What are the Methods of North Finding?

 Definition of north finding

The definition of north finding is to find true north, not magnetic north, and the north seeking methods mentioned in this article are all described closely around true north.

True north refers to the Earth’s north pole, which is the intersection of 90° north latitude or the meridian. It is also known as true north. It is the direction that passes through a point on the Earth and points toward the Earth’s geographical north pole. The tangent direction of the true meridian passing through a certain point on the earth’s surface becomes the true meridian direction of that point.

Magnetic north is the north indicated by a compass, primarily because the poles of the Earth’s magnetic field do not coincide with the geographic north and south poles. Therefore, the north indicated by a compass is magnetic north, not true north, and magnetic north changes over time.

North finding uses a gyroscope to measure the component of the earth’s rotation angular velocity combined with the acceleration value, and then calculates the angle with true north to obtain the azimuth angle value.

The methods of north finding

North seeking mainly includes two north seeking methods: static north seeking and dynamic north seeking. The application principles of these two north seeking methods are introduced below.

Principle of static north finding

Static north seeker includes MEMS gyro north seeker and fiber optic gyro north finder.

Principle: The rotation axis of the gyroscope maintains a constant direction relative to the inertial space, while the Earth rotates around the polar axis relative to the inertial space at its rotational angular velocity. If you use the Earth as a reference, you will see that the gyroscope’s axis of rotation rotates relative to the Earth, so the gyroscope can track and measure the angular velocity of the Earth’s rotation.

MEMS gyro north seeker, which has an input axis and a rotation axis. The sensor includes a motor drive structure, a motor signal output from the motor drive structure, a gyroscope, and a sensor rate for the sensor rate signal output from the gyroscope.

Fiber optic gyro north seekers are mainly used to quickly and autonomously determine the true north direction. The Earth’s rotation angular velocity is obtained through high-precision fiber optic gyroscope tracking, and the Earth’s rotation angular velocity signal is decomposed and solved to calculate the angle between the gyroscope’s main axis and the Earth’s true north to provide the carrier with orientation information.

Principles of dynamic north finding

Dynamic north seeking includes fiber optic gyro compass and fiber optic gyro compass (vehicle, ship, airborne)

Principle: Use the strapdown compass effect to find the direction of true north.

The fiber optic gyro compass consists of: three-axis dynamically adjustable gyroscope, three-axis acceleration sensor, data acquisition and processing module, secondary power supply, optocoupler isolated input and output serial port circuit and other related structural parts.

With so many methods available, they are suitable for different circumstances and are not one-size-fits-all. For north seekers used in most fields, inertial measurement device FOG north seekers and MEMS north seekers are relatively advanced in technology.

Comparison of various gyro north seeking systems

By comparing two gyro north-seeking systems, we discovered the similarities and differences between the static north-seeking method and the dynamic north-seeking method.

Common points:

1.They all use the precession and axis fixation of the gyroscope to be sensitive to the earth’s rotation angular speed.

2.The working principle uses the characteristics of the edge of the gyro chamber, that is, the effect of gravity.

Differences:

1.Theoretical differences

The gyroscopic north seeker uses the output of the gyroscope and accelerometer to calculate its azimuth relative to true north to achieve north seeking. Compared with gyro azimuth and gyro compass, it has the advantage of fast north finding speed. However, during the process of north seeking, due to the short start time of the gyro when the gyro north seeker seeks north, there is a gyro drift trend term that is difficult to eliminate, and this term gradually decreases as the gyro starts. The time increases, so the length of time the gyroscope is activated when the north-seeking instrument seeks north has a great influence on its north-seeking accuracy.

2.Differences in application scenarios

Gyrocompasses are mainly used for navigation, such as ships, submarines, UAVs, weapon systems and reconnaissance platforms, providing high-precision azimuth, attitude, navigation and control information. The ER-FGC-2C high-precision gyrocompass has the characteristics of small size, good stability, and high precision, and is fully suitable for navigation in ships, submarines, drones, etc.

Gyro theodolite is mainly used for measurement of large-scale projects such as mines and tunnels. The gyroscope part provides accurate azimuth reference. At the same time, gyro-theodolite can also be used for weapon system aiming.

Gyro-theodolite has high north-finding accuracy, but it cannot be used on mobile carriers such as airplanes and ships because the suspended gyroscope is suspended from the instrument box with a flexible metal belt. On a moving carrier, the instrument shell moves with the carrier. Severe vibrations will cause the flexible metal belt to loosen and fail to maintain a tight state, causing the gyroscope’s movement to lose its original pattern and become unable to work.

