Difference Between An Accelerometer And A Gyroscope

 Accelerometer and gyroscope are two kinds of sensors commonly used in vibration monitoring of structures. They all measure changes in vibration or displacement by sensing changes in an object’s acceleration or angular velocity. But there are some differences in how they work and how they are applied. The following will be a detailed introduction to the role and differences between accelerometers and gyroscopes.

The function and principle of accelerometer

The accelerometer is used to measure acceleration. A triaxial accelerometer can be used to measure the motion of a fixed platform relative to the earth’s surface, but once the platform moves, the situation becomes more complex.  For example, the ER-3QA-02E is a high-performance three-axis accelerometer with digital output, high precision installation error, temperature compensation, and low power consumption.If the platform is free falling, the accelerometer measured the acceleration value is zero. If the platform is moving in a certain direction, the acceleration values of each axis will contain the acceleration value generated by gravity, so that the true acceleration value cannot be obtained. For example, the triaxial accelerometer mounted on the 60-degree roll Angle plane will measure the vertical acceleration value of 2G, whereas in fact the plane’s surface is about 60 degrees. Therefore, using the accelerometer alone cannot keep the aircraft in a fixed course.

The function and principle of gyroscope

Gyroscope measures the rate of rotation of the body around an axis. When the gyroscope is used to measure the rotation Angle of the aircraft’s body axis, if the plane is rotating, the measured value is non-zero, and the value of the measurement is zero when the plane is not rotating. Therefore, the angular velocity value of the gyroscope measured at the 60-degree roll Angle is zero, and the angular rate is zero when the plane is flying in a straight line. The current roll Angle can be estimated by the time integral of the angular velocity value, provided there is no error accumulation. Gyroscope to measure the value of the drift with time, after a few minutes or a few seconds will be the additional error accumulation, and eventually lead to the current relative horizontal roll Angle to the plane completely wrong cognition. Therefore, the use of gyroscopes alone cannot maintain a particular course of the aircraft.

The difference between accelerometers and gyroscopes

Accelerometers and gyroscopes are both sensors used to sense changes in vibration or displacement of structures, but there are some important differences between them.

1. Different measurement methods

The accelerometer mainly measures the linear acceleration of the object, while the gyroscope mainly measures the angular acceleration and angular velocity of the object. Their measurement methods are different, so they are suitable for different vibration test occasions. The high performance quartz flexible accelerometer represented by ER-QA-03A adopts high quality quartz crystal to achieve high precision acceleration measurement and has 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.

2. Different measurement directions

The accelerometer mainly measures the vibration acceleration of the structure in the x, y and z directions, while the gyroscope mainly measures the angular velocity of the object in the x, y and z axes. Therefore, they are suitable for vibration tests that are not coaxial upwards.

3. Different application fields

Accelerometers are mainly used in the field of structural vibration testing, while gyroscopes can be used in a wide range of object motion testing fields, such as drones, aerospace and so on.
In summary, accelerometers and gyroscopes are commonly used sensors for vibration testing of structures and motion testing of objects. They have their own characteristics and application range. Accelerometers are generally more commonly used than gyroscopes in vibration measurement applications, but in the measurement of angular displacement and velocity of objects, gyroscopes are more suitable.

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IMU in Drones

The inertial measurement unit works by detecting the current acceleration using one or more accelerometers. IMUs use one or more gyroscopes to detect changes in rotation properties such as pitch, roll and yaw. Some IMUs on drones include magnetometers, which are primarily used to assist in calibration to prevent directional drift.

Onboard processors constantly calculate the drone’s current position. First, it integrates the perceived acceleration with an estimate of gravity to calculate the current velocity. The velocity is then integrated to calculate the current position.

To fly in any direction, the flight controller collects IMU data for the current position and then sends the new data to the motor Electronic Speed Controller (ESC). These electronic speed controllers send the thrust and speed signals needed for the quadrotor to fly or hover to the motor.

Now, you can have the best 6-axis gyroscope technology, but if your drone hardware (propellers, motors, bearings, shafts, etc.) is not straight, clean, or functioning properly, the drone will still fly irregularly or even crash.

