Classification and Working Principle of Accelerometer

 

Accelerometer is a device that can measure the acceleration experienced by an object. Acceleration can be defined as the force applied per unit of mass, A=F/m. It is the rate of change of an object’s velocity with respect to time.

There are many types of accelerometers: linear accelerometers (detection mass for linear displacement) and pendulum accelerometers (detection mass rotation around the support shaft) are categorized according to the displacement type of detection quality; gemstone supports and flexible supports are classified according to the support type. , Air flotation, liquid floatation, magnetic levitation, electrostatic suspension, etc.According to the composition of measurement systems, there are open-loop type and closed-loop type; according to the working principle, there are vibrating wire type, oscillating beam type and pendulum type gyro accelerometer; The number of input shafts is classified into uniaxial, biaxial and triaxial accelerometers; they are classified by sensor elements, such as piezoelectric, piezoresistive and potentiometer type. An accelerometer is usually named by combining the features of several different classifications.

There are four types of accelerometers:

1. Piezoelectric accelerometer

Piezoelectric accelerometers work by sending an electrical signal from the sensor when sudden acceleration is encountered. The structure of the piezoelectric accelerometer consists of a sensing crystal on which seismic weights are attached. When the sensor experiences acceleration, the weight exerts a force on the crystal. The piezoelectric crystal converts the force acting on it into an electrical signal that can be measured to find the acceleration. Piezoelectric accelerometers are very effective at measuring shock and vibration.

2.piezoresistive accelerometer

Piezoresistive or piezoresistive accelerometers work by changing their resistance according to the acceleration experienced. Changes in acceleration can be measured to understand the rate of acceleration experienced by the sensor. Piezoresistive accelerometers are not as sensitive as piezoelectric accelerometers because they are not the best at measuring low frequency effects. However, they work best at high amplitudes and have found their applications in vehicle crash testing and weapon testing. Capacitive accelerometers: Capacitive sensors work by changing their capacitance based on the acceleration they experience. Their structure consists of two capacitive plates and a diaphragm. When the sensor experiences acceleration, the diaphragm moves, changing the distance between the capacitor plates. This causes a change in the capacitance of the sensor, and this change in capacitance can be measured and converted into acceleration on the sensor. You’ll find capacitive MEMS(micro-electro-mechanical System) accelerometers in most smartphones today.

3. Capacitive accelerometer

These types of accelerometers sense capacitance changes associated with acceleration. The sensing element of a capacitive accelerometer consists of two parallel-plate capacitors operating in differential mode.
These shunt capacitors operate in a bridge circuit, and they have two fixed capacitors that change the peak voltage produced by the oscillator while the sensor is in an accelerated state. The detection circuit detects the peak voltage, which is fed to the adding amplifier to process the output signal.

4. Three-axis accelerometer

A triaxial accelerometer can measure acceleration in three orthogonal directions (or three vertical planes-x, Y, and Z). This feature enables the three-axis accelerometer to measure all vibration components affecting an object. The triaxial accelerometer consists of three sensing elements that are perpendicular to each other. They can be used to measure building vibrations, turbines and high-speed machinery.

If you want to get more details about quartz-accelerometer,pls visit https://www.ericcointernational.com/accelerometer/quartz-accelerometer/

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Resolution and Accuracy of Tilt Sensors

 

Accuracy and resolution of tilt sensors

Resolution refers to the sensor in the measurement range can detect and resolve the smallest change in the measured value. The accuracy refers to the error between the angle measured by the sensor and the real angle.

The relationship between precision and resolution with examples 

Take the familiar vernier calipers. We often say that the accuracy of the vernier caliper is 0.1mm, in fact, this statement is not correct, it should be said that the resolution of the vernier caliper is 0.1mm. That is, when the change in length is 0.1mm, Can our eyes see it, tell it apart. The accuracy of the vernier caliper, because the accuracy represents the difference between the measured value and the true value, the accuracy is related to many factors. For example, temperature causes thermal expansion and contraction, when we see a change of 0.1mm, the real may be 0.09mm, such as the caliper bending, or the caliper engraving line is not particularly uniform, will lead to poor accuracy, but the resolution is still 0.1mm. To improve the accuracy of the measurement, we must first improve the resolution of the measurement, if the resolution can not be distinguished, then the accuracy from where to start. Resolution is the limit of accuracy, improve the resolution at the same time to eliminate the impact of other factors on the accuracy, in order to effectively improve the final accuracy.