3.Differences in performance features (north seeking time and north seeking accuracy)

The north seeking time of the gyro north seeker is short, generally within 5 minutes, and the accuracy can reach about 0.1’. At the same time, there are very few north seekers that can achieve this level of accuracy. ERICCO’s ER-FNS-02 high-precision FOG north seeker has an accuracy of (0.02°-0.1°) and is used for high-precision initial alignment and direction control solutions, which provides a lot of convenience for work. Accuracy can improve relatively over time. The north-finding time of a gyro-theodolite generally takes about 5 to 20 minutes, and the accuracy can reach 10”.

Most recommended north finding equipment

Through the analysis of the two types of north seeking methods, the most suitable north seeking tools for us to use in most fields are MEMS north seekers, FOG north seekers, etc.

The fiber optic gyroscope north seeker uses a closed-loop fiber optic gyroscope as the core component. It is mainly composed of an inertial measurement unit (IMU), a digital signal processing unit and a mechanical part. Provides true north azimuth for the carrier.

The ER-MNS-06 MEMS north seeker is the world’s smallest three-axis MEMS north seeker. It consists of a three-axis MEMS gyroscope and an accelerometer and can measure true north. It has the characteristics of small size, light weight, low power consumption and resistance to harsh mechanical environments, and is widely used in mining, tunnel construction and other fields.

When choosing the most appropriate north-finding device, both gyro-theodolite and gyro-north-finder achieve north-finding on a static basis. Therefore, we can start from the respective characteristics of these two types of devices and complement each other in research or use to achieve coordination of north-seeking accuracy and north-seeking speed.

This article introduces the brief knowledge of the north-finding method. I hope you have a basic and clear understanding of the north-seeking method. If you want to know more about north seeking, you can find useful content in “More Technical Questions”. If you are interested in north finder related products, you can click on “Products in article”. For any questions, please leave your opinions in ‘Ask a Question’ below.

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Tilt Sensor Test Bridge Deflection

Tilt sensors measure bridge deflection is applicable to the deflection test of any bridge span length at any position, and belongs to the field of bridge detection technology, in particular, it relates to a high-precision and high-efficiency bridge deflection test method in the process of bridge detection.

Background technique

In bridge testing, it is necessary to measure the deflection of the bridge, and the accuracy of the deflection measurement data is directly related to the assessment of the bridge state. Meanwhile, the timeliness of the bridge testing is required. Therefore, in the process of bridge inspection, the high precision and high efficiency bridge deflection testing system is very important. In the prior art, the field test of bridge deflection generally adopts the following methods: 1.Optical measuring instruments such as level are used to measure bridge deflection. Although the operation is simple, the measurement accuracy is low, and the measurement results are greatly affected by human influence and interference, which cannot be applied to the test of bridge dynamic deflection and the error is large. 2.The use of dial meters, dial meters and other displacement meters to test the bridge deflection, the scaffolding needs to be set up below the beam body, so as to install the deflection test instrument on the scaffold, but in the scaffolding under the bridge, there is a complex process, time-consuming and laborious, and higher scaffolding has a greater safety risk, its own shaking and uneven settlement at the bottom will affect the test results of bridge deflection. 3.The use of photoelectric image principle, through the acquisition of image signals, the use of data processing method, to obtain the deflection value of the bridge, its working principle is complex, image data acquisition is limited by weather, light and other specific conditions, data processing is complex, and the cost is high, the accuracy is low, the actual operability is poor. 4.Based on the principle of connecting pipe, the deflection of bridge is directly measured according to the change of liquid level in the open connecting pipe. This method is simple in principle, but due to the viscous resistance between liquid and pipe wall and the capillary action between water and pipe wall, the test accuracy is not high, and it cannot be applied to the test of dynamic deflection of bridge.

Therefore, the existing bridge deflection testing device has the following defects: 1.Low test accuracy and large error; 2.The test device installation is complicated, the data collection is more complicated, the labor cost is high, the work efficiency is low; 3.It cannot be applied to the detection of dynamic deflection of Bridges and the deflection of bridges across large rivers and grand canyon.

How do inclinometer measure bridge deflection?

