CN204516182U - A kind of row's formula pressure tester with touring electrical measurement digital display - Google Patents

Abstract

The utility model provides a row-type pressure measuring device with a roving electric measuring digital display, comprising: more than two groups of pressure measuring components, each group of pressure measuring components includes: a pressure measuring cylinder, a pressure measuring cylinder arranged on the top The communication positioning tube, the pressure measuring tube connected with the communication positioning tube, the conduit communicating with the compressed air in the pressure measuring cylinder, and the valve arranged on the conduit; the differential pressure sensor, and more than two groups of pressure measuring components pass through The respective valves are connected with the differential pressure sensors; the straightedge used to calibrate the liquid level in the pressure measuring tubes of each pressure measuring assembly. The utility model has a row-type piezometric device with roving electric measurement and digital display, which can widely replace the traditional row-type piezometric tubes for measuring water head pressure in basic experiments of fluid mechanics and hydraulics. It cleverly applies the basic principles of fluid mechanics and is very good It unifies traditional measurement means and modern measurement technology, and has excellent teaching effect.

Description

A row-type pressure measuring device with roving electric measuring digital display

technical field

The utility model relates to the field of experimental measurement, in particular to a row-type pressure measuring device with a circuit electric measuring digital display.

Background technique

Hydraulics and Fluid Mechanics is a major professional basic course for many majors in engineering colleges. Modern hydraulics is based on the three pillars of experiment, theory and calculation. Therefore, experiment is an indispensable content in the teaching process. Among them, the piezometric tube is one of the most commonly used pressure measuring instruments in the process of hydraulic and fluid mechanics experiments. It is the simplest type of liquid column pressure gauge. It uses a transparent straight glass tube with a diameter of The lower end of the pipe is sealed with the measuring point through a hose, and the upper end of the pipe is open to the atmosphere. According to the rising height of the liquid column in the pressure pipe, the pressure at that point can be obtained. In the teaching experiment, the liquid is usually water, that is, the piezometric head, which is the total potential energy per unit weight of water represented by the height from the piezometric tube water surface to the reference plane. The piezometric tube is usually installed on the pressure measuring frame, and the head height of the piezometric tube will be used to mark the scale line on the piezometric tube, lay coordinate paper on the pressure measuring frame or fix the scale on the pressure measuring frame, and measure it manually by human eyes water column height. In an actual experiment, it is often necessary to measure the pressure signals of multiple parts of the experimental pipe or water tank at the same time. Therefore, according to the needs of the experiment, multiple piezometric tubes are installed side by side on the pressure measuring frame at the same level to form a group of rows. Type piezometric tube, and the height of this kind of experimental teaching piezometric tube is generally within 100cm, mainly to measure low-pressure water head.

With the development of modern measurement technology, many experimental teaching instruments of fluid mechanics have been introduced and applied. For example, for multiple pressure measurement points that need to use row-type pressure measurement tubes, such experimental teaching instruments at home and abroad are directly replaced by multiple pressure sensors, and cooperate with pressure transmitters, multi-input digital display heads or Digital display single meter with microcomputer multi-channel A/D input circuit switching. However, as a student teaching experimental instrument, we always believe that the use of traditional and most commonly used pressure measuring instruments such as piezometric tubes is an indispensable basic knowledge that students should learn and master in experimental teaching, but at the same time they should also learn Modern measurement technology, and more accurate modern measurement instruments can be used to calibrate the error of human eye and hand measurement, so as to improve the traditional basic experimental hands-on ability in comparison.

Therefore, the row-type piezometric tube equipped with modern measurement technology should be like this. It can not only measure the water head height manually with the traditional piezometric tube human eyes for multiple pressure measuring points in the experiment, but also can synchronously cooperate with the connected pressure sensor. The head of the pressure transmitter digitally displays the water head value of each piezometric tube in real time. This kind of row-type piezometric tube with synchronous digital display is not available on the market, and there is no design plan. Several problems involved in it may be difficult to solve well:

(1) The row-type piezometric tubes are fixed side by side by the shelf and stand vertically on the test bench. The same is true for the scale scale of the row-type piezometric tubes. A fixed height scale is used to uniformly measure the height of the water column of each side-by-side piezometric tube. However, the zero point of the scale is suspended at a certain height close to the test bench. With the height of the installation position, there is an up and down deviation relative to the test bench. It is difficult to maintain the zero point of the differential pressure measured by the differential sensor accurately.

