What Are The Components Of Accelerometers?

 Quartz accelerometer is a device that uses the piezoelectric effect of quartz crystal to measure acceleration. Quartz accelerometer has the characteristics of high precision, high stability and fast response, and has been widely used in space vehicle, navigation system, earthquake monitoring and other fields.

The structure of quartz accelerometer

Quartz accelerometers are generally composed of quartz crystals, mass blocks and electrodes. The quartz crystal is used as the core component of the sensor, the mass block is used to sense the acceleration, and the electrode is used to measure the piezoelectric charge. Quartz crystals usually have a biaxial symmetrical structure and are composed of two piezoelectric crystal sheets. The piezoelectric axes of the two wafers are perpendicular to each other, allowing acceleration to be measured in any direction. The mass block is attached to the center of the quartz crystal, and when acceleration occurs, the mass block will move relative to the crystal, causing the crystal to produce pressure.

Electrodes are mounted on the surface of a quartz crystal and are used to measure the piezoelectric charge. When the crystal is subjected to pressure, the distribution of positive and negative charges inside the crystal changes, and positive and negative charges accumulate on the electrode, forming a potential difference. By measuring the potential difference on the electrode, the magnitude of the acceleration can be obtained indirectly.

Housing (fixed to the measured object), reference quality, sensitive components, signal output, etc. Accelerometers require a certain range and accuracy, sensitivity, etc. These requirements are often contradictory to some extent. Accelerometers based on different principles have different ranges (from a few g to hundreds of thousands of g), and their sensitivities to sudden acceleration frequencies are also different. The principles underlying common accelerometers are:

① The reference mass is connected to the housing by a spring (see figure). The relative displacement between it and the housing reflects the magnitude of the acceleration component. This signal is output as a voltage through a potentiometer;

② The reference mass is fixedly connected with the elastic thin rod and the shell. The dynamic load caused by the acceleration deforms the rod. The magnitude of the deformation is induced by the strain resistance wire. The output is an electrical signal proportional to the size of the acceleration disc;

③ The reference mass is fixedly connected to the housing through the piezoelectric element. The dynamic load of the mass generates pressure on the piezoelectric element. The piezoelectric element outputs an electrical signal proportional to the pressure or acceleration component:

④ The reference mass is connected to the case by a spring and placed inside the coil. The displacement reflecting the magnitude of the acceleration component changes the inductance of the coil, thereby outputting an electrical signal proportional to the acceleration. In addition, there are servo-type accelerometers, in which a feedback loop is introduced to improve the accuracy of the measurement. In order to measure the acceleration vector in a plane or space, two or three accelerometers are required, each measuring an acceleration component.

In the navigation system, the quartz accelerometer can be used to measure the acceleration of vehicles such as cars and aircraft, so as to achieve inertial navigation and positioning.

In earthquake monitoring, quartz accelerometers can be used to measure the acceleration of seismic waves, so as to study the occurrence mechanism of earthquakes and predict the risk of earthquakes.

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How to Correctly Select the Parameters of the Tilt Sensor

You need to choose your own tilt sensor according to your own needs.

Basic parameters of tilt sensor

1. Range

The range is the maximum range that can be measured by the sensor, which refers to the value of the difference between the upper and lower limits. Each sensor has its own measurement range, and when it is measured in this range, the output signal of the sensor has a certain accuracy. An acceleration sensor with a range of less than 1G is used as an inclination sensor, and a range of more than 1G is used as an acceleration sensor or vibration sensor. Because the larger the range, the less accurate. The biaxial tilt sensor ER-TS-4250VO can be selected in a range of +90°, while the uniaxial tilt sensor can be selected in a vertical direction of 360°.

2. Accuracy

In the process of testing and measurement, measurement errors are inevitable. There are two kinds of errors: systematic error and random error. The causes of system error, such as the inherent error of measurement principle and algorithm, inaccurate calibration, environmental temperature influence, material defects, etc., can be used to reflect the degree of influence of system error. The cause of random error is the gap of transmission components, aging of electronic components, etc. The precision can be used to reflect the influence of random error. Precision is a comprehensive index that reflects systematic error and random error, the higher the precision means the higher the accuracy and precision.

3. Zero offset

Zero drift means that when the input of the sensor is constant zero, the output value of the sensor will still change slightly to a certain extent. There are many reasons for zero drift, such as the change of the characteristics of the sensitive elements in the sensor with time, stress release, element aging, charge leakage, environmental temperature changes, etc. Among them, the zero drift caused by ambient temperature change is the most common phenomenon.

