What is the Principle of Inertial Measurement Unit?

Introduction to IMU

An inertial measurement unit is a device that measures the three-axis angular velocity and acceleration of an object. In a narrow sense, an IMU is equipped with gyroscopes and accelerometers on three orthogonal axes, with a total of 6 degrees of freedom, to measure the angular velocity and acceleration of objects in three-dimensional space. This is what we know as a "6-axis IMU"; in a broad sense, The IMU can add a magnetometer to the accelerometer and gyroscope, forming a "9-axis IMU".

 

Accelerometer: detects acceleration signals of three independent axes of the carrier coordinate system;

Gyroscope: detects the angular velocity signal of the carrier relative to the navigation coordinate system;

Magnetometer: Use algorithms such as Kalman or complementary filtering to provide users with absolute reference pitch angles, roll angles and heading angles.

 

The 9-axis sensor with added magnetometer is also called AHRS (Attitude and Heading Reference System). Because the heading angle has a reference to the geomagnetic field, it will not drift. However, the geomagnetic field is very weak and is often interfered by surrounding objects with magnetic fields. The more orthogonal the magnetic field and gravity field are, the better the attitude measurement effect will be. That is to say, if the magnetic field and gravity field are parallel, such as the geomagnetic north and south poles, AHRS cannot be used.

How an accelerometer works

An accelerometer is a sensor that measures acceleration. Accelerometers manufactured by traditional mechanical processing methods are large in size, mass, and cost, and their applications are greatly limited. With the development of Micro Electro Mechanical System (Micro Electro Mechanical System) technology, the development of micro accelerometers has been regarded as a priority project for the productization of Micro Electro Mechanical Systems at home and abroad. Compared with ordinary accelerometers, microaccelerometers have many advantages: small size, light weight, low cost, low power consumption, good reliability, etc. It can be widely used in aerospace, automotive industry, industrial automation and robotics and other fields, and has broad application prospects.

The essence of an accelerometer is to detect force rather than acceleration, that is, the detection device of the accelerometer captures the inertial force that causes acceleration, and then Newton's second law can be used to obtain the acceleration value. The measuring principle can be represented by a simple mass, spring and indicator.

The accelerometer adopts the "Northeast Sky" coordinate system (ENU): g = (0, 0, −9.81) T g= (0, 0, -9.81)^T g= (0, 0, −9.81) T.

 

An accelerometer is a sensor that measures acceleration. It usually consists of mass block, damper, elastic element, sensitive element and adjustment circuit. During the acceleration process, the sensor uses Newton's second law to obtain the acceleration value by measuring the inertial force exerted on the mass block. The structure includes a silicon diaphragm, an upper cover, and a lower cover. The diaphragm is between the upper cover and the lower cover and is bonded together. One-dimensional or two-dimensional nanomaterials, gold electrodes and leads are distributed on the diaphragm, and a pressure welding process is used to lead out the leads. Depending on the sensor sensitive components, common acceleration sensors include capacitive, piezoresistive, piezoelectric, etc.

How gyroscopes work

When a particle moves in a straight line relative to the inertial system, its trajectory is a curve relative to the rotating system due to its own inertia. Based on the rotation system, we believe that there is a force driving the movement trajectory of the particle to form a curve. The Coriolis force is a description of this deflection, expressed as:

That is to say, when the linear motion is placed in a rotating system, the linear trajectory will deviate. In fact, the linear motion problem is not affected by a force. The establishment of such a virtual force is called the Coriolis force.

Therefore, we select two objects in the gyroscope. They are in constant motion, and the phase difference of their movements is -180 degrees. That is, the two mass blocks move in opposite directions but have the same size. The Coriolis forces they generate are opposite, thus forcing the two corresponding capacitor plates to move, resulting in a differential change in capacitance. The change in capacitance is proportional to the angular velocity of rotation. The change in rotation angle can be obtained from the capacitance.

The measurement accuracy of the IMU is mainly determined by the gyroscope used, so the gyroscope is the core component of the navigation system.

