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Detailed Explanation of ADM Features

Release date:2020-12-16     Author:     Visitors:1741

Detailed Explanation of ADM Features 

 

This article explains the features of ADM in detail to help better understand ADM deformation monitoring system.

1. Aerospace-grade, Three-Axis MEMS Sensor to ensure high precision.

MEMS Sensors are classified into civil, commercial, industrial, military and aerospace grades according to application levels. ADM uses aerospace grade high-precision three-axis sensor. This high-standard configuration ensures that ADM can work stably under various extreme environments and output high-precision data in real time.

 

2. Temperature compensation to ensure stable data

All the data output by any kinds of electronic sensors will be affected by temperature. Even the data output by same sensor at different temperatures may fluctuate greatly, which will also affect stability of the final data. ADM adopts a unique temperature compensation model, which can continuously output stable and reliable data between -40℃and +60℃, and the data fluctuation is only 0.01mm.

 

3. Three axis calibration, accurate direction

All inclinometers, including traditional inclinometers, digital inclinometers, in-place inclinometers and automatic array meter inclinometers, are equipped with triaxial MEMS sensors. The data output by Triaxial MEMS sensor is in x, y, z directions, that means the sensor itself has directionality.

 

The MEMS sensor is equipped in a stainless-steel probe. We designate a mark line on the surface of probes, and the direction of the mark line is X direction. How to ensure that the X direction of the MEMS sensor is completely consistent with the X direction on the surface of probes is another important factor affecting the accuracy and reliability of the data. If the X direction of the MEMS sensor cannot exactly consistent with the X direction on the probe, even use the aerospace-grade sensor, it cannot output reliable data.

 

The array displacement meter ADM is a flexible inclinometer, which is composed of several probes connected one by one. Each probe has a mark line on the surface to show X direction, we must ensure that the mark lines of all probes are in a straight line, so as to ensure the accuracy of the overall direction.

We use the fully automatic 3D direction calibration platform, the angular resolution is 1 ", and the absolute accuracy is 3". We calibrate the X direction of the MEMS sensor and the X direction on the surface of probe first. Then calibrate the direction of overall probes to ensure the accuracy of overall direction of ADM.

 

4. Torsion algorithm, deviation correction

After the ADM is installed, the ADM are tightly attached to the inner wall of the inclinometer casing. When the monitored structure has displacement change, it will apply external force to the inclinometer casing, which will cause the deformation of inclinometer casing. The ADM inside the inclinometer casing will also deform with the inclinometer casing and output the displacement value. The inclinometer casing is very likely to twist since the force of inclinometer casing in soil is uneven. And such torsion will greatly affect the data result.

 

As shown in Figure 1 below, assuming that the cylinder is an inclinometer casing with length L, the angle between the inclinometer casing and the gravity direction is α, and the direction of the black arrow is the monitoring direction A, then the horizontal displacement of the inclinometer casing in the direction A is d = L * sin α, and L is the length of the inclinometer casing.

As shown in Figure 2, the inclinometer casing has been twisted. The tube groove direction of the inclinometer casing has twisted at an angle of β. However, the angle α between the inclinometer casing and the gravity direction has not changed. Then the displacement in the horizontal direction d=L*sinα does not change, but changes the direction of horizontal displacement. After torsion, the direction of horizontal displacement is A+β. If the torsion hasn’t be corrected, the horizontal displacement in A direction is d2=L*sinα*cosβ. Then there will be displacement Δd= L*sinα *cosβ -L*sinα in direction A to be measured. But the actual situation is that the inclinometer casing is only twisted, and there is no displacement change in the horizontal direction. It can be seen from the above analysis that if the torsion of the inclinometer casing is not corrected, the actual measurement results will be seriously affected. The greater the torsion angle β, the greater the impact on the actual. Therefore, it is very necessary to correct the torsion of inclinometer casing.

 

The difference between initial offset angle and torsion correction.

First of all, it must be clear that the initial offset angle input in the cloud software has nothing to do with the torsion correction of the array displacement meter ADM.

 

The generation of initial offset angle: the initial offset angle is mainly composed of two factors.

(1)In the process of installing the inclinometer casing, due to insufficient installation technology or other reasons, the A direction of the inclinometer casing is different from the monitoring direction of the structure. The angle between the A direction of the inclinometer casing and the monitoring direction of the structure is called the initial offset angle.