(2) Multiple sensors will generate multiple zero points, which is not only costly and troublesome in experimental adjustment, but also easily accumulates and superimposes the different measurement errors of multiple sensors when they are compared with each other and substituted into a formula for calculation.

(3) If the pressure measuring end of the sensor is directly connected to the pressure measuring point of the water body through the waterway, because the pressure of the sensor is transmitted through the water body, the interface of the sensor end is sealed, and there is a sealed cavity inside, so it is difficult to completely empty the air. If tiny air bubbles remain, the pressurized water column in the connecting pipe cannot directly act on the pressure chip of the sensor, and because the pressure transmission channel in the sensor is very small, a large surface tension will be generated on the liquid-gas interface, and its value can be It can reach 1-5 cm water column, or even larger, and the pressure measurement error can reach more than 10% for the low-pressure water head of the experimental piezometer within 100 cm.

Utility model content

The utility model provides a row-type pressure-measuring device with a roving electric measuring digital display, which can widely replace the traditional row-type pressure-measuring tubes used in the basic experiments of fluid mechanics and hydraulics to measure the pressure of the water head, and cleverly applies the basic principles of fluid mechanics , a good unification of traditional measurement methods and modern measurement techniques, with excellent teaching effect.

A row-type pressure measuring device with a roving electric measuring digital display, comprising:

More than two groups of pressure measuring components, each group of pressure measuring components includes: a pressure measuring cylinder, a connecting positioning tube arranged on the top of the pressure measuring cylinder, a pressure measuring tube connected to the communicating positioning tube, and a pressure measuring tube connected to the pressure measuring tube A conduit communicating with the compressed air in the barrel and a valve arranged on the conduit;

A differential pressure sensor, more than two groups of pressure measuring components are connected to the differential pressure sensor through respective valves;

Straight edge used to calibrate the liquid level in the piezometer tube of each piezometer assembly.

In the utility model, more than two groups (including two groups) of pressure measurement components, each group of pressure measurement components include: a pressure measurement cylinder, a communication positioning tube arranged on the top of the pressure measurement cylinder, connected to the communication positioning tube The pressure measuring tube, the conduit communicating with the compressed air in the pressure measuring cylinder, and the valve arranged on the conduit. Therefore, each set of pressure measuring components includes: a pressure measuring cylinder, a connecting positioning tube, a pressure measuring tube, a conduit and a valve, and a valve is connected through a conduit, and the valve in each set of pressure measuring components is connected to the pressure The differential sensor is connected, and the differential pressure sensor can be used to detect the pressure difference between the compressed air in the pressure measuring cylinder and the outside air in different pressure measuring components by opening or closing the valve. Therefore, it can reduce the superposition error of multiple sensors, the trouble of adjusting multiple zero points, and it will be more accurate to use the same differential pressure sensor for circuit switching measurement of the row-type piezometric tubes.

In order to reduce the superposition error of multiple sensors and the troublesome adjustment of multiple zero points, it is more accurate to use the same differential pressure sensor for circuit switching measurement of row-type piezometric tubes (that is, different pressure-measuring components). For this reason, a gas circuit on-off control switching channel that selects one of the multiple gas circuit on-off is specially designed. The n pressure measuring tubes pass through the ventilation and pressure measuring hoses of n pressure measuring cylinders, and are respectively sealed and connected to one vent port of n 2-way electronically controlled micro-air valves (a type of valve), and the other end of n 2-way vent valves The vent port is then sealed and connected to the (n+1) channel trachea joint through a hose, and finally the n+1 channel of the trachea joint is sealed and connected to one measurement port of the differential pressure sensor with a vent tube, and the other differential pressure sensor measures The interface is directly connected to the atmosphere, and the differential pressure signal is finally sent to the smart meter head of the pressure transmitter of the electrical measuring instrument. This type of DC electronically controlled micro-air valve is normally closed, and the air path will be opened when the power is turned on. Therefore, the DC circuit of n electronically controlled micro-air valves can be controlled by switching the circuit switching of the band selection switch of the electric measuring instrument. The air path of n air valves is switched on and off to realize the function of measuring the water head of n piezometer tubes (ie, the reading value of the water column scale of the piezometer tube and the pressure value of the measuring point relative to the atmospheric pressure) with a differential pressure sensor.