How a magnetometer works

A magnetometer is a device that uses the earth's magnetic field to determine the North Pole. The magnetometer can provide data on the magnetic field experienced by the device in each of the XYZ axes. The relevant data is then imported into the microcontroller's processor to provide the heading angle related to the magnetic north pole. This information can be used to detect geographical orientation. The magnetometer uses three mutually perpendicular magnetoresistive sensors. The sensor in each axis detects the strength of the geomagnetic field in that direction.

The picture above shows an alloy material with a crystal structure. 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.

 

The above article briefly describes the principle of IMU. The MEMS IMU developed by ERICCO has the advantages of low cost, low consumption, high performance and light weight. It is very popular among customers. If you want to buy an IMU, please contact our professionals.

The Application of Accelerometer in Aircraft

 The accelerometer uses high quality quartz crystals to achieve high precision acceleration measurement with extremely high reliability and stability. Its special flexible construction enables it to adapt to high acceleration applications under various environmental conditions, such as high temperature, high pressure and high vibration environments.

Accelerometers are an important part of aircraft, which can help control the attitude and stability of aircraft, helicopters, drones, etc. Accelerometer technology can detect the acceleration of the position to find out whether other aircraft are running over the aircraft, so that the aircraft can correct the deviation in time and maintain stability.

The attitude indication system on the aircraft mainly refers to the instrument system that accurately measures and indicates the attitude of the aircraft, which provides the pitch Angle, roll Angle and yaw Angle for the pilot and other on-board electronic products (such as flight guidance system, automatic flight control system and radar, etc.). The traditional attitude indication system is mainly composed of horizon instrument aircraft, turning instrument and sidering-slip instrument, with large size, cumbersome structure and weak accuracy. The digital attitude indication system widely used today uses high-precision gyro and accelerometer, with greatly improved accuracy. However, because the traditional high-precision gyro has weak overload carrying capacity, large size and expensive price, its application scenario is greatly limited. The Ericco accelerometer ER-QA-01A, specially designed for aviation applications, is not only small in size but also has a bias repeatability of 10μg, a proportional coefficient repeatability of 10 PPM, and a Class II nonlinear repeatability of 10μg/g². The high precision navigation MEMS gyroscope ER-MG2-300/400 is capable of meeting the measurement range of ±400°/s, 0.05°°/hr bias instability and 0.025°/√hr Angle random walk, in addition to the strict requirements for accuracy and carrier space size in the aviation field, compared to other products of the same type. Or other advantages.

The principle of the angular accelerometer is similar to that of an accelerometer. Its outer box is mounted on a rotating object. Due to the angular acceleration, a tangential dynamic load is generated on the reference mass, and a signal proportional to the magnitude of the tangential acceleration or the angular acceleration can be output. With different measured moving objects and measurement requirements, accelerometers have various principles and implementations. For example, on the aircraft, there are gyro accelerometers designed according to the gyro principle.

Measure the acceleration of the carrier line. An accelerometer that measures aircraft overload is one of the first aircraft instruments to be applied. Accelerometers are also commonly used on aircraft to monitor engine failure and fatigue damage of aircraft structures. Accelerometers are important tools for investigating flutter and fatigue life of aircraft in flight tests of various types of aircraft. In a flight control system, an accelerometer is an important dynamic characteristic correction element. In inertial navigation systems, a high-precision accelerometer is one of the most basic sensitive components. The accelerometers used in different occasions vary greatly in performance. A high-precision inertial navigation system requires the resolution of the accelerometer to be as high as 0.001 g, but the range is not large; an accelerometer for measuring an aircraft overload may require a 10 g range, and the accuracy The demand is not high.

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Which Indicators Affect the Installation and Measurement Accuracy of tilt sensor

 

Tilt sensor accuracy

Tilt sensor is used to measure the object relative to the horizontal tilt angle, in the platform leveling, mechanical manufacturing, safety protection, precision measurement and many other fields have a wide range of applications, manufacturers are also many, but the market face of the accuracy of the inclination sensor understanding is unclear or even biased.

First define the accuracy of the tilt sensor: accuracy refers to the error between the angle measured by the sensor and the true angle. This error is usually defined as the mean square error. That is, the root mean square value between the results of multiple measurements and the true value.