It is always a good idea to inspect the parts of the drone before and after each flight. It’s a good idea to have spare parts in case they crack or bend. Keeping drones clean is another good practice. To check whether the propeller is straight, it is best to have a propeller balancer. If all the components look normal and the drone is flying erratically, put it back immediately.

If the drone flies erratically, recalibrate the IMU on a flat surface. Sometimes you need to calibrate the IMUs multiple times. You should also check the drone manufacturer’s website for firmware updates to address any issues within the flight controller. If there are other problems, then the drone could have a hardware failure in the IMU or flight controller.For example, the ER-MIMU-02 developed by Ericco has high performance and small size;

Gyroscope bias instability: 0.05 degrees/hour. It has a wide range of applications. It can be used not only on drones, but also in many fields such as mining and drilling. If you want to know more about IMU products, please click the link below and contact us.

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What are the Advantages of Accelerometer Sensor?

 The accelerometer senor consists of detection quality (also known as sensitive mass), supports, potentiometers, springs, dampers, and shells. The constraint of the test quality can only be moved along one axis, which is called the input shaft or the sensitive axis. When the instrument shell Accelerates along the sensitive axis as the carrier moves, according to Newton’s law, the detection quality with certain inertia tries to keep its original motion state unchanged.

The relative motion between the accelerometer and the shell will result in the deformation of the spring, so the detection quality accelerates with the effect of the spring force. When the spring force is in equilibrium with the inertia force generated by acceleration of the detection mass, there will be no relative motion between the detection mass and the shell. The deformation of the spring reflects the magnitude of the acceleration measured. The potentiometer, as a displacement sensor, converts the acceleration signal to an electrical signal for output. The accelerometer is essentially an oscillating system with one degree of freedom, and a damper should be used to improve the dynamic quality of the system.

Advantages of acceleration sensors

The acceleration sensor has the characteristics of high precision and high sensitivity. It can accurately measure the acceleration change of the object during the movement and output it as a digital signal. This feature of high precision and high sensitivity. For example, the zero-bias stability of ER-QA-03A is 10-50μg, the scale factor is 15-50 PPM, and the second-order nonlinearity is 10-30μg/g2, which provides accurate data support in the industrial field to help engineers perform accurate motion control and analysis.

The acceleration sensor has the characteristics of small size and light weight. This allows acceleration sensors to be easily installed in a variety of devices and structures without placing too much of a burden on them. The small size and lightweight also mean that acceleration sensors can operate in limited Spaces and have high reliability. The ER-QA-03F is a small accelerometer with a diameter of Φ18.2mm, a scale factor of 150-220 PPM, and a second-order nonlinearity of 40-50μg/g2. For devices with strict space requirements, this accelerometer is a good choice.

Acceleration sensors have a wide operating temperature range. Whether it is in an extremely cold environment or in a high temperature environment, the acceleration sensor can work properly. This makes it possible to use it in extreme conditions, such as aerospace and deep sea exploration. ER-QA-03D can operate normally at a working temperature of -55~180 ° C, and its volume of 25×21mm, impact resistance 500-1000g 0.5ms.

The acceleration sensor has the function of self-diagnosis and fault detection. With internal algorithms and automatic calibration, the accelerometer detects and corrects its own faults, ensuring data accuracy and reliability. This self-diagnosis and fault detection capability helps reduce maintenance costs and increase productivity.

Quartz flexible accelerometer adopts the principle of flexible deformation of quartz material, uses external force to act on the mass of the flexible arm to make it flex, and measures the change of the flex signal to determine the acceleration. Quartz flexible accelerometer has the advantages of high precision, high sensitivity and high stability, but the manufacturing cost is high and the volume is large. MEMS accelerometers use microelectromechanical system technology to measure the acceleration using micro mechanical structure and electronic components. MEMS accelerometers have the advantages of small size, light weight, low power consumption and low cost, but the accuracy and stability are relatively low.