 

(2)Due to the uneven force around the casing wall during the installation of the inclinometer casing, or because the old measuring borehole is subjected to the pressure in different directions for a long time in the rock and soil, the inclinometer casing will displace or rotate, and the casing groove of the inclinometer casing will also rotate. The without cable end of the ADM is equipped with a directional wheel, and the with cable end is equipped with a guide wheel. In the process of lowering the ADM, the directional wheel of the far cable end slides down along with the casing groove. The direction of the directional wheel is also changed due to the rotating casing groove. The change of the direction of the directional wheel leads to the change of the mark line direction of the ADM.

 

For example, the A direction of the casing groove at the top of the inclinometer casing is 90 degrees north by East, and the corresponding A direction of the casing groove at the bottom becomes 180 degrees north by east due to the force torsion of the casing groove. When we lower the ADM, directional wheel at the without-cable-side is lowered down along with the casing groove, the direction of ADM mark line is 90 degrees north by East. However, when the ADM is lowered to the bottom of the inclinometer casing, the directional wheel at the without-cable-side changes along with the casing groove. The directional wheel coincides with the casing groove at the bottom of the inclinometer casing, and the mark line also points to 180 degrees north by East. Since the ADM has not been pressed down at this time, the ADM is suspended in the inclinometer casing. Only the directional wheel at the bottom touches the inner casing wall of the inclinometer casing, and the ADM is not affected by other external forces except gravity. So the mark line of ADM will be in the same direction, that is, 180 degrees north by East. The direction of mark line observed at the top of inclinometer casing is also 180 degrees north by East. At this time, the angle between mark line and casing groove in direction A is the initial offset angle. In our example, the initial offset angle = 180 degrees north by East - 90 degrees north by East = 90 degrees.

 

5. Sectional installation design, convenient and fast to deploy

ADM’s sectional installation design is the world's first innovation, which truly realizes the reuse of ADM, and solves the installation difficulties caused by inaccurate borehole depth in actual projects. The ADM with sectional structure can still withstand the pressure of up to 500 MPA, and the segmented plug can be plugged for at least 100,000 times. Advanced ID recognition algorithm is adopted to support the mixed assembly of ADM with different node numbers and lengths.

 

6. Online transmission and real-time analysis. Secondary development, compatible platform.

The ADM applies 4G network to transmit data in real time. The monitoring data is processed online by the cloud platform, and the final results are directly output for users to make statistical analysis. The data logger and cloud monitor software adopted by ADM are completely independently developed by GINTEC, which has 100% mastery of core intellectual property rights and processing algorithms. Our strong independent R & D strength also lays the foundation for the secondary development needs of users.

 

7.  Press down verification to ensure monitoring accuracy

In the process of deep displacement measurement, the ADM is installed in the inclinometer casing that pre-installed in the borehole. The inclinometer casing is deformed by external force, and the deformation of the inclinometer casing is transmitted to the ADM. The ADM sensors output the deformation value and we get the test results. Therefore, the ADM touching to the inner casing wall tightly to make them as one is the prerequisite for accurate measurement. If the ADM cannot touch to the inner casing wall tightly, the deformation of the inclinometer casing will not be accurately transferred to the ADM.

 

During the installation process, with the press down verification function of the press down kit and cloud monitor software, the ADM can be installed in touch with inner wall of Inclinometer casing, the equipment and casing are fully integrated. This design has the following advantages.

(1) The ADM attached to the inner casing wall tightly can ensure the accuracy of monitoring data.

(2) When the inclinometer casing is broken due to geological disasters, the ADM has enough expansion allowance in the inclinometer casing, which can record the whole process of the disaster.

 

Principle explanation of press down verification

Inner state of ADM installing in inclinometer casing with press down kit

 

The tilt angle of ADM in inclinometer casing when pressing down in place

 

As shown in the figure above, the inner diameter of inclinometer casing D is fixed, and the single segment length of ADM L (30cm, 50cm or 100cm) is fixed. After the ADM is pressed in place inside the inclinometer casing, the ADM will support the casing wall along the diameter direction of the inclinometer casing, so the inclination angle of each segment of ADM in the inclinometer casing is a fixed angle  

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