Of course, the structure of the above-mentioned pressure measuring cylinder will be compressed with the sealing air column, and the actual water level inside the pressure measuring cylinder will be slightly higher than the reference zero elevation of the bottom surface of the Unicom positioning tube. Assuming the difference is Δh, we can calculate and analyze it here How much its error affects this measuring device. For desktop hydrodynamic hydraulic experiments, the piezometric head height is all low-pressure head below 1m. If the piezometric head reaches 1m, the maximum absolute error will occur. Assume that the volume of the sealed air column before compression is V ₁ , and the compression The back volume is V ₂ and is calculated as follows:

According to the gas equation, PV/T=nR, gas P pressure (air is atmospheric pressure), V is air volume, T is the Kelvin temperature of air (273.15+ degrees Celsius), n is the amount of air substance (number of moles), R is the gas constant.

For the sealed air column in the pressure measuring cylinder, T, n, R are all fixed values;

It is known that P ₁ = 1 atmosphere pressure = 1000 cm water column before initial compression, and the height of the sealed air column h = 1 cm;

P ₂ after compression = 1000cm water column + 100cm water column = 1100cm water column;

P ₁ ×V ₁ =P ₂ ×V ₂ ;

P ₁ ×h=P ₂ ×(h-Δh);

Calculate the absolute error: Δh=hP ₁ ×h/P ₂ ＝0.091cm;

Relative error = Δh/height of piezometer water column = 0.091/100 = 0.091%;

When the water column of the piezometric tube is 1cm, P ₂ =1001cm water column,

Absolute error: Δh = 0.000999cm, relative error: 0.0999%

It can be seen from the above calculation that the error caused by this kind of air compression is far smaller than the system design error level 1 accuracy. In the range of 0-100cm water column low pressure measurement, the maximum absolute error is also less than 0.91mm, which can be completely ignored. According to the above calculation, it can also be obtained that when designing the pressure measuring cylinder, the smaller the distance between the bottom surface of the Unicom positioning tube inserted at the top and the top surface of the pressure measuring cylinder, the smaller the error, and the error of leaving a distance of 1 cm is less than one thousandth, which is sufficient.

If the compressed air error in the connected ventilated piezometer is considered, the calculation is as follows: the length of the ventilated piezometer is generally <100cm, and the inner diameter is about 2mm. Considering the maximum error when the length is 100cm and the maximum water head of the piezometer is 100cm water column, set the ventilated piezometer The volume reduced by compression in the tube is ΔV, then according to the previous gas equation,

ΔV=V ₁ -V ₂ =V ₁ -(P ₁ /P ₂ ×V ₁ );

=3.14× ^0.12 ×100-1000/1100×3.14× ^0.12 ×100;

= 0.29cm ³ ;

For a cylindrical pressure measuring cylinder with a diameter of 4 cm, the aforementioned Δh error will increase by 0.02 cm, and the overall error is only 0.111%.

To sum up, in the structure of the pressure measuring cylinder designed above, the measurement error of the water head pressure value of the piezometric tube brought about by the change of the volume of air compression is at most only one thousandth level, which is completely acceptable compared with the nominal accuracy of the first-grade precision of this teaching experiment instrument. neglect.