4. Input frequency

The frequency response characteristics determine the frequency range to be measured, and must allow the frequency range without losing the true measurement conditions, in fact, the sensor response will always have a certain delay. The higher the frequency response of the sensor, the wider the frequency range of the signal that can be measured, and the greater the interference. The lower the sensor frequency response, the narrower the frequency range of the signal that can be measured, and the lower the interference. In practical applications, a large number of measured signals are time changes, such as changes in current value, changes in object displacement, changes in acceleration, etc. This requires that the output of the sensor not only accurately reflect the size being measured, but also keep up with the speed of change being measured. In the frequency response range of the sensor, the amplitude of its output has a small change in the -constant range (maximum attenuation is 0.707). Therefore, when the input value is done sine

When changing, it is usually believed that the output value can correctly reflect the input value, but when the input value changes more frequently, the output value will produce significant attenuation, resulting in large measurement distortion.

5. Communication interface

RS232, TTL, RS485, RS232, CAN bus, voltage, current, SPI, IC, Profibus interface optional.If you want to learn more about tilt sensors or buy

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Application of Accelerometer in Vibration Detection

 Whether it is in consumer electronics, industrial automation or automotive applications, when monitoring the operating status and health status of the equipment, it is necessary to select the appropriate sensor according to the operation scenario of the equipment to ensure that the sensor can accurately obtain the information of the equipment, and detect, diagnose and even predict the fault.

Vibration detection is a practical measurement method. The detected vibration data is the key predictive variable for fault diagnosis. Accelerometer is a commonly used vibration detection sensor, widely used in consumer electronics, industrial automation, automotive sensing and other fields, it can collect the status information of a single device or the entire system, and then provide sensor data to facilitate the system to predict the state of the device or system.

With the rapid development of sensors, MEMS accelerometers have become the first choice for everyone. From the current products on the market, MEMS accelerometers are basically taking a capacitive route. This is because the piezoelectric MEMS accelerometer is supported internally by a rigid body. In general, it can only sense dynamic acceleration, but not static acceleration, so the application is limited. Capacitive MEMS accelerometers can detect both dynamic and static acceleration.       

Quartz flexible accelerometer is a kind of precision inertial sensor which can detect the acceleration by sensitive quartz pendulum relative position change. The speed and position of the system can be accurately obtained by calculation, and the accurate acceleration measurement signal can be provided for the navigation, guidance, control and adjustment of various systems. It has been widely used in aerospace, aviation, ships, weapons, petroleum, geotechnical engineering and many other fields. Among them, the precision performance of quartz accelerometer products launched by ericco can reach the middle and high navigation level. Take ER-QA-03A as an example. its bias repeatability is 10-50μg,scale factor repeatability is 15-50 PPM and class II non-linearity repeatability is. Its bias repeatability is 10-50μg,scale factor repeatability is 15-50 PPM and class II non-linearity repeatability is 10 to 30 mu g/g2.

 Therefore, the accelerometer plays a very prominent role in vibration detection, with the improvement of the technology and accuracy of the accelerometer. In the future, accelerometers will be more widely used in the field of vibration detection.       

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How to choose MEMS IMU?

IMU (Inertial Measurement Unit) is an inertial measurement unit that can measure the three-axis acceleration and angular velocity of an object. It is generally used in the measurement part of the system to estimate the pose of the object. IMU generally includes a three-axis accelerometer and a three-axis gyroscope. The accelerometer detects the acceleration signal of the object on three independent axes of the carrier coordinate system, and the gyroscope detects the angular velocity signal of the carrier relative to the navigation coordinate system. The angular velocity and acceleration in space can solve the pose of the object. MEMS IMU is cheap and small, and is widely used in many fields such as navigation, drones, VR, robots, and smart bracelets. The detection accuracy of the IMU is very important to the overall performance of the system. If the noise detected by the IMU is very noisy, then the feedback the system gets is wrong, just like human eyes, ears and other sense organs get wrong information. How can we move freely? The bottom layer of the system is the foundation. If the bottom layer of the system is unstable, it will be difficult for the upper layer to function well. ERICCO has always strictly controlled the accuracy of IMU and has been pursuing the improvement of IMU system. Next, ERICCO will also launch new high-precision IMU products.

1. Zero bias temperature hysteresis characteristics

The zero-bias temperature hysteresis characteristic means that the corresponding zero-bias of the IMU is inconsistent during the heating phase and the cooling phase. Some IMU data manuals will give the zero-bias temperature hysteresis characteristic curve, and some will not. It is best to test it when applying the IMU. Since the IMU zero bias estimate is calibrated based on temperature (the IMU calibration algorithm is introduced in detail), if the temperature lag difference is not too large, the calibration accuracy will be relatively high; if the IMU zero bias hysteresis value is too large, the IMU zero calibration error will be relatively high. large, thus affecting the fusion effect.