The angle sensor based on acceleration principle is illustrated in detail. It is the measurement of gravitational acceleration on the sensitive axis of the acceleration sensor into angle data, that is, the angle value and the acceleration value into a sine relationship.

The resolution of tilt sensors are also often referred to as sensitivity. It is mainly caused by the noise of the sensor. The noise equivalent angular change is called the angular resolution. Because the size of the noise is related to the frequency response, the higher the frequency response, the greater the noise. The resolution of the sensor can be improved effectively by taking effective measures to suppress the noise. After the resolution is improved, there is a chance to compensate for the adverse impact of other factors on the accuracy.

Other factors affecting the accuracy of tilt sensors

Of course, there are many factors that affect the accuracy of tilt sensors, in addition to the most important resolution, but also include:

Zero bias–depending on the characteristics of the core sensitive device itself, it means that the sensor in the absence of angle input (such as absolute horizontal plane), the sensor measurement output is not zero, the actual output angle value is zero bias.

Nonlinearity— can be corrected later, depending on the number of correction points. The more correction points, the better the nonlinearity.

Horizontal axis 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.

Input shaft non-alignment – refers to the installation deviation of the sensor in the actual installation process, which actually includes the input shaft non-alignment and vertical shaft non-alignment errors.

Sum up

We use specific tilt sensors products to look at the relationship between resolution and accuracy, for example, our ER-TS-12200-Modbus, from the main parameters can be seen, its resolution is 0.0005°, that is, within the measurement range of ±30° can detect and distinguish the smallest change value measured is 0.0005°, the resolution is quite high. The comprehensive accuracy within the full temperature of -40~85° can reach 0.001°, because its resolution has been improved a lot, so its accuracy is naturally improved. 

In the following figure, the main parameters of ER-TS-3160VO Low cost Voltage Type Single Axis Tilt Sensor, in different measurement ranges, its resolution is not the same, at ±10° its resolution can reach 0.001°, the accuracy is 0.01°. By comparing the parameters of these two products, we can see a relationship between resolution and accuracy. The resolution is low, the accuracy is relatively low, if the resolution is improved, the accuracy will be improved accordingly.

What Is A Flexible Pendulum Accelerometer?

 

Quartz flexible accelerometer, as a classic high-precision mechanical pendulum accelerometer, is one of the key components in the field of high-precision applications. Quartz flexible accelerometer has been developed for more than 50 years, it is in the mid-1960s with the development of low-cost inertial navigation system requirements, developed on the basis of mature liquid floating pendulum accelerometer non-liquid floating dry accelerometer. The liquid floating pendulum accelerometer is large, the processing and assembly process requirements are very strict, the sealing requirements are very high, and the cost is high. Because the quartz flexible accelerometer adopts flexible support technology, the structure and process are greatly simplified, and the accuracy and reliability have fully met the application requirements of modern inertial navigation systems, so the production is more widely used.

1.Structural design

Pendulum accelerometer with flexible support.The pendulum assembly is connected with the instrument housing by two flexible rods.The bending stiffness of the flexible bar around the output shaft is very low, while the stiffness in other directions is very high.Its basic working principle is similar to that of a liquid pendulum accelerometer.The system has a high – gain servo amplifier that keeps the pendulum assembly operating near zero.In this way, the bending of the flexible bar is very small and the introduced elastic moment is also small, so the meter can achieve very high accuracy.This type of accelerometer is available in oil filled type and dry type.The oil-filled type is filled with high viscosity liquid as damping liquid, which can improve the dynamic characteristics of the instrument and enhance the anti-vibration and anti-impact ability.The dry accelerometer adopts electromagnetic damping or air film damping, which facilitates miniaturization, reduces costs and shortens startup time, but the accuracy is lower than that of the oil-filled accelerometer.