Preferably, the bottom surface of the connecting positioning pipe in each pressure measuring assembly is on the same level as the zero scale of the ruler. By making the bottom surface of the Unicom positioning tube and the zero point of the piezometer scale be at the same level, the zero point of the pressure difference measured by the pressure difference sensor relative to the atmospheric pressure and the elevation zero point of the piezometric tube scale hanging in the air (the reference zero elevation of the piezometric tube water head) can be automatically determined, etc. zero.

Preferably, in each set of pressure measuring components, the top of the pressure measuring tube is provided with an opening for venting to the atmosphere, and the bottom of the pressure measuring tube is in communication with the communication positioning tube through a hose.

Preferably, in each set of pressure measuring components, the bottom of the pressure measuring cylinder is provided with a water inlet.

Preferably, the row-type pressure measuring device with roving electric measurement and digital display further includes: a fixed bracket on which the ruler and the pressure-measuring tubes in each pressure-measuring component are installed.

Further preferably, the fixed bracket is provided with a horizontal measuring chute, and the horizontal measuring chute is provided with a slide block, and the ruler is mounted on the slide block. By sliding the slider in the horizontal measuring chute, the straightedge can be adjusted to different positions, so as to realize the calibration of the liquid level in the pressure measuring tube of each pressure measuring component.

More preferably, the ruler is provided with an elongated hole, and the ruler is fixed on the sliding block by cooperating with the elongated hole through a screw, and when the screw is in a loosened state, it can slide in the elongated hole , thereby adjusting the position of the straightedge on the fixed support, thereby facilitating the adjustment of the zero scale of the straightedge and the bottom surface of the connected positioning tube at the same level.

Preferably, one measurement port of the differential pressure sensor is open to the atmosphere, and the other measurement port of the differential pressure sensor is connected to the valves in each pressure measurement assembly.

Preferably, in each set of pressure measuring components, one end of the conduit inserted into the pressure measuring cylinder is located between the bottom surface of the communication positioning tube and the top surface of the pressure measuring cylinder, and is higher than the connection positioning tube the underside.

Preferably, the row-type pressure measuring device with roving electric measuring digital display further includes: a pressure transmitter digital display head connected to the differential pressure sensor.

Preferably, the row-type pressure measuring device with roving electric measuring and digital display further includes: a selection switch connected to the valves in each pressure measuring assembly. By selecting the switch to close and open the valves in each pressure measuring assembly, the same differential pressure sensor can detect the pressure difference between the compressed air in the pressure measuring cylinder and the outside air in different pressure measuring assemblies.

From the above, compared with the traditional row-type piezometer, the utility model has the following advantages:

The liquid-gas conversion pressure measuring cylinder (referred to as the pressure measuring cylinder) with the structure of the Unicom positioning tube is ingeniously combined with the modern measuring instruments such as the gas circuit on-off switching system and the differential pressure sensor, which are traditional The head pressure measurement of the row-type piezometer tube is equipped with a high-precision synchronous itinerant measurement digital display system. It can be integrated into various fluid mechanics and hydraulics experimental teaching instruments, which not only allows students to compare and learn traditional pressure measurement methods and modern measurement techniques, but also allows students to further study the theoretical knowledge of fluid mechanics and the application of modern measurement techniques in experimental devices. The innovative application is a measurement device that can really help students' experimental teaching.

For multiple pressure measuring tubes in a row, after using the liquid-gas conversion pressure measuring cylinder, the electronically controlled micro-air valve is cleverly used to design a gas circuit on-off switching system with multiple gas paths. The gas path of the pressure measuring cylinder to be tested can realize the roving measurement of the water head of each tube of the row type piezometric tube with a differential pressure sensor, which effectively avoids the superposition error easily caused by multiple sensors, and facilitates the zero point adjustment of the sensor itself, Calibration greatly reduces the cost of the instrument while improving the accuracy of the experiment.