2.Vibration characteristics

In the case of external vibration, the variation characteristics of IMU deviation with vibration frequency. Some MEMS IMU chips have abnormal frequency characteristics under high-frequency excitation. For applications such as rotor drones that are prone to high-frequency vibrations, vibration characteristics are generally tested. If the IMU frequency characteristics are abnormal, you can consider it. Add shock absorbers.

3. Effect of repeated power-on on IMU deviation

Ideally, it is thought that under the same external conditions, the bias of the IMU will remain the same each time it is powered up. In fact, under the same external conditions, the bias of the IMU will be different every time the IMU is powered up. If the difference is relatively large, it will be zero. The bias estimation error will be relatively large, affecting the fusion effect.

4. The impact of stress on prejudice

The influence of stress on IMU includes: the influence of stress moment on offset, and the influence of different stresses on offset. The stress mainly comes from: the stress exerted by the PCB board on the IMU chip and the stress exerted by the temperature control device on the IMU chip. If the IMU bias is too sensitive to the impact of stress, it will also affect the zero drift estimation error, thus affecting the fusion effect.

5. Impact of impact on zero deviation

When the IMU is subjected to an external impact (on the order of tens of G), it is possible that the IMU will get stuck or the deviation will change. In general, testing should be done.

6. Nonlinear factor (%Fs)

Ideally, we consider the sensor data to be linear over this range. In fact, the sensor changes are non-linear. As shown in Figure 2, the nonlinear characteristics of the IMU need to be tested before use. If the nonlinearity is too severe, nonlinear calibration should be performed. There are many such calibration methods, such as proportional calibration, quadratic fitting calibration, etc.

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Application of Tilt Sensor in Monitoring of Sand Dredging Ship

 

Tilt sensor can measure the pitch angle and roll angle of fishing vessel in real time.

Sand dredgers, fishing vessels, that is, fishing vessels, can carry out class fishing, processing, transportation vessels collectively referred to. Fishing vessels are vessels that catch and harvest aquatic plants and animals, and also include some of the auxiliary vessels of modern fishing production, such as vessels that carry out aquatic product processing and transportation, aquaculture, resource surveys, fisheries guidance and training, and fisheries administration tasks.

Most fishing vessels are small, in order to adapt to continuous navigation and operation in the wind and waves, they require better stability, seakeeping and seaworthiness, and the structure needs to be particularly strong. During the operation of the fishing vessel, the load varies greatly and is small and medium.

Type II fishing vessels are generally tens to hundreds of tons; Large fishing vessels up to 1,000 tons, even up to more than 40,000 gross tons. In addition to the general Marine equipment, the fishing boat also needs to be equipped with fishing and navigation communication instruments such as winch, tilt sensor and navigator. In particular, the tilt sensor, which plays a very important role for the driver, is an instrument for measuring the tilt angle of the object in real time. The ER-TS-3160VO tilt sensor can measure the real-time pitch angle and roll angle of the fishing vessel in real time, and can be displayed through the corresponding display instrument, so that the driver can control the current operating attitude of the ship in real time, and adjust the running direction in time. Thus, it is easier for the stable operation of the ship, and it has gradually become one of the indispensable instruments most commonly used by the driver.
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Revealing the working principle and application scenarios of inertial navigation IMU

 Inertial navigation IMU is a very important navigation equipment, which can help aircraft, ships, automobiles and other vehicles achieve accurate navigation and positioning. Its working principle is based on inertial sensors, including accelerometers and gyroscopes, which calculate displacement and azimuth angle by measuring the acceleration and angular velocity of moving objects. This article will reveal the working principle and application scenarios of inertial navigation IMU.

Part 1: How Inertial Navigation IMU Works

The core of the inertial navigation IMU is the inertial sensor, in which the accelerometer can measure the acceleration value of the object, and the gyroscope can measure the angular velocity value of the object. The accelerometer can simultaneously measure the acceleration values of an object in three coordinate axes by installing sensors in different axes. A gyroscope measures the angular velocity of an object at three angles by measuring its rotational motion.

When an inertial navigation IMU is installed on a vehicle, it can calculate the vehicle's displacement and azimuth angle by measuring the acceleration and angular velocity of the vehicle's motion. Therefore, the inertial navigation IMU can achieve precise positioning and navigation without GPS signals.