Indicators that affect accuracy

We take the tilt sensor of the acceleration sensing principle as an example. The acceleration sensor converts the component of gravity acceleration measured on the sensitive axis of the acceleration sensor into angle data, that is, the inclination value and the acceleration value are sinusoidal.

Where g represents the gravitational acceleration, a represents the inclination value measured by the acceleration sensor, and α is the inclination angle.

The measurement accuracy of the tilt sensor is closely related to the following indicators:

Noise – depends on the core sensitive device’s own characteristics, but at the same time associated with the frequency response, also known as amplitude frequency characteristics. Generally speaking, the higher the frequency response, the greater the noise. Noise determines the resolution of the sensor, and if the angle change is so small that the change is almost submerged in the noise and cannot be resolved, we consider the angle change to be the resolution of the tilt sensor. For example, the ER-TS-12200-Modbus, its resolution is 0.0005°, because its frequency response is not high, the angle change is very small, and the noise is very small.

The zero bias stability depends on the characteristics of the core sensitive device, which means that when the sensor has no angle input (such as absolute horizontal plane), the measured output of the sensor is not zero, and the actual output angle value is zero bias. The effect of zero bias on the accuracy of the sensor is not terrible, because the zero bias can be eliminated by calibration, but the zero bias usually drifts with time and temperature changes, the drift is called the zero bias stability, and this drift is usually difficult to eliminate, so the drift will cause the accuracy to deteriorate.

Nonlinearity – can be corrected later, depending on the number of correction points. The more correction points, the better the nonlinearity. Although the nonlinear can be corrected by the subsequent correction method, the nonlinear also has the phenomenon of drift, and the drift can not be eliminated, resulting in the deterioration of accuracy.

Cross-coupling error – refers to the error caused by coupling to the output signal of the sensor when the sensor applies a certain acceleration perpendicular to its sensitive axis or tilts at a certain angle. For example, for the wireless tilt sensor ER-TS-22800 with a measuring range of ±30° (assuming that the X direction is the inclination direction), when the space is tilted 10° perpendicular to the X direction (at this time, the actual tilt angle of the measured X direction remains unchanged, such as +5°), the output signal of the sensor will cause additional errors due to this 10° tilt. This error is called cross-coupling error. This extra error varies depending on the product. When the cross-coupling error of the inclination sensor is 3%FS(FS: full scale, full range), the additional error generated is 3%x10°=0.3°, and the actual output angle of the sensor is simply estimated to be 5.3°(=5°+0.3°). At this time, even if the nonlinear error of the inclination sensor reaches 0.01°, compared with the cross-coupling error, this nonlinear error can be ignored, that is, as the measurement accuracy of the inclination sensor, the cross-coupling error cannot be counted, otherwise it will cause a large measurement error.

Installation error – When the sensor is installed and measured, the measuring shaft should be reconnected with the sensor’s sensitive shaft. However, in the actual installation and measurement, it is always impossible to accurately match. For example, if the angle between the installation measuring shaft and the sensor’s sensitive shaft is 1 degree, the measured value is the projection of the actual angle change on the sensitive shaft. If the angle change is 30 degrees, the measured value is 30*cos(0.1)=29.995 degrees, the error is 0.005 degrees, so for high-precision applications, it is very important to keep the measurement shaft and the sensor sensitive shaft match.

Repeated measurement accuracy – depends on the core sensitive device’s own characteristics and cannot be improved by subsequent corrective measures.

The effect of temperature on zero point and sensitivity – also includes drift and repeatability of the temperature curve, which depends on the own characteristics of the core sensitive device and cannot be improved by subsequent correction measures. In the case of repeatability, it can be corrected later, depending on the number of correction points (angle points and temperature points). The more correction points, the better the temperature drift accuracy.

Range – Because the relationship between inclination measurement and acceleration is sinusoidal, the angle measurement error and acceleration measurement error meet the following relationship:

Where da is the inclination measurement error and da is the acceleration measurement error. When the range is close to 90 degrees, the acceleration a is close to the gravitational acceleration g, which is close to infinity, so a slight acceleration error causes a large inclination measurement error.