Through the liquid-gas stable pressure conversion technology of the pressure measuring cylinder, for the measurement of the low-pressure water head within 1m on the test bench, it avoids the liquid surface caused by the existence of small air bubbles that are difficult to empty when the liquid directly contacts the pressure sensor airtight connection pipe. Almost 10% pressure error caused by tension. The liquid pressure detection accuracy of the conventional fluid pressure sensor under the water head of 1m under the pressure of the low water head is greatly improved. At the same time, it also avoids the corrosion of the sensor caused by the long-term contact between the liquid and the sensor, and improves the service life of the sensor and the accuracy of long-term use.

Innovatively applying the principle of fluid mechanics, the Unicom positioning tube in the pressure measuring cylinder is designed, which can not only transmit the pressure of the pressure measuring point to the traditional pressure measuring tube through the sealed water circuit, forming a water column of the pressure measuring tube, but also transmit the pressure to the pressure measuring tube through the sealed air circuit. Differential pressure sensor, convenient and direct electrical measurement to obtain relative atmospheric pressure relative to zero elevation. Moreover, by making the bottom surface of the connecting positioning tube on the top of the piezometric tube be at the same level as the zero point of the piezometric tube scale, the zero point of the pressure difference relative to the atmospheric pressure measured by the differential pressure sensor and the zero point of the elevation where the piezometric tube scale is suspended can be automatically determined (the water head of the piezometric tube The reference zero elevation) guarantees the equal zero position, which solves the problem that it is difficult to unify the reference zero point when the traditional pressure measuring tube is equipped with a digital display pressure gauge.

In order to ensure that the bottom surface of the Unicom positioning tube on the top of the pressure measuring cylinder is on the same level as the zero point of the pressure measuring tube scale, and to facilitate the adjustment of the hanging height deviation of the pressure measuring tube scale that is easy to cause during the processing of the pressure measuring frame, a special design can be made to fine-tune the distance up and down in the vertical direction. The scale of the pressure measuring frame can be easily eliminated by adjusting the actual measurement.

Description of drawings

Fig. 1 is a structural schematic diagram of a row-type pressure measuring device with a roving electric measuring digital display of the present invention.

Detailed ways

As shown in Figure 1, it is a row-type pressure measuring device with a roving electric measuring digital display of the present invention, including: more than two groups of pressure measuring components, each group of pressure measuring components includes: pressure measuring cylinder 11, located in the pressure measuring The communication positioning tube 10 at the top of the cylinder 11, the pressure measuring tube 2 connected with the communication positioning tube 10, the conduit (ventilation tube 13 and ventilation pressure measurement hose 15) communicated with the compressed air in the pressure measurement cylinder 11, and the conduit (ventilation pressure measurement hose 15) arranged on the conduit (passage The valve 16 on the trachea 13 and the ventilation pressure measuring hose 15); the differential pressure sensor 19, and more than two groups of pressure measuring components are connected with the differential pressure sensor 19 through their respective valves 16; used to calibrate the pressure measuring tube 2 in each pressure measuring component Ruler 3 of the inner liquid level.

The bottom surface of the communication positioning pipe 10 in each pressure measuring assembly is on the same level as the zero scale of the ruler 3 . By making the bottom surface of the Unicom positioning tube 10 and the zero point of the piezometric tube scale (i.e. ruler 3) on the same level, the zero point of the pressure difference measured by the differential pressure sensor 19 relative to the atmospheric pressure and the zero point of the elevation where the piezometric tube scale is suspended can be automatically determined (the piezometric tube head reference zero elevation) to maintain equal zero. In each group of pressure measuring components, the top of the pressure measuring tube 2 is provided with an opening for venting to the atmosphere, and the bottom of the pressure measuring tube 2 communicates with a communication positioning tube 10 through a flexible hose 9 . In each group of pressure measuring components, a water inlet 4 is provided at the bottom of the pressure measuring cylinder 11 .

The row-type pressure measuring device with circuit electric measurement and digital display also includes: a fixed bracket 1, a ruler 3 and pressure measuring tubes 2 in each pressure measuring component are installed on the fixed bracket 1.

The fixed support 1 is provided with a horizontal measuring chute 8, and the horizontal measuring chute 8 is provided with a slide block 5 on which the ruler 3 is installed. By sliding the slider 5 in the horizontal measuring chute 8, the straightedge can be adjusted to different positions, so as to realize the calibration of the liquid level in the pressure measuring tube 2 in each pressure measuring assembly.