Tilt sensor measurement of bridge deflection is a bridge deflection test method based on dip angle, which converts the dip angle change of bridge section into the change of bridge deflection. In other words, the inclinometers is arranged in 5 sections of the bridge to measure the angle of section. The (electrical) signal of the change of dip angle is timely transmitted to the acquisition system through signal cables, and the mathematical relationship formula between bridge deflection and dip angle is calculated by using the dip angle value of section. And then calculate the deflection at any one position.

For example, if we want to measure the deflection of a bridge at any position, we place an ER-TS-4258CU current type biaxial tilt sensor at this position of the bridge, so that the tilt sensor of the 5 sections can be measured, and the signal of the inclinometer change is transmitted to the data acquisition system in real time through the current. We can use the dip value measured by the tilt sensor of the section arrangement to calculate the mathematical relationship between the deflection and the dip angle of the bridge, and then calculate the deflection that needs to be measured at the bridge position.

The disturbance is, in layman’s terms, the amount of deformation. The disturbance of the steel structure such as the cantilever beam should meet the corresponding specifications. The deformation should not be too large, and the formula of the material mechanics can be used for calculation. The deflection of the bridge has a corresponding relationship with the corner angle of the section. The deflection of the bridge can be measured by a double-axis inclination sensor mounted on the bridge. The method uses the structural finite element model to calculate the deflection curve of the unit load acting at different positions. The deflection curve is used as the reference displacement mode, and the true deflection is the linear combination of the reference displacement modes. The combination coefficient is determined by using the minimum inclination test data. The method of two-square fitting effectively reduces the influence of test errors.

Summary: The tilt sensor measure bridge deflection is easy to operate and the test data are accurate, the measurement efficiency is high, and the performance is stable and reliable, and it is not affected by the change of bridge structure form and bridge section. It can solve the problems such as the difficulty of deflection testing and the poor accuracy of measurement data of bridges spanning large rivers and grand canyon.

Do you Know the Working Principle of Inclinometer ?

 The working principle of inclinometer

Let me briefly introduce the inclinometer commonly used in petroleum logging, which is a kind of in-situ monitoring instrument for measuring the dip angle and azimuth of borehole. The required data can be obtained through all kinds of sensor components in the survey sensor, and then the data can be recorded from the high-temperature memory to obtain the relevant azimuth angle, dip angle, temperature data, depth, tool face angle and other parameters that engineers want to know, so as to determine the specific situation of the drilling.

In foreign countries, inclinometer has been used for position monitoring in earth dam, roadbed, slope and tunnel and other geotechnical engineering since 1950s. Our country began to introduce inclinometer sensors from the United States, Japan, Britain and other foreign countries and monitor some important geotechnical engineering in the 1980s. In order to better develop the exploration of oil, coal, offshore oil well development of China’s research and development in this area is also as a large project to carry out, and some related research institutions developed resistance strain type, accelerometer type and electronic meter type and other intelligent inclinometer.

Up to now, various inclinometers have been widely used in the fields of water conservancy and hydropower, mineral metallurgy, transportation and geotechnical engineering for urban construction, and have played an important role in ensuring the safety of geotechnical engineering design, construction and use.

Inclinometer application fileds: borehole survey, foundation pit, foundation, wall, dam slope, oil field logging, marine logging exploration, coal mine exploration, etc.

How does the inclinometer work?

Working principle of inclinometer when measuring angle probe from bottom to top in the dip tube piecewise sliding when measuring, the probe’s sensor is sensitive to reflect the dip tube in the angle changes in the depth of each segment, and then according to the tilt angle and the horizontal displacement at different elevation of the incremental, from the bottom of the dip tube station began to piecewise accumulative, can get the horizontal displacement at any height, when the inclinometer observation, in order to eliminate and reduce the zero drift and assembly error of the instrument, the data should be measured and read once in the positive direction of displacement and in the opposite direction after the probe turns 180 degrees, and the algebraic average value of the measured data in the positive and negative directions should be taken as the measurement value of inclination.

Designed based on the principle ER-TS-12200-Modbus high precision wireless transmission tilt senor  is a wireless inclination sensor with ultra-low power consumption, small size and high performance, which is aimed at the industrial application of users without power supply or real-time dynamic measurement of object attitude angle. Powered by lithium battery, based on Internet of things technology Bluetooth and ZigBee (optional) wireless transmission technology, all internal circuits have been optimized and designed, and various measures such as industrial MCU, three proof PCB board, imported cable, wide temperature metal shell are adopted to improve the industrial level of the product. With good long-term stability and small zero drift, it can automatically enter the low-power sleep mode, so as to get rid of the dependence on the use environment.