2.Factors affecting the performance of quartz flexible accelerometer

There are many precise mechanical parts in the quartz flexible accelerometer. As the core part of the accelerometer, the dial head plays a decisive role in the range and performance of the accelerometer. The two indexes of measuring the accuracy of the accelerometer are mainly zero offset value and scale factor stability, which can reflect the comprehensive performance of the accuracy of the accelerometer. Analyzing the influencing factors is very important to improve the accuracy of the accelerometer.

2.1 Stiffness of quartz flexible beam

The pendulum component of the accelerometer is supported by two parallel quartz flexible beams. This design allows the flexible beam to be considered as pure bending when the Angle is shifted, that is, the stiffness is very small in the direction of the input axis and very large in the direction perpendicular to the input direction. When the pendulum component of the accelerometer moves, the capacitor position sensor will detect the offset of the pendulum component, feed back to the meter head circuit and output the feedback current to the torque coil, and the electromagnetic force will make the pendulum component return to the balance position. If the feedback moment or inertia moment is too large or too small, the pendulum component will be twisted. If the bending application cannot bear the torsional moment because of the quartz flexible beam material, the pendulum component will produce angular oscillation of the gas film, which is a very dangerous and destructive phenomenon.

Therefore, the range of quartz flexible pendulum acceleration will be affected by the stiffness of the flexible beam. The flexible beam of the existing accelerometer is designed according to the range standard of ±30g ~ ±60g, and the small-range accelerometer requires much smaller sensitive acceleration and high resolution, so the thickness and width of the flexible beam can be appropriately reduced, thereby reducing the stiffness of the flexible beam.

2.2 Magnetic induction intensity of permanent magnet

The magnetic induction intensity of permanent magnet materials is not constant, and it will be interfered with by various external environments. When the temperature rises, the magnetic induction intensity decreases. On the contrary, the magnetic induction intensity increases. But its variation is nonlinear, its magnetic induction intensity temperature repeatability is very poor, which has a great impact on the overall performance of the torquer. At the same time, the magnetic induction intensity of permanent magnets will also weaken with the change of time. Therefore, the stability of permanent magnet is also a major factor affecting the stability of accelerometer. At the same time, after the permanent magnet is magnetized, its magnetic field can not be changed, which makes the quartz flexible accelerometer relatively poor ability to adapt to the environment. Therefore, in order to improve the accuracy of the accelerometer, it is necessary to improve the design of the torque field.

2.3 Temperature

When the quartz flexible pendulum accelerometer is working, the internal temperature of the accelerometer will increase, and the torque coil will heat itself when passing the feedback current, which will also cause the temperature change of the meter head. Temperature is the main factor affecting the scale factor and zero deviation of quartz flexible pendulum accelerometer. In order to meet the accuracy requirements of the airborne gravimeter for the accelerometer, it is necessary to control the temperature of the accelerometer.

2.4 Damping interference

In quartz flexible pendulum acceleration, air damping is the most important damping, in addition to some electromagnetic damping generated by the torque coil. The formation of electromagnetic damping is because when the pendulum component swings up and down, the magnetic field of the working gap of the torquer will act on the coil of the pendulum component, generating induced voltage and current. Therefore, the internal damping interference is also a factor affecting the resolution of the quartz flexible pendulum accelerometer.