The ruler 3 is provided with an elongated hole 6, and the ruler 3 is fixed on the slide block 5 by cooperating with the elongated hole 6 through a screw 7. When the screw 7 is in a loosened state, it can slide in the elongated hole 6, Thereby adjusting the position of the straightedge 3 on the fixed bracket 1, thereby conveniently adjusting the zero scale of the straightedge 3 to be on the same level as the bottom surface of the communicating positioning tube 10.

One measuring port 21 of the differential pressure sensor 19 is open to the atmosphere, and the other measuring port 20 of the differential pressure sensor 19 is connected to the valves 16 in each pressure measuring assembly.

In each group of pressure measuring components, one end of the conduit (ventilation tube 13 and ventilation pressure measuring hose 15) inserted into the pressure measuring cylinder 11 is located between the bottom surface of the communication positioning tube 10 and the top surface of the pressure measurement cylinder 11, and is higher than the communication positioning tube 10. the bottom surface of the tube 10.

The row-type pressure measuring device with roving electrical measurement and digital display also includes: a pressure transmitter digital display head 23 connected to the differential pressure sensor 19 .

The row type pressure measuring device with roving electric measuring digital display also includes: a selection switch 24 connected with the valve 16 in each pressure measuring assembly. By selecting the switch 24 to close and open the valves 16 in each pressure measuring assembly, the same differential pressure sensor 19 can detect the pressure difference between the compressed air in the pressure measuring cylinder 11 and the outside air in different pressure measuring assemblies.

In the accompanying drawing 1 of the row-type pressure-measuring device with roving electric measuring digital display of the utility model, two groups of pressure-measuring components are taken as an example. The row-type pressure measuring device with circuit electric measurement and digital display has more than two pressure measuring tubes 2 installed side by side on the fixed bracket 1 vertically. Under the support of fixed support 1, it can be vertically placed on the desktop 25 adjusted to level, and a horizontal measurement chute 8 is arranged on the fixed support 1 top, and a slide block 5 is suspended on the horizontal measurement chute 8, and a ruler 3 ( There is a vertical elongated hole 6 on the top of the transparent) and is fixed on the slider 5 by screws 7. When the slider 5 is moved horizontally, the transparent ruler 3 can be used to measure each pressure measuring tube with the same zero-elevation reference plane 2 in the height of the water column. Simultaneously in order to keep the zero elevation horizontal plane 26 of the ruler on the same level as the bottom surface of the Unicom positioning tube 10 inserted into the top of the pressure measuring cylinder 11, the vertical elongated hole 6 that can be used to connect the fixed ruler 3 through the bottom of the slider 5 can be fine-tuned The up and down fixed position of ruler 3.