The product has compact structure, precise design, re compensation for temperature and linearity, and integrated comprehensive protection functions such as short circuit, instantaneous high voltage, polarity, surge, etc. It is simple and convenient to use. The wireless digital signal transmission method eliminates the cumbersome wiring and noise interference caused by long cable transmission; The industrial design has extremely high measurement accuracy and anti-interference ability. The wireless sensor nodes can form a huge wireless network, support thousands of measuring points to monitor the inclination at the same time, and support professional computer software. Without field survey, it can measure and record the state of the measured object in real time; The safety monitoring system is suitable for remote real-time monitoring and analysis of industrial sites, dilapidated houses, ancient buildings, civil engineering, tilt deformation of various towers and other needs.

How is IMU used?

 The concept of IMU

 

The inertial measurement unit, referred to as IMU, is a device that measures the three-axis attitude angle (or angular velocity core) and acceleration of an object. Gyroscopes and speedometers are devices of an inertial navigation system.

With the built-in speed sensor and gyroscope, the IMU can measure linear acceleration and rotational angular velocity from three directions, and can obtain information such as the vehicle's attitude, speed, and torsion through calculation.

IMU working principle

 

The IMU is a module composed of various sensors such as a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer.

1. The working principle of three-axis accelerometer

 

Most three-axis acceleration sensors use piezoresistive, piezoelectric and capacitive working principles. The acceleration generated is proportional to changes in resistance, voltage and capacitance, and is collected through corresponding amplification and filtering circuits. This is based on the same principle as the ordinary acceleration sensor, so with certain technology, three single axes can be turned into a three-axis. For most sensor applications, two-axis acceleration sensors can already meet most applications.

2. The working principle of three-axis gyroscope

 

The working principle of the three-axis gyroscope is based on the gyroscopic effect. When the gyroscope's axis of rotation is perpendicular to the direction of a force, it will feel the effect of the force, thereby generating a torque that causes it to rotate in the coordinate system. The three gyroscopes in the three-axis gyroscope are installed on three mutually perpendicular axes. They sense the angular velocity on the x, y, and z axes respectively, and output the signals to the relevant circuits for processing.

3. The working principle of three-axis magnetometer

 

The magnetometer uses three mutually perpendicular magnetoresistive sensors. The sensor in each axis detects the strength of the geomagnetic field in that direction. For example, alloy materials with some crystal structures. They are very sensitive to external magnetic fields, and changes in the strength of the magnetic field will cause changes in the resistance value of the magnetoresistive sensor. In addition, the three-axis magnetometer can also use the Lorentz force principle. The current flows through the magnetic field to generate force, thereby driving changes in capacitance and so on.

Application of high performance quartz accelerometer

 

Inertial navigation IMU has a wide range of application scenarios and is often used for pointing, steering and guidance in advanced mining/drilling equipment, ships, automobiles, drones, robots, oil exploration, bridge exploration, high-rise buildings, iron towers, dam monitoring, rock Soil monitoring, navigation and positioning of transportation vehicles such as mining and missiles, and north-finding positioning in geodetic/land mobile mapping systems.

 In the aviation field, inertial navigation IMU can realize motion control of aircraft such as climbing, descending, turning and taxiing, improving flight safety and accuracy.

In the automotive field, inertial navigation IMU can help vehicles achieve autonomous driving and traffic jam identification, improving driving performance and safety.

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Is a Tilt Sensor the Same as as an Accelerometer?

 Different concept

Tilt sensor is a tool for measuring various angle changes. It is usually divided into single axis, dual axis, wireless transmission tilt sensors, etc.

Acceleration sensor is a device that can measure acceleration force. The accelerating force is the force that acts on an object as it accelerates, just like the Earth’s gravity, which is gravity. The accelerating force can be a constant, like g, or it can be a variable. There are two kinds of accelerometers: one is an angular accelerometer, which is modified by a gyroscope (angular velocity sensor). The other is a linear accelerometer.