3.Summary

Through the above content, learn about the structural design of the flexible accelerometer and the factors that affect the performance, among many manufacturers, ericco stands out in the market with high-quality accelerometer products, with ER-QA-03A as the representative of high performance, its  bias repeatability is 10-50μg  and  scale factor repeatability is  15-50 ppm ，it is that integrates accuracy and reliability.

contact me :https://www.ericcointernational.com/accelerometer

Email : info@ericcointernational.com

Whats app:+8613992884879

Tilt Sensor Use and Maintenance Precautions

 

What should be paid attention to during the use of the tilt sensor

1. The bending radius of the cable cannot be smaller than 15mm.
2. The tilt sensor should not work in an environment below -40 degrees Celsius for a long time.
3. The tilt sensor connector cannot be disassembled by itself. Contact the manufacturer for advice.
4. Keep the instrument box dry and avoid long-term exposure to sunlight or rain.
5. During use, the battery should avoid excessive discharge and overcharging, so as not to reduce the battery life, and the standard charging time is 10 hours.
6. It should be handled gently during use to prevent violent impact.
7. The storage and transportation process should avoid strong acids and alkalis to prevent corrosion and damage to the instrument.
8. Please read the data stored by the instrument in time to prevent excessive measurement data and overwrite the previous measurement data.
9. The cable should avoid sharp, sharp items in use to prevent cable damage.
10. The sensor is recommended to be returned to the factory for calibration every 3 years.

If the tilt sensor fails in the following faults, you can refer to the following solutions

1. After the product is obtained, if there is no normal output, what inspection and inspection can be done by yourself?

① First immediately turn off the power supply, check whether the working voltage meets the requirements of the manual, and check whether the wiring is correct;

② If there is no problem with the wiring, test the working current of the product, compared with the indicators on the manual, the difference is large, indicating that the product has been damaged;

③ Replace the product to confirm whether the communication line is smooth;

④ Consider whether the communication parameters are correct, such as baud rate, address, output mode, etc.

2. Inclination can not read the command normally, what can you do by yourself?

If the product is used for the first time:

① Ensure that the receiving line of the product is well connected

② Replace the product and confirm whether the communication line is smooth

③ If the product has no angular output at the same time, consider whether the communication parameters are correct, such as baud rate, address, output mode, the above points can not solve the problem, consider the host computer or communication tooling problems; If the product is used after a while, If there is a problem, and the problem disappears by replacing other products, please contact us if there is a problem with the product.

Why does the tilt switch give a false alarm? How to deal with these false alarm tilt switches?

The turbulence of the vehicle or the interference of the surrounding environment will cause the angle information of the tilt switch to change, which will lead to false alarm. Please confirm whether the above two conditions exist and test the product in the absence of the above possible conditions, if they still exist, Please contact us for questions.

The troubleshooting steps are as follows:

1. During the measurement process, if the displacement does not change and the counting button does not respond, please check whether the sensor connector is connected properly.
2. Can not be turned on, please plug in the charger, confirm the battery power is sufficient, if still can not be ruled out, please return to the factory repair.
3. If the battery life is obviously shortened, check whether the battery power is sufficient. If the battery power is sufficient, it indicates that the battery is aging.
4. If data cannot be read when connecting to the upper computer, disconnect the PC, check whether the driver is correctly installed, restart the upper computer, and try to reconnect it, and check whether the USB connector is loose.
5. Inaccurate measurement occurs in the use of the sensor. Please confirm whether the guide wheel and spring are loose and need to be replaced.
6. If the time cannot be saved during the configuration, ensure that the entered time complies with natural laws.
7. The hole information displayed in the configuration cannot be modified. Confirm that the hole is new and no measurement data has been saved.

In summary:

This ER-TS-4150VO sensor belongs to a single-axis wired tilt sensor. Because there are cables, the bending radius of the cable should not be less than 15mm during use. Sharp and sharp objects should be avoided during use to prevent cable damage. Its operating temperature range is -40~+85° C, but it is not suitable to work for a long time in an environment below -40 ° C. If you are using the product for the first time, be sure to ensure that the receiving line of the product is well connected, if there is no problem with the wiring, test the working current of the product, compared with the indicators on the manual, the difference is large, indicating that the product has been damaged. 

The ER-TS-32600-Modbus is a wireless transmission tilt sensor, it is powered by a lithium battery, so the battery should avoid excessive discharge during use, avoid overcharging, so as not to reduce the battery life, the standard charging time is 10 hours. Please read the data stored by the instrument in time to prevent excessive measurement data and overwrite the previous measurement data.   