The fixed bracket 1 is placed on a horizontally adjusted experimental desktop 25, and a row of liquid-gas conversion pressure measuring cylinders 11 (ie The pressure measuring cylinder 11) can be made of transparent plexiglass material, and the internal water storage is clearly visible, which is convenient for experimental observation. Moreover, each pressure measuring cylinder 11 has the same internal and external structure and size, and is fixedly bonded to the same horizontal connection base plate 14 . The height of the pressure measuring cylinder 11 is about 1 cm higher than the horizontal plane at the zero point of the ruler 3 . The pressure measuring cylinder 11 can be a hollow cylinder or a polygonal hollow cylinder structure. As a row type pressure measuring cylinder, each cylinder wall can be directly vertically sealed and bonded to the same connecting bottom plate 14, so that the connecting bottom plate 14 can be used as a seal for each pressure measuring cylinder 11. bottom plate. There is a small hole on the top surface of each pressure measuring cylinder 11, and a connecting positioning tube 10 with the same outer diameter as the water inlet pipe of the water inlet 4 at the bottom of the pressure measuring tube 2 is vertically inserted and sealed. The water inlet pipe of Unicom positioning pipe 10 and water inlet 4 has a larger inner diameter of about 4mm. The Unicom positioning pipe 10 is about 1 cm higher than the top surface, which is convenient for sealing the external PVC water hose 9, and is sealed and communicated with the water inlet 4 at the bottom of the corresponding piezometric tube 2, forming a sealed water duct for the piezometric tube 2 water column. The Unicom positioning tube 10 is inserted into the pressure measuring cylinder 11 to a depth of about 1 cm, and the bottom surface is horizontal, and kept on the same plane as the horizontal plane 26 at the zero point of the ruler 3 . The lower part of the side wall of the pressure measuring cylinder 11 has a pressure measuring water inlet 12 close to the bottom surface, which can be sealed and connected to the external water hose to be connected to pressure measuring points such as experimental pipelines and water tanks to be measured. The pressure measuring points are all connected to water. After connecting the pressure measuring cylinder 11, water will enter the inside of the pressure measuring cylinder 11 from the water inlet 12 of the bottom side wall. When the water level reaches the horizontal surface 26 of the bottom surface of the top Unicom positioning tube 10, the water level will no longer rise. The water will enter the Unicom positioning tube 10, and then enter the piezometer tube 2 to form a piezometric tube water column 27. After the water column height of each piezometer tube is stable, slide the ruler 3 horizontally, and measure the water column height values of each tube respectively, which is the value corresponding to each test tube. The head pressure at the pressure point relative to the zero reference level 26. A section of air column will be sealed from the bottom horizontal surface 26 of the Unicom positioning tube 10 of the pressure measuring cylinder 11 to its top, because the horizontal plane 26 of the bottom surface of the Unicom positioning tube 10 is in the same plane as the horizontal plane 26 of the zero point of the scale, so the pressure of the compressed air column in this section is It is the sum of the head pressure in the piezometer tube and the atmospheric pressure.

In order to measure the pressure of this section of sealed compressed air column, a small hole is opened on the upper part of the pressure measuring cylinder 11, and a stainless steel vent pipe 13 with an inner diameter of 2mm is inserted into it by sealing and bonding (it can be inserted from the top or from the upper side wall), The bottom surface of the vent pipe 13 should not touch the highest water surface in the bucket, and the vent pipe 13 can be sealed and externally connected to the hollow ventilating pressure measuring hose 15 about 1 cm outside the pressure measuring cylinder 11.

In order to reduce the superposition error of multiple sensors and the troublesome adjustment of multiple zero points, it will be more accurate to use the same differential pressure sensor for the row-type piezometric tube to switch and measure. The two pressure measuring tubes 2 pass through the ventilation and pressure measuring hoses 15 of the two pressure measuring cylinders 11, and are respectively sealed and connected to one of the air vents of the two valves 16 (specifically, two electronically controlled miniature air valves), and the two valves 16 ( Specifically, the vent port at the other end of the 2-way electronically controlled micro-air valve) is then sealed and connected to the 3-way air pipe joint 18 through a flexible hose 17, and finally the third passage of the air pipe joint 18 is sealed and connected to the differential pressure sensor 19 with a ventilation hose On one measurement interface 20 of the pressure difference sensor 19, the other measurement interface 21 is directly connected to the atmosphere, and the pressure difference signal is finally sent to the intelligent digital display head 23 of the pressure transmitter of the electric measuring instrument 22. This type of 2-way electronically controlled micro-air valve is normally closed, and the air path is opened when the power is turned on. Therefore, the DC circuit of the 2 electronically controlled micro-air valves is controlled by the 24-way switching of the band selection switch of the electrical measuring instrument. That is to say, the on-off of the gas path of the valve 16 can be controlled, and a differential pressure sensor 19 can be used to measure the water heads of two piezometric tubes (ie, the reading value of the water column scale of the piezometric tube, the pressure value of the measuring point relative to the atmospheric pressure). Among them, the 44.8cm displayed by the intelligent digital display head 23 of the pressure transmitter is the water column data during use.

