-term use under pressure also works similarly to the two sensors, and this also cancels each other out.

Hereinafter, a method of setting the initial pressure of the second sensor 520 which acts as a constant in the above-described equation (5) will be described.

First, in a state where the upper housing 530 and the lower housing 550 are not coupled in the atmosphere, the liquid is filled in the upper surface of the second accommodating part and the second sensor 520 is accommodated in the second accommodating part, and then the adjusting part The pressure _liquid by the liquid is applied to the second sensor 520 by adjusting the distance between the second sensor 520 and the upper end of the second accommodating part using the 560.

Thereafter, the connecting portion 540 is coupled to the through hole 534 formed in the first accommodating portion, and the pressure measurement liquid (eg, “water”) is first introduced through the transparent tube inserted into the connecting portion 540. The space between the receiving portion and the diaphragm 512 522 of the first sensor 510 is filled.

Then, the first sensor 510 outputs a sensor value corresponding to the difference between the pressure P_water and the air pressure P_inside by the pressure P_water and the atmospheric pressure P_air caused by the water introduced through the connection part 540. In this case, since the atmospheric pressure and the air pressure are the same value, the output value of the first sensor 510 becomes P_water.

On the other hand, the second sensor 520 outputs a sensor value corresponding to the difference between the pressure P_liquid and the air pressure P_inside by the liquid contained therein. Since this process is performed in the atmosphere, P_inside has the same value as P_air, which is atmospheric pressure.

Thereafter, the adjusting unit 560 is adjusted so that the measured value of the second sensor 520 is equal to the measured value of the first sensor 510, and the output values of the first sensor 510 and the second sensor 520 are adjusted. If this is the same, the height (H_water) of the water column on the tube installed at the connecting portion 540 at that time is measured.

At this time, the height H_water of the water column is equal to P_water, which represents the same pressure as P_liquid-P_inside, and the pressure P_liquid used to set the initial value of the second sensor 520 is equal to the initial value of the second sensor 520. It remains constant until it is reset.

At this time, the output value P1 of the first sensor 510 and the output value P2 of the second sensor 520 are each as shown in Equation 6 below.

P1 = P_water = H_water

P2 = P_liquid-P_air

Since P1 and P2 in Equation 6 are the same value, the following Equation 7 holds.

P_liquid = P_water + P_air = H_water + P_air

In the above Equation 7, H_water can obtain the value by measuring the height of the water column of the tube installed in the connecting portion 540, P_air can obtain the correct value through the data of the Meteorological Administration, the error of the first sensor 510 The pressure P_liquid set in the second sensor 520 for correction can be easily obtained.

On the other hand, if the initial value (P_liquid) of the second sensor 520 to compensate for the error is set, and combines the upper housing 530 and the lower housing 550, P_inside is changed as the internal air pressure increases. However, in this case, since P_inside acts on the first sensor 510 and the second sensor 520 in the same manner, the P_inside cancels each other and does not affect the measurement result.

As a result, the pressure measuring apparatus of the present invention subtracts the measured value of the second sensor 520 from the measured value of the first sensor 510, as described in Equation 5, and sets the initial pressure of the second sensor 520. The water pressure can be measured accurately by adding the P_liquid value and subtracting the atmospheric pressure P_air at the time of measurement.

In this case, the present invention uses the same first sensor 510 for the pressure measurement and the second sensor 520 for error compensation, so that even if the air pressure inside the measuring device is changed due to external environmental changes, This affects the measured values of both sensors, and these two sensors cancel each other out, so these effects cancel each other out.

In addition, the present invention applies P_liquid at a pressure similar to that of the actual measuring point in advance, so that the period drift that occurs during long-term use under pressure also works similarly to the two sensors, and this also cancels each other out.

So far, the configuration and operation of the pressure measuring device of the present invention have been described taking the method of measuring water pressure as an example. However, it should be noted that the pressure measuring device of the present invention can be used to measure the pressure of all liquids.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a diagram schematically showing a configuration of a general gauge pressure sensor.

2 is a diagram illustrating an example of measuring water pressure with a semiconductor gauge pressure sensor.

3 is a diagram illustrating another example of measuring the water pressure with the semiconductor gauge pressure sensor.

It is a figure which shows the example of the pressure measuring apparatus which measures water pressure with a semiconductor absolute pressure sensor.

5 is a diagram illustrating a configuration of a differential pressure measuring device according to the present invention.

Claims (7)

A first sensor unit and a second sensor unit measuring a difference between an upper pressure and a lower pressure applied to the diaphragm; An upper housing having an upper surface and a lower surface open and having a first accommodating portion accommodating the first sensor portion therein, and a second accommodating portion with a lower surface open and accommodating the second sensor portion therein; A lower housing coupled to the upper housing such that an upper surface thereof is opened so that air received therein applies air pressure to the lower portion of the diaphragm of the first sensor portion and the second sensor portion through the lower surface of the first accommodating portion and the second accommodating portion. ; A connection part coupled to a through hole formed in an upper surface of the first accommodating part, for introducing a pressure measurement liquid between an upper surface of the diaphragm of the first accommodating part and an upper surface of the first sensor part through a tube inserted therein; And An initial pressure value applied to the diaphragm of the second sensor part by applying a liquid filled between the upper surface of the second accommodating part and the upper surface of the diaphragm of the second sensor part by adjusting a distance between the upper surface of the second accommodating part and the second sensor part; Underwater pressure measuring device comprising a control unit for adjusting the. delete delete According to claim 1, wherein the pressure measuring device The measured value of the first sensor unit is corrected to the measured value of the second sensor unit and the initial pressure value, and the pressure of the measurement target liquid applied from the outside of the pressure measuring device is measured through the through hole. Submersible pressure measuring device. The apparatus of claim 4, wherein the pressure measuring device And subtracting the second sensor value from the measured value of the first sensor unit, and adding the initial pressure value to measure the pressure of the liquid applied from the outside of the pressure measuring device. 6. The method of claim 1, 4 or 5, wherein the initial pressure value is Underwater pressure, characterized in that obtained by measuring the height of the liquid filled in the tube when the measurement value of the first sensor unit and the measurement value of the second sensor unit is the same when the liquid to be measured is applied through the tube. Measuring device. delete

Images