IMU algorithm: data acquisition & calculation of speed and direction

The IMU algorithm refers to the inertial navigation system algorithm, which is used to estimate the speed and direction of an object based on data collected by inertial sensors (gyros and accelerometers). To use the IMU (Inertial Measurement Unit) algorithm to calculate speed and direction, data from the accelerometer and gyroscope need to be combined. The following will explain in detail the calculation of objects and speeds from collected data and the IMU algorithm.

Data acquisition and speed and direction calculation stepsData collection

The IMU algorithm works based on data collected by gyroscopes and accelerometers. Gyroscopes can measure the rotation speed of an object in three axes, while accelerometers can measure the acceleration of an object in three axes. This data is used to calculate the object’s attitude (pitch, yaw, and roll angles) and velocity.

• Attitude calculation: The IMU algorithm calculates the attitude of the object through gyroscope data. Use quaternions or Euler angles to represent the attitude, and calculate the rotation angle and rotation axis of the object through continuous-time quaternions or Euler angles. By comparing the poses of the current frame and the previous frame, the rotation speed and angular speed of the object in three-dimensional space can be calculated.
• Speed calculation:The IMU algorithm calculates the speed of an object through accelerometer data. Objects will be affected by gravity when they move, and the components of gravity acting in different directions can be expressed as g. Therefore, the gravity component can be calculated from the acceleration measured by the accelerometer, and then the velocity and displacement of the object can be obtained through integration. At the same time, since changes in the attitude of the object will produce changes in inertia, the angular velocity of the object can be obtained through gyroscope data, and the rotation angle and rotation axis of the object can be obtained through integration.
• Fusion algorithm: In order to improve the accuracy and stability of the IMU algorithm, a fusion algorithm can be used to fuse sensor data such as gyroscopes, accelerometers and magnetometers. The fusion algorithm can use algorithms such as Kalman filter, complementary filter or Madgwick filter. By fusing data from different sensors, more accurate speed and direction information can be obtained.

2.Data preprocessing:In order to get more accurate results, you may need to perform some preprocessing on the original data, such as filtering or denoising. This can be achieved with various digital filters such as Kalman filters.

3.Calculate the accelerometer offset: Due to the Earth’s gravity, the accelerometer will read a constant offset even if the device is stationary. To eliminate this offset, the accelerometer’s offset needs to be updated periodically.

4.Calculate the angular velocity deviation:Similarly, the gyroscope may also have an initial deviation due to various reasons (such as errors during startup). This deviation can be estimated by comparing rotation angles over time and updated periodically.

5.Calculate speed and direction: Once you have the bias-corrected acceleration and angular velocity data, you can use these data to calculate speed and direction. For velocity, this can be found by integrating angular velocity; for direction, it can be found by integrating acceleration (but this usually results in cumulative errors, so more sophisticated methods such as magnetometers or GPS assistance may be needed).

6.Compensate for the effects of the Earth’s rotation:The Earth’s rotation also creates a small rotational moment on the device, which affects orientation calculations. To eliminate this effect, it may be necessary to use some method to track the speed of the Earth’s rotation and take this into account when calculating the direction.

7.Integrate other sensor data: To improve accuracy, you can also consider integrating other sensor data, such as magnetometers or GPS. A magnetometer can provide a device’s absolute orientation relative to the Earth’s magnetic field, while GPS can provide a device’s precise location and timestamp, which is particularly useful for long-distance navigation.

Brief description of IMU algorithm

The IMU (Inertial Measurement Unit) algorithm is a complex system used to calculate speed and direction by combining data from accelerometers and gyroscopes. And collect its data and add it to the algorithm to output the attitude angle and speed information of the device. The following is a more detailed IMU algorithm process. This part will explain the above content in more detail.

1.Data collection:

IMUs typically contain accelerometers and gyroscopes. Accelerometers measure acceleration, while gyroscopes measure angular velocity. Data acquisition is accomplished through a microcontroller or computer, which periodically reads and stores the IMU sensor measurements.