During the specific experiment, the desktop 25 will be leveled first, and the water inlet 12 of each pressure measuring cylinder 11 will be connected with the thin tubes of each pressure measuring point such as the experimental pipeline to be tested and the water tank to be sealed and connected through the water hose. 1. When the water tank is not filled with water at the beginning of the experiment, the pipeline connecting the pressure measuring cylinder 11 and the measuring interface 21 of the differential pressure sensor 19 is directly connected to the atmosphere, and is equal to the pressure of the measuring interface 20. At this time, the pressure connected to the differential pressure sensor 19 needs to be adjusted The digital display head 23 of the transmitter is initially zeroed, and then the water pump of the experimental instrument is started to supply water, and the experiment is started. According to each experimental procedure, after the water column of the pressure measuring tube 2 is stabilized, the ruler 3 on the pressure measuring frame can be slid side by side to The height of the water column of the piezometric tube is measured by manual human eyes in the traditional way, and the liquid-gas pressure conduction path corresponding to each piezometric tube can be selectively opened through the band switch 24, and compared with the electric measuring digital display instrument 22 for high-precision measurement.

Finally, it should be noted that obviously, the above-mentioned embodiments are only examples for clearly illustrating the utility model, rather than limiting the implementation manner. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the protection scope of the present utility model.

Claims (10)

1. A row-type pressure measuring device with a roving electric measuring digital display, characterized in that it comprises: More than two groups of pressure measuring components, each group of pressure measuring components includes: a pressure measuring cylinder, a connecting positioning tube arranged on the top of the pressure measuring cylinder, a pressure measuring tube connected to the communicating positioning tube, and a pressure measuring tube connected to the pressure measuring tube A conduit communicating with the compressed air in the cylinder and a valve arranged on the conduit; A differential pressure sensor, more than two groups of pressure measuring components are connected to the differential pressure sensor through respective valves; Straight edge used to calibrate the liquid level in the piezometer tube of each piezometer assembly. 2. The row-type pressure measuring device with roving electric measuring digital display according to claim 1, characterized in that the bottom surface of the connecting positioning tube in each pressure measuring assembly is on the same level as the zero scale of the ruler. 3. The row-type pressure measuring device with roving electric measuring digital display according to claim 1, characterized in that, in each group of pressure measuring components, the top of the pressure measuring tube is provided with an opening for ventilating the atmosphere, so The bottom of the pressure measuring tube communicates with the communication positioning tube through a flexible tube. 4. The row-type pressure measuring device with roving electric measuring digital display according to claim 1, characterized in that, in each group of pressure measuring components, the bottom of the pressure measuring cylinder is provided with a water inlet. 5. The row-type pressure measuring device with roving electric measuring digital display according to claim 1, further comprising: a fixed bracket, and the pressure measuring tubes in the ruler and each pressure measuring assembly are installed on the on the fixed bracket. 6. The row-type pressure measuring device with roving electric measuring digital display according to claim 5, wherein said fixed support is provided with a horizontal measuring chute, and said horizontal measuring chute is provided with a slide block, said A ruler is mounted on the slider. 7. The row-type pressure measuring device with roving electric measuring digital display according to claim 6, characterized in that, the said ruler is provided with an elongated hole, and the ruler is fixed with the elongated hole by screws on the slider. 8. The row-type pressure measuring device with roving electrical measurement and digital display according to claim 1, characterized in that one of the measuring ports in the differential pressure sensor is open to the atmosphere, and the other of the differential pressure sensor is connected to the atmosphere. The measuring ports are connected to the valves in each pressure measuring assembly. 9. The row-type pressure measuring device with roving electric measuring digital display according to claim 1, characterized in that, in each group of pressure measuring components, the end of the catheter inserted into the pressure measuring cylinder is located at the communication position Between the bottom surface of the tube and the top surface of the pressure measuring cylinder, and higher than the bottom surface of the communication positioning tube. 10. The row-type pressure measuring device with roving electrical measuring and digital display according to claim 1, further comprising: a pressure transmitter digital display head connected to the differential pressure sensor.