It can be seen that the systematic error of the inclination sensor contains the repeatability of noise zero deviation and temperature drift, which cannot be corrected and compensated, while the random error contains the cross-coupling error of the input axis non-aligned nonlinear temperature linearity which can be corrected

Positive-sum compensation measures to improve. Therefore, the measurement accuracy of the inclination sensor must not be measured only by nonlinearity, and it is necessary to synthesize the systematic error and random error of the sensor.

Therefore, the accuracy error of the inclination sensor should include nonlinearity, repeatability, noise, zero bias drift, zero nonlinear drift and cross-coupling error.  

What is the Effect of Temperature Coefficient on Quartz Accelerometer?

 Quartz accelerometers, as one of the commonly used accelerometers, are mainly used to measure the acceleration of the carrier, it is a very important inertial device in the market.In the navigation and positioning of various carriers, the trajectory of the object can be obtained by measuring the acceleration, speed or position. However, because only the acceleration can be measured inside the moving object, the quartz accelerometer has a very important significance for inertial navigation technology.

The role of temperature coefficient

These core components are affected by temperature in practical applications, mainly in two aspects: first, the inertia device itself is sensitive to temperature, and the second is the device is affected by the surrounding temperature, that is, the temperature and the heat around the shell will cause errors within the device. The thermal expansion and cold contraction of the material will cause the deformation of the instrument structure parts, and the physical parameters of various internal materials will change accordingly, which directly affects the output stability, and then affects the navigation accuracy of the whole system. For this purpose, the ER-QA-03D can meet the normal operation in the operating temperature of -55℃ -180 ℃, and its offset repeatability reaches 50μg – 250μg, and the scale factor repeatability is 80 ppm – 250 ppm.

Temperature coefficient

Among the many indicators to measure the performance of quartz accelerometer, the stability of its offset value and scale factor are very important performance indicators, and also the prerequisite to ensure the high stability of quartz flexible accelerometer and even the high stability of inertial system. We know that the accuracy of inertial navigation system depends largely on the accuracy of inertial devices. The error of inertial navigation system is also formed by the accumulation of the error of inertial components in time, especially the inertial navigation system that needs to work continuously for a long time, the system error caused by the error of inertial components is astonishing.

Bias temperature coefficient

The offset value is the output value when the input acceleration of the quartz accelerometer is zero, and the change of the bias with temperature is called the offset temperature coefficient. The size and stability of the offset value is an important guarantee for the high linearity of the quartz accelerometer, especially when measuring small acceleration, the stability of the offset value is particularly important. The bias temperature coefficient of conventional accelerometers is about 30 ~ 100μg/℃. With the miniaturization of the inertial system and the requirement of low power consumption, the requirement of bias temperature coefficient is < 10 μg/℃ or even higher is put forward for the accelerometer. For example, the ER-QA-03A1 bias temperature coefficient can reach the range of < 10μg /℃, and the bias repeatability is ≤10μg and the scale factor repeatability is ≤15ppm. Based on the analysis and determination of the internal structure and properties of the material, the stability of the partial value affected by temperature is improved by the temperature compensating technology.

Scale factor temperature coefficient

The scale factor and its stability will directly affect the measuring accuracy of the accelerometer. Since the scale factor is determined by the common formula K1= = ml/Ktg, it is generally believed that ml (pendulum) and Ktg (torque coefficient of the torquer) are two factors that affect the change of the scale factor.It can be seen that the output scale factor is determined by the pendulum and the torque coefficient of the pendulum component. Because the quartz material is used, the thermal expansion coefficient is small, so the impact on the pendulum is small.In order to ensure the long-term repeatability of the scale factor of the quartz accelerometer, it is required to use high-performance permanent magnet materials. For the permanent magnet material used in the torquer, in fact, its stability largely depends on the stability of the magnetic system in various environments (including high temperature, low temperature, variable temperature, shock, overload, etc.). At present, the stability and repeatability of permanent magnet torquers and pendulum components are improved by screening more suitable permanent magnet materials combined with aging process.

From the above statement, it is not difficult to see the influence of temperature on the long-term stability of the quartz accelerometer. With the further study of the temperature coefficient of the offset value and scale factor, we can start from the relevant process technology to reduce the influence of temperature coefficient on the stability, so as to achieve the purpose of more accurate application of the quartz accelerometer.