Quartz flexible accelerometers and MEMS accelerometers also have certain differences in application fields. Because the quartz flexible accelerometer has high precision and high stability, it is widely used in high-end fields such as military and aerospace. MEMS accelerometers are widely used in consumer electronics, automotive safety systems, sports bracelets and other fields because of their small size, low power consumption and low cost.

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What are Three Examples of Ways to Use a Tilt Sensor?

 A tilt sensor is a sensor used to measure the tilt angle of an object relative to the horizontal plane. It can accurately and real-time monitor and record the change of tilt angle, which provides important data support for various industrial applications and scientific research fields. 

Today we have three examples of how tilt sensors can be used in application scenarios.

1. Bridge monitoring: Bridge is an important part of urban traffic, and its stability and safety are crucial to the normal operation of the city. In order to ensure the safety of the bridge, it is necessary to monitor its structure in real time. Tilt sensor can be used to monitor the tilt angle of bridge and provide real-time data support for structural safety. By installing tilt sensors at key parts of the bridge, the tilt angle can be continuously monitored and the data can be transmitted to the control center for analysis. Once abnormal conditions are found, timely measures can be taken for maintenance and reinforcement, thus ensuring the safe use of the bridge.

2. Construction machinery

Excavator, in order to realize the three-dimensional spatial positioning of the excavator, on the basis of installing the angle sensors of each joint of the working device, the platform rotation angle detection device and the platform inclination sensor are installed, and the laser receiver is installed on the bucket rod to detect the height of the horizontal mechanism emitted by the ground laser transmitter relative to the zero position of the receiver. The kinematics model of the excavator is established, and the coordinate transformation matrix of the car body relative to the earth is derived, that is, the car body positioning in three-dimensional space is completed, and the commonly used simple car body elevation positioning formula is obtained, so as to realize the three-dimensional space positioning of the excavator's excavation trajectory and lay the foundation for realizing the accuracy of the excavator's three-dimensional space trajectory and the excavator's depth control.

Other heavy industrial machinery - in addition to excavators, in other heavy industrial machinery, including cranes, lifts, graders, etc., will use tilt sensors, and tilt sensors have a heavy and heavy role in these heavy machinery equipment. It not only ensures that the angle range of these mechanical equipment is within the safety, but also can be raised to the alarm if it is out of range to protect personal safety. For example, the inclination sensor in the retractable mechanical hand is to measure the attitude of the cab and the change in the tilt angle of the boom to ensure driving safety.

3. Platform control

Shipborne horizontal platform - The inclination sensor is applied on the shipborne horizontal platform, which is used for shipborne satellite to track the base of the antenna to keep the antenna in a horizontal state at all times, and for real-time control of the platform, which can isolate the pitch and roll motion of the hull and make the platform level.

In addition, the inclination sensor is also applied in the launching process of the ship air bag, and is applied to the hook swing of the large pipe laying ship for monitoring and adjustment.

Application of inclination sensor in automatic levelling system of reference plane of large optoelectronic equipment. The dip angle sensor installed on the base detects the dip angle and direction of the reference plane, converts the angle into the elongation of several mechanical legs according to the leveling algorithm, and drives the elongation of the mechanical legs to make the reference plane level.

Ericco's ER-TS-12200-Modbus and ER-TS-32600-Modbus tilt sensors can be used in bridge monitoring, construction machinery, platform control and other fields.

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How is IMU used in drones?

First of all, we know that the IMU combines a 3-axis accelerometer and a 3-axis gyroscope, which can provide the UAV with the data needed to maintain stable flight, and can be integrated with other systems such as GPS for dead reckoning navigation. Because these functions are so critical, a drone can often use multiple IMUs for greater accuracy and redundancy.

The main reasons include: The IMU can be used as a backup in the event that the drone's other vital navigation systems, such as GPS, are blocked, interrupted or completely disabled. In addition, IMU is also indispensable for applications that cannot use GPS and other similar services at all.