2.Data preprocessing:

Due to the existence of noise and outliers, data denoising and filtering are required. Commonly used filters include the Kalman filter in Figure 1 and the complementary filter in Figure 2, which can combine accelerometer and gyroscope data to provide more accurate results.

                                                                                         Figure1: Kalman filter

                                                                                    Figure2:complementary filter

3.Accelerometer deviation compensation:

The accelerometer is affected by the Earth’s gravity when stationary, which causes a fixed bias in the measurement results. By comparing acceleration measurements over time, this bias can be estimated and compensated for.

4.Gyroscope deviation compensation:

The gyroscope may have an initial bias when it starts up, which affects the angular velocity it measures. This deviation can be estimated and compensated for by comparing angular velocity measurements over time.

5.Speed calculation:

Use integrated angular velocity to calculate the angle of rotation. By integrating the angular velocity twice, you get the velocity. This requires knowing the initial velocity and initial position.

6.Direction calculation:

Use integrated acceleration to calculate direction. But this approach can lead to cumulative errors because the Earth’s rotation affects the device’s orientation. To improve accuracy, corrections can be made in conjunction with data from other sensors such as magnetometers or GPS. A magnetometer can provide a device’s absolute orientation relative to the Earth’s magnetic field, while GPS can provide a device’s precise location and timestamp.

7.Kalman filter application:

The Kalman filter (Figure 1) is an optimization algorithm used to combine data from multiple sensors to provide more accurate results. It uses mathematical models to predict sensor measurements and updates the predictions with new measurements. In IMU applications, the Kalman filter can be used to fuse accelerometer and gyroscope data to provide more accurate attitude angle (pitch, yaw and roll angle) and velocity information.

• Pitch angle θ (pitch): rotates around the X-axis.
• Yaw angle ψ (yaw): Angle of rotation around the Z-axis.
• Roll angle Φ (roll): The angle of rotation around the Y axis.

                                                                                       Attitude angle diagram

8.Output:

After the above steps, the IMU algorithm can output the attitude angle and speed information of the device. This information can be used in a variety of applications such as drone control, robot navigation, and motion tracking.

It should be noted that the implementation of the IMU algorithm involves complex mathematical operations and sensor fusion technology. In actual applications, further adjustments and optimizations may be required to adapt to different application scenarios and hardware devices.

Conclusion：

The above article briefly describes a detailed algorithm of IMU from data collection to speed and direction calculation. Through the processing and analysis of gyroscope and accelerometer data, the attitude, speed and direction information of the object can be obtained. In order to improve the accuracy and stability of the algorithm, a fusion algorithm can be used to fuse multiple sensor data. It is through this method that Ericco Inertial System. calculates the speed and direction of the IMU, which can more accurately measure the direction of the object. Your company is also constantly developing independently higher-precision IMUs. So far, ERICCO has developed Two types of IMU: MEMS IMU and FOG IMU. For example, the navigation-level ER-MIMU01 and ER-MIMU05 can independently seek north without relying on a magnetometer or GNSS. The accuracy of the gyroscope is also relatively high, the angular velocity random walk is less than 0.005, and the bias stability is less than 0.1°/h. Compared with other companies’ products, it has great advantages and higher accuracy.

ERICCO’s MEMS IMUs are divided into navigation-level and tactical-level. Compared with many top-ranking system companies, the biggest advantage of navigation-level IMUs is that they can independently seek north, which many large companies cannot achieve with MEMS IMUs. And they better reflect the inherent characteristics of MEMS IMU: small size, high performance, low cost, light weight and other characteristics. The most important thing is that these characteristics allow them to be produced in large quantities. This is relatively friendly to customers with high demand. If you want to know more about or purchase IMU products, please contact our technical staff.

Contact me：

Website：https://www.ericcointernational.com/inertial-measurement-units

Email: info@ericcointernational.com

WhatsApp: +8613992884879

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

 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.