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IMU working principle & Tactical grade IMU product recommendations

Nowadays, (Micro-electromechanical Systems, MEMS) inertial sensors and inertial systems have become an indispensable development direction of future navigation technology. MEMS technology has been widely used due to its advantages such as small size, light weight, low power consumption, low cost, and impact resistance. At present, the development of MEMS inertial technology is relatively mature. It forms a combined system with auxiliary systems such as gyroscopes and accelerometers, which can provide appropriate solutions for most navigation applications. The Inertial Measurement Unit developed by Ericco are divided into MEMS IMU and FOG IMU. MEMS inertial measurement units are divided into tactical grade and navigation grade. Navigation-level IMUs can independently seek north, while tactical-level Inertial Measurement Units can rely on magnetometers or GNSS to find north. The following will be divided into two parts: an introduction to the working principle of the inertial measurement unit and a product introduction of ERICCO’s tactical-level IMUs.

How the MEMS Inertial Measurement Unit works: 

The inertial measurement unit is a device that measures the three-axis attitude angle (or angular rate) and acceleration of an object. Generally, an inertial measurement unit contains three single-axis accelerometers and three single-axis gyroscopes. The accelerometer detects the acceleration signals of the object in three independent axes of the carrier coordinate system, while the gyroscope detects the angular velocity signal of the carrier relative to the navigation coordinate system. Measure the angular velocity and acceleration of the object in three-dimensional space, and use this to calculate the attitude of the object. It has very important application value in navigation. IMUs are mostly used in equipment that require motion control, such as cars and robots. It is also used in situations where precise displacement calculations using attitude are required, such as inertial navigation equipment for submarines, aircraft, missiles and spacecraft.

The principle of an inertial measurement unit is very similar to taking small steps in the dark. In the dark, due to the error between your estimate of the step length and the actual distance traveled, as you take more and more steps, the difference between your estimated position and the actual position will become farther and farther. When taking the first step, the estimated position is relatively close to the actual position; but as the number of steps increases, the difference between the estimated position and the actual position becomes larger and larger. This method is extended to three dimensions, which is the principle of the inertial measurement unit.

The academic expression is: Based on Newton’s laws of mechanics, by measuring the acceleration of the carrier in the inertial reference system, integrating it over time, and transforming it into the navigation coordinate system, the velocity in the navigation coordinate system can be obtained. , yaw angle and position information.

Therefore, in layman’s terms, the inertial measurement unit is a strapdown inertial navigation system. The system consists of three acceleration sensors and three angular velocity sensors (gyros). The accelerometer is used to feel the acceleration component relative to the vertical line of the ground. The speed sensor is used to get a feel for the angle information.

It is worth noting that the inertial measurement unit provides relative positioning information. Its function is to measure the movement route of the object relative to the starting point, so it cannot provide information about your specific location. Therefore, it is often combined with GPS. Used together, when the GPS signal is weak in certain places, the IMU can play its role, allowing the car to continue to obtain absolute position information and not get “lost.”

ERICCO tactical grade inertial measurement unit

Next, we will mainly learn about a new inertial measurement unit – ERICCO INERTIAL SYSTEM tactical-grade inertial measurement unit: ER-MIMU03（High Precision Navigation/Stable Control MEMS IMU）.

ERICCO launches a tactical-grade inertial measurement unit (IMU): ER-MIMU03 uses high-quality and reliable MEMS accelerometers and gyroscopes. Equipped with X, Y, Z three-axis precision gyroscope, X, Y, Z three-axis accelerometer, with high resolution, it can output the original hexadecimal complement of X, Y, Z three-axis gyroscope and accelerometer through RS422 code data (including gyroscope hexadecimal complement) numerical temperature, angle, accelerometer hexadecimal temperature, acceleration hexadecimal complement); it can also output gyroscope and accelerometer data that have been processed by underlying calculations Floating point dimensionless value. ). The IMU has a built-in acceleration sensor and gyroscope, which can measure linear acceleration and rotational angular velocity in three directions, and obtain the attitude, speed and displacement information of the carrier through analysis. Applications for this tactical-grade IMU include azimuth, attitude, position measurement and maintenance in GNSS-assisted INS. Heading, pitch, roll measurement in UAV AHRS Robot control and control Autonomous machines, unmanned vehicle directional stabilization and control satellite antenna pointing, target tracking system Guidance, navigation and control attitude and attitude IMU in tactical MEMS weapon systems The azimuth angle is maintained and positioned. Movement investigation and maintenance in MRU and other application areas.