Ericco continues to innovate and research, and has developed a product ER-MIMU-01 that can be used in drones to perform the initial alignment of the drone launch system. ER-MIMU-01ER-MIMU-01 uses high-quality and reliable MEMS accelerometer and gyroscope, RS422 communicates with the outside, the baud rate can be flexibly set between 9600~921600, and the communication baud rate required by the user is set through the communication protocol. 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.

On the other hand, since UAVs adopt vision-based positioning and collision avoidance principles, OIS/EIS can be used as another input that can be used for flight stability.

Drones are also popular for carrying on-board cameras for aerial still pictures and videos. With the help of IMU and OIS/EIS software, any drone can be turned into a high-resolution camera. If you want to know more about imu, please click the link below.

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How does the Inclinometer Sensor Work?

The inclinometer sensor is actually an application of the MEMS accelerometer, which is the principle that the accelerometer can be used to measure the angular velocity of an object in a static state.

The inclinometer sensor’s theory is 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. When the inclinometer sensor is at rest, that is, there is no acceleration in the side and vertical directions, then the only force acting on it is the acceleration of gravity. The angle between the vertical axis of gravity and the sensitive axis of the acceleration sensor is the angle of inclination. The inclinometer sensor in the general sense is static measurement or quasi-static measurement, once there is external acceleration, then the acceleration measured by the acceleration chip contains the external acceleration, so the calculated angle is not accurate, therefore, the common practice is to increase the mems gyro chip, and adopt the preferred Kalman filter algorithm. The ER-TS-3260VO‘s built-in (MEMS) solid pendulum can measure changes in the static gravity field, convert them into changes in inclination, and output them through voltage (0~10V, 0~5V optional), so that the calculated angle is quite accurate.

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How to Distinguish North Finder and Theodolite?

 In the inertial navigation industry, these two instruments It is often used. Let’s talk about the difference between the North Finder and theodolite today.

The north finder is also called the gyro north finder, which is a high-precision dual-axis dynamic tuned gyro. The purpose is to find the true north direction value of the object. Ericco’s ER-MNS-05 (0.25°/1°), it can also be combined. Acceleration is used to measure and correct the horizontal angle, which is mainly used in the fields of borehole directional instrument, drilling equipment control and measurement, marine survey, three-dimensional scanner, radar, antenna, military vehicle and so on. The principle is to determine the true north direction value of the attached carrier autonomously by measuring the angular velocity of the earth’s rotation, without being disturbed and affected by external magnetic fields or other environments. In addition, it can also be combined with acceleration for horizontal angle measurement and correction.

1. Analytical fast north finding principle

The analytical fast north finding is mainly composed of inertial sensor components, horizontal turntable, base (including shock absorber), control circuit and computer. The inertial sensor component is mainly composed of a flexible gyroscope and an accelerometer meter, which is used to sense the angular velocity of the earth’s rotation and the acceleration of gravity.

2. Decomposition of the angular velocity of the earth’s rotation

The earth’s rotation angular velocity (15.0411 degrees/h, 7.29213101e-5rad/s) vector is parallel to the earth’s axis, and the north direction is positive. At any point P on the earth’s surface, the rotation angular velocity at that point can be decomposed into a vertical component and a horizontal component, which is the latitude value of point P. The true north position refers to the direction of the horizontal component of the earth’s rotation angular velocity.

3. The principle of gyro north finding in the horizontal state of the platform

The selected flexible gyro for north-seeking azimuth vertical reference is a dual-axis rate gyro, which has two orthogonal input X, Y and two corresponding output shafts, and the rotor axis is the Z axis. Ericco’s MEMS gyroscope ER-MG2-100 is used for north finding, and the built-in IMU is used for inclination measurement and azimuth calculation.  In order to eliminate the influence of the vertical component, it is always desired that the XY axis of the gyro is in the horizontal plane (or as close as possible to the horizontal state). At this time, the horizontal component of the ground speed sensitive to the two axes is related to the north-seeking angle.

Theodolite is a measuring instrument designed to measure horizontal and vertical angles based on the principle of angle measurement. Its function is to accurately measure the horizontal and vertical angles of the measuring object. It is mostly used in many fields such as construction, road and bridge construction. 

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