1. Bridge monitoring

Bridges are an important part of urban traffic, and their 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. For example, ER-TS-3160VO can be installed in the key part of the bridge to monitor the change of the tilt angle of the bridge, its accuracy is 0.01°, the measurement range is 0~±180°, and the measured value can be output by 0~10V, 0.5~4.5V, 0~5V voltage, which is very suitable for bridge, dam and other monitoring projects.

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 tilt sensor in the retractable robot arm is used to measure the attitude of the cab and the change of the tilt angle of the boom to ensure driving safety. ER-TS-4258CU has strong resistance to external electromagnetic interference and is suitable for long-term work in harsh industrial environments. It can be installed in the retractable arm of the construction machinery, and can measure the attitude of the cab and the tilt angle of the boom in real time, which can ensure the driving safety to the greatest extent.

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.  

Resolution and Accuracy of Tilt Sensors

Accuracy and resolution of tilt sensors

Resolution refers to the sensor in the measurement range can detect and resolve the smallest change in the measured value. The accuracy refers to the error between the angle measured by the sensor and the real angle.

The relationship between precision and resolution with examples 

Take the familiar vernier calipers. We often say that the accuracy of the vernier caliper is 0.1mm, in fact, this statement is not correct, it should be said that the resolution of the vernier caliper is 0.1mm. That is, when the change in length is 0.1mm, Can our eyes see it, tell it apart. The accuracy of the vernier caliper, because the accuracy represents the difference between the measured value and the true value, the accuracy is related to many factors. For example, temperature causes thermal expansion and contraction, when we see a change of 0.1mm, the real may be 0.09mm, such as the caliper bending, or the caliper engraving line is not particularly uniform, will lead to poor accuracy, but the resolution is still 0.1mm. To improve the accuracy of the measurement, we must first improve the resolution of the measurement, if the resolution can not be distinguished, then the accuracy from where to start. Resolution is the limit of accuracy, improve the resolution at the same time to eliminate the impact of other factors on the accuracy, in order to effectively improve the final accuracy.

The angle sensor based on acceleration principle is illustrated in detail. It is the measurement of gravitational acceleration on the sensitive axis of the acceleration sensor into angle data, that is, the angle value and the acceleration value into a sine relationship.

The resolution of tilt sensors are also often referred to as sensitivity. It is mainly caused by the noise of the sensor. The noise equivalent angular change is called the angular resolution. Because the size of the noise is related to the frequency response, the higher the frequency response, the greater the noise. The resolution of the sensor can be improved effectively by taking effective measures to suppress the noise. After the resolution is improved, there is a chance to compensate for the adverse impact of other factors on the accuracy.

Other factors affecting the accuracy of tilt sensors

Of course, there are many factors that affect the accuracy of tilt sensors, in addition to the most important resolution, but also include:

Zero bias–depending on the characteristics of the core sensitive device itself, it means that the sensor in the absence of angle input (such as absolute horizontal plane), the sensor measurement output is not zero, the actual output angle value is zero bias.

Nonlinearity— can be corrected later, depending on the number of correction points. The more correction points, the better the nonlinearity.

Horizontal axis 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.

Input shaft non-alignment – refers to the installation deviation of the sensor in the actual installation process, which actually includes the input shaft non-alignment and vertical shaft non-alignment errors.

Sum up

We use specific tilt sensors products to look at the relationship between resolution and accuracy, for example, our ER-TS-12200-Modbus, from the main parameters can be seen, its resolution is 0.0005°, that is, within the measurement range of ±30° can detect and distinguish the smallest change value measured is 0.0005°, the resolution is quite high. The comprehensive accuracy within the full temperature of -40~85° can reach 0.001°, because its resolution has been improved a lot, so its accuracy is naturally improved. 

In the following figure, the main parameters of ER-TS-3160VO Low cost Voltage Type Single Axis Tilt Sensor, in different measurement ranges, its resolution is not the same, at ±10° its resolution can reach 0.001°, the accuracy is 0.01°. By comparing the parameters of these two products, we can see a relationship between resolution and accuracy. The resolution is low, the accuracy is relatively low, if the resolution is improved, the accuracy will be improved accordingly.