High Precision Navigation/Stable Control MEMS IMU integrates a three-axis MEMS accelerometer and a three-axis MEMS gyroscope in a unique redundant design, which can maximize performance while reducing device size.

In terms of performance specifications, the High Precision Navigation/Stable Control MEMS IMU has an excellent gyroscope and accelerometer. The bias instability of the gyroscope is 0.3°/h. Enables long-term dead reckoning and maintains excellent heading performance. The MEMS sensor in ER-MIMU03 has extremely low vibration correction errors and can withstand high vibration environments up to 6.06g.

With very low gyro bias instability, the navigation performance of High Precision Navigation/Stable Control MEMS IMU can work well when GNSS is interfered with or has no signal. This tactical-grade IMU has relatively high accuracy compared to tactical-grade IMUs from other peer companies. If you want to purchase our IMU, please contact our relevant personnel.

Knowledge about Accelerometer

 Accelerometer is an instrument  that uses Newton’s second law (Law of inertia) for measuring the acceleration of the carrier line. The accelerometer is one of the first aircraft instruments to be used for measuring aircraft overload. Accelerometer consists of test quality (also known as sensitive mass), support, potentiometer, spring, damper and shell. Accelerometer is commonly used to monitor engine failures and fatigue damage of aircraft structures.The performance levels of different kinds of inertial accelerometers can be divided into navigation level, tactical level and consumer level.

Development of quartz accelerometers

Accelerometers originated in the 1940s, many new accelerometers appeared in the 1950s, and further improved in miniaturization, low cost, multi-function and high stability in the 1960s, MEMS accelerometers were born and became a technological development trend in the late 1970s, and quantum accelerometers began to be developed in the early 21st century. Become a representative of the future ultra-high precision accelerometer.

Application characteristics

The accelerometer is an important part of the inertial measurement unit (IMU), and together with the gyroscope determines the accuracy of more than 90% of the inertial navigation system, its cost, size, weight and power consumption characteristics on the inertial navigation system (INS) application field also has a greater impact, different application fields have different requirements for the use of the accelerometer.

In the flight control system, accelerometer is an important dynamic characteristic correction element.In inertial navigation system, the high precision accelerometer is one of the most basic sensitive components.The accelerometer in different use situations is different in performance. The high precision inertial navigation system requires the accelerometer to have a resolution of 0.001g, but the range is not large. An accelerometer that measures an aircraft’s overload may require a range of 10g, while the accuracy is not high.For example, ER-QA-03A has bias repeatability of 10-50μg, scale factor repeatability of 15-50 PPM and Class II non-linearity repeatability of 10-30μg/g2 with a resolution of 5μg, so it is a good choice for flight control systems.

In the field of oil and gas drilling, the complex formation structure and the continuous upgrading of drilling technology put forward higher requirements for drilling tools. When measuring the attitude parameters of the steering drilling tool, the tool rotation, near-bit vibration and downhole high temperature and pressure will seriously affect the measurement accuracy of the tool attitude parameters. In order to better overcome these factors to obtain accurate measurement data information, ER-QA-03D can not only meet the temperature environment of -40℃ -180 ℃,  anti-shock is 500-1000g 0.5ms, but also bias repeatability  has 50μg – 250μg .

Key technology

Flexible bracing

The function of flexible support is to convert the change of input acceleration into the change of vibration force of the beam, and then into the change of output frequency. Generally, quartz materials with good strength, high fatigue strength, non-magnetic and good processing ability are used. The design of flexible support combined with the process can be used flat bridge type or arc type. As the key parts of quartz vibration beam accelerometer, the thickness, stiffness and symmetry of flexible joint machining have an impact on the accuracy of the instrument.