Part 2: Application scenarios of inertial navigation IMU

Inertial navigation IMU has a wide range of application scenarios and is often used for navigation and positioning of vehicles such as aircraft, ships, cars, drones, robots and missiles. In the aviation field, inertial navigation IMU can realize motion control of aircraft such as climbing, descending, turning and taxiing, improving flight safety and accuracy. In the automotive field, inertial navigation IMU can help vehicles achieve autonomous driving and traffic jam identification, improving driving performance and safety.

Part 3: Development Trend of Inertial Navigation IMU

With the development and application of science and technology, inertial navigation IMU is also constantly developing and improving. In the future, inertial navigation IMUs will be more intelligent and agile, and can achieve more precise and complex navigation and positioning through technologies such as artificial intelligence and machine learning. In addition, with the popularity of consumer electronics and the Internet of Things, inertial navigation IMUs will also enter more daily life scenarios, such as health monitoring, smart homes and other fields.

Conclusion: Inertial navigation IMU is a very important navigation equipment, which can help vehicles achieve accurate navigation and positioning. This article introduces the working principle and application scenarios of inertial navigation IMU in detail, and discusses its future development trends. In the process of continuous innovation and improvement, inertial navigation IMU will continue to bring convenience and safety to human transportation, production and life.

ERICCO has developed tactical-level IMUs ER-MIMU03 and ER-MIMU07 and navigation-level IMUs ER-MIMU01 and ER-MIMU05, which can be widely used in many fields, such as UAV navigation, surveying and mapping, mining, etc. . If you want to know more about IMU products, please click the link below and get in touch with us, and we will have professionals explain it to you.

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Take you to know the accelerometer

 An accelerometer is an electronic sensor that measures the acceleration applied to an object to determine its position in space and monitor the object’s motion. Acceleration is a vector, which is the rate of change of the object’s velocity (velocity is the object’s displacement divided by the change in time). An accelerometer consists of a detecting mass (also known as a sensitive mass), a support, a potentiometer, a spring, a damper, and a housing.

Measuring range:

The level of acceleration supported by the sensor output signal specification is usually expressed in ±g. This is the maximum acceleration that the device can measure and accurately represent through the output. For example, the output of a ±3g accelerometer is linear with accelerations up to ±3g. If you accelerate to 4g, the output may be invalid. Note that the limit value is specified by the absolute maximum acceleration, not by the measurement range. 4g acceleration will not invalidate the ±3g accelerometer.for example, the ER-QA-03D Quartz Accelerometer for Oil and Gas has a measuring range of ±30g and a guaranteed bias repeatability of 50μg, which can achieve an operating temperature environment of -55 to 180 ° C in the oil and natural fields.

Accelerometer sensitivity:

The ratio of the acceleration (input) change to the change in the output signal. It defines the ideal linear relationship between acceleration and output (the gray line in Figure 1). Sensitivity is specified by a specific supply voltage, typically mV/g for analog output accelerometers and LSB/g or mg/LSB for digital accelerometers. It is usually expressed as a range (minimum, typical, maximum), or as a typical value plus a percentage deviation (%). For analog output sensors, the sensitivity is proportional to the supply voltage. For example, if the power supply is doubled, the sensitivity is doubled.

The change in sensitivity caused by temperature is generally expressed as a percentage (%) change per °C. The temperature effect is caused by the combination of mechanical stress and temperature coefficient of the circuit.

Nonlinearity:

Ideally, there is a linear relationship between voltage and acceleration, which is described by the sensitivity of the device. The degree of non-linearity measures the deviation between the actual sensitivity and the ideal constant sensitivity, expressed as a percentage relative to the full-scale range (%FSR) or positive-negative full-scale (%FS). Usually, FSR = FS+FS. The nonlinearity of ADI accelerometers is very low and can be ignored in most cases.

The working principle of accelerometer:

1. The sensor in an accelerometer is a sensor that is connected to gravity. There are two components that act on gravity: the accelerometer chip and the yoke. When the object accelerates or decelerates, the acceleration chip is subjected to the action of gravity force, thus converting the signal change into an electrical number; The yoke converts the change in the signal into a change in the magnetic field, and the changed magnetic field can be received by the sensor to generate data for the computer.

2. When the object is moving, the gravity sensor will detect the acceleration and deceleration of the object, the sensor will convert these signals into data through the circuit board, by the circuit board into a signal, and then through the interface to read the data and the computer connection, the computer can read the received signal.

Accelerometers are widely used in many fields. In the automotive industry, accelerometers can be used to measure the acceleration and braking force of a vehicle, thus providing information on the safety of the driver. In the field of aerospace, accelerometers can be used to measure the acceleration and attitude of aircraft, so as to ensure the stability and safety of aircraft. In addition, accelerometers can also be used for a variety of applications such as movement monitoring of athletes, screen rotation of smartphones and step count of smart watches.

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