Different working principles

Tilt sensors are based on Newton’s second law: according to the basic principles of physics, inside a system, velocity cannot be measured, but acceleration can be measured. If the initial speed is known, the line speed can be calculated by integrating, and then the linear displacement can be calculated, so it is actually an acceleration sensor using the principle of inertia. For example, the ER-TS-3168CU tilt sensor, which uses the principle of inertia and built-in accelerometer, can measure the angular speed at rest, and can calculate the line speed through integration, which can accurately compensate and correct the temperature error and linear error. It has the characteristics of high precision, small size, high packaging process, strong impact resistance, anti-vibration ability, built-in anti-RF, anti-electromagnetic interference circuit, etc., especially suitable for the application of underground trenchless machinery and other harsh industrial environment. When the tilt sensor is stationary, that is, there is no acceleration in the side and vertical directions, then there is only gravity acceleration acting on it, and the angle between the vertical axis of gravity and the sensitive axis of the acceleration sensor is the tilt angle. The ER-TS-12200-Modbus wireless inclination sensor can directly measure the inclination angle of the carrier when it is stationary. It has the characteristics of ultra-low power consumption, small size and high performance, and is suitable for remote real-time monitoring and analysis of the needs of industrial sites, dangerous houses, ancient buildings, civil engineering, and various towers’ inclination deformation.

The working principle of the accelerometer: The accelerometer is composed of an upper capacitor, a middle capacitor board (movable), and a lower capacitor board. When the acceleration reaches a certain value, the middle capacitor plate will move, and the distance from the upper and lower capacitor plates will change, and the upper and lower capacitors will therefore change. The capacitance change is proportional to the acceleration. After the output voltage is digitally processed, the digital signal is output.

Different application areas

As a kind of detection tool, inclination sensor has become an indispensable and important measurement tool in bridge erection, railway laying, civil engineering, oil drilling, aviation and navigation, industrial automation, intelligent platform, machining and other fields.

Accelerometers can be used in steel mast structures, bridges or building structures. It can also be used to protect hard drives from damage, as well as in medical and sports equipment, cameras and camcorders, smartphones, remote controls, controllers and navigation systems.

Conclusion: The inclination sensor is the MCU, MEMS accelerometer (MEMS accelerometer is only one component of the inclination sensor integrated circuit board), analog-to-digital conversion circuit, and communication unit are all integrated on a very small circuit board, which can directly output angle tilt data, so that people can use it more conveniently.

Smallest Size Triaxial MEMS North Seeker

 ER-MNS-06 (0.25°-1°):

1. Smallest Size MEMS north seeker in the world;
2. Resistant to harsh mechanical environment;
3. Light weight, low power consumption.

ER-MNS-06 MEMS North Seeker is the world’s smallest triaxial MEMS north seeker, which is composed of a three-axis MEMS gyroscope and accelerometer, can measure the true north. It has the characteristics of small size, light weight, low power consumption, resistance to harsh mechanical environment, and is widely used in mining, tunnel construction and other fields.

Technical Features

Smallest size MEMS north seeker in the world

Triaxial MEMS gyro and accelerometer

Light weight, low power consumption

Resistant to harsh mechanical environment

If you need a north seeker, you can send your needs directly to the email . We will send the price and catalog to you！
E-mail：info@ericcointernational.com

What is the use of imu?

IMUs are often included in inertial navigation systems that use raw IMU measurements to calculate orientation, angular velocities, linear velocity, and position relative to a global reference frame. IMU-equipped INS form the basis for navigation and control of many commercial and military vehicles such as manned aircraft, missiles, ships, submarines and satellites. IMUs are also important command and control components for unmanned systems such as UAVs, UGVs and UUVs. Simpler versions of INS, called attitude and heading systems, use the IMU to calculate the vehicle's heading position relative to magnetic north. Data collected from the IMU sensors allows the computer to track the ship's position using a method known as dead reckoning.https://www.ericcointernational.com/inertial-measurement-units

In land vehicles, the IMU can be integrated into GPS-based automotive navigation systems or vehicle tracking systems, giving the system dead-reckoning capabilities and the ability to collect as much accurate data as possible about the vehicle's current speed, turn rate, heading, and lean. and acceleration in combination with the vehicle's wheel speed sensor output and, if available, the reverse signal, for purposes such as better traffic accident analysis.

In addition to navigation purposes, IMUs serve as orientation sensors in many consumer products. Almost all smartphones and tablets contain IMUs as orientation sensors. Fitness trackers and other wearable devices may also include IMUs to measure movements such as running. IMUs also have the ability to detect people's developmental levels during movement, determining the specificity and sensitivity of specific running-related parameters. Some gaming systems, such as remote controls for the Nintendo Wii, use the IMU to measure motion. Low-cost IMUs have fueled the rapid growth of the consumer drone industry. They are also often used in sports technology (technical training)[4] and animation applications. It is a competing technology for use in motion capture technology.[5] The IMU is at the heart of the balancing technology used in the Segway personal transporter.

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