Temperature compensation

Temperature is an important aspect that affects the accuracy of quartz accelerometer. The fluctuation of the operating temperature inside the inertial device and the heat source around the shell will cause the error of the output data. The thermal expansion and contraction of the material will deform the structural parts of the accelerometer, and the temperature change will also cause certain changes in the physical parameters of various materials inside the device. The change of the magnetic properties of the torquer will also directly affect the measurement accuracy of the accelerometer. Therefore, through the technology of temperature compensation, the accuracy of the accelerometer can be improved to a certain extent.

Through the above content, we have a preliminary understanding of the related knowledge of the accelerometer other information, for more information, please feel free to contact info@ericcointernational.com

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What is the Difference between Single, Double, Three axis in Tilt Sensor

 

Axial and spatial dimensions of tilt sensors

The conventional spatial dimension is composed of length, width and height, and the inclination sensor can measure the inclination angle of these three dimensions. Therefore, the inclination sensor can be divided into single axis, two axis and three axis according to the axis. Single-axis tilt sensor can only measure the angle of a certain azimuth; The biaxial tilt sensor can measure the angle of two perpendicular azimuths. The three-axis can measure the angle of transformation of the three directions around the arbitrary axis in three-dimensional space.

Single axis, double axis, triple axis 

Inclination sensors usually refer to single-axis tilt sensors, and the theoretical basis of single-axis inclination sensors is 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 velocity is known, the linear velocity can be calculated from the integral, and thus the linear displacement can be calculated. So it’s actually an acceleration sensor that uses the basic principles of inertia. The dual-axis inclination sensor is based on the single axis combined with specific practical requirements, designed and conceived a measurement tool for the angle between two directions.

Based on the direct measurement of the acceleration of the measured object, the biaxial inclination sensor can obtain the linear velocity of the object through integral calculation, and then further obtain the displacement of the object. In essence, the inclination sensor is still an inertial sensor, which follows the inertia law of object motion and the integral calculation method. The two-axis sensor is designed in view of this basic principle, in addition to other measurement principles and measurement methods.

In short, the dual-axis in tilt sensor has the measurement advantages of the single-axis inclination sensor, but also has the measurement effect that can not be achieved by the single axis, with an increasingly wide measurement range. However, the accuracy of the dual-axis inclination sensor is not as good as that of the single axis, and it should be noted that the dual-axis inclination sensor can measure the angle of the X-axis and the Y-axis, but can not measure the X-axis and the Y-axis at the same time, only one axial angle can be measured at a time, the X-axis or the Y-axis, if measured at the same time, it will cause the horizontal axis error and cannot determine its value. Depending on the desired measurement data, you can choose different tilt sensors. In theory, if there are three dimensions of angle change, you need to use a three-axis inclination sensor, but in reality, the three-axis inclination sensor does not exist, more accurately, the two-axis inclination sensor can measure the three-dimensional angle change, without using the so-called “three-axis inclination sensor.” As for why there is no three-axis inclination sensor, it is because when the inclination angle of a incline plane and the X and Y axes is determined, the incline plane is fixed, and there is no possibility of change, that is, the angle between the Z axis is also a definite value.

Taking the X-axis uniaxial tilt sensor as an example, the measuring surface of the sensor can only have an angle with the X-axis, and the inclination plane is fixed on one axis (Y-axis) for rotation. Similarly, the Y-axis uniaxial inclination sensor rotates with the X-axis as the fixed axis. The inclination plane of the biaxial inclination sensor can have an angle with both the X and Y axes, or only one of the axes can have an angle, which is the general case of the inclination plane of the biaxial inclination sensor.

From the above comparative data analysis of the uniaxial and biaxial inclination sensors, it can be seen that the active part of the inclination plane of the biaxial inclination sensor is a point or line, while the single axis can only be a line. For example, the inclination of the vertical wall is the active part of the combination line between the wall and the foundation, which can be measured by the single-axis inclination sensor ER-TS-3160VO; The process of slow toppling of a vertical rod is based on the contact point as the active part, so it is necessary to use the dual-axis inclination sensor ER-TS-4250VO for measurement. In fact, in the process of tilting the vertical rod, no matter which direction it tilts, one thing is certain, that is, the angle between the tilting position and the original position is the angle between the tilting plane and the horizontal plane, this angle may only be a single X or Y axis inclination, or both, which is why it can only be measured with a dual-axis inclination sensor.