Accelerometer

1 definition editing

English name:acceleration sensor
Definitions: Sensors that can sense acceleration and convert it into usable output signals Applications: Mechanical engineering (first-level disciplines); Sensors (two-level disciplines); Physical quantity sensors (three-level disciplines).

2 Category Edit Piezoelectric

Piezoelectric acceleration sensors are also called piezoelectric accelerometers. It is also an inertial sensor. The principle of the piezoelectric acceleration sensor is to use the piezoelectric effect of the piezoelectric ceramic or quartz crystal. When the accelerometer is subjected to vibration, the force applied by the mass to the piezoelectric element also changes. When the measured vibration frequency is much lower than the natural frequency of the accelerometer, the change in force is proportional to the measured acceleration.

Piezoresistive

Based on the world's leading MEMS silicon micromachining technology, piezoresistive acceleration sensors have features such as small size, low power consumption, and are easy to integrate in various analog and digital circuits. They are widely used in automotive crash tests, test instruments, equipment vibration monitoring, etc. field.

Capacitive

Capacitive acceleration sensors are capacitive sensors based on the capacitance principle. The capacitive acceleration sensor/capacitive accelerometer is a relatively common acceleration sensor. In some areas there is no substitute, such as airbags, mobile phones and other mobile devices. Capacitive acceleration sensors/capacitive accelerometers use a micro-electro-mechanical systems (MEMS) process that becomes economical in mass production, thus ensuring lower costs.

Servo type

The servo-type acceleration sensor is a closed-loop test system with features such as good dynamic performance, large dynamic range, and good linearity. Its working principle, the sensor's vibration system consists of "mk" system, and the same as the general accelerometer, but the mass m is followed by an electromagnetic coil, when the base has an acceleration input, the mass deviation from the equilibrium position, the size of the displacement by The displacement sensor is detected and converted into a current output after being amplified by the servo amplifier. The current flows through the electromagnetic coil and generates an electromagnetic restoring force in the magnetic field of the permanent magnet, so as to keep the mass in the original equilibrium position in the instrument housing. The servo acceleration sensor works in closed loop. Due to the feedback, the anti-jamming capability is enhanced, the measurement accuracy is improved, and the measurement range is expanded. The servo acceleration measurement technology is widely used in inertial navigation and inertial guidance systems, and also has application in high-precision vibration measurement and calibration.

3 application editing range

By measuring the acceleration due to gravity, you can calculate the tilt angle of the device relative to the horizontal plane. By analyzing dynamic acceleration, you can analyze how the device moves. But at the beginning, you will find that the inclination and acceleration of the light measurement do not seem to be very useful. However, engineers have come up with many ways to get more useful information.

Acceleration sensors help robots understand the environment in which it is located. Is it climbing? Still downhill, fell? Or for flying robots, it is also crucial to control the attitude. It is even more important to ensure that your robot does not carry bombs to go to crowds of people. A good programmer can use an accelerometer to answer all these questions. Acceleration sensors can even be used to analyze engine vibrations.

Acceleration sensors can measure the acceleration produced by traction.

Cases

Acceleration Sensor Applied to Seismometer Design

Seismic detector is a special sensor for geological exploration and engineering measurement. It is a sensor that converts ground vibration into electrical signals. It can convert ground vibrations caused by seismic waves into electrical signals and convert them into binary data through analog-to-digital converters. , conduct data organization, storage, and operation processing. The accelerometer is an electronic device that can measure acceleration force. Typical applications include mobile phones, laptops, pedometers, and motion detection.

Acceleration sensor technology applied to car accident alarm

In the modern era of rapid development of the automobile industry, automobiles have become one of the main means of transportation for people to travel, but the number of casualties caused by traffic accidents is also very large. The modern use of information technology to save people’s lives will be one of the major themes of research. The acceleration-based accident warning system is based on this design concept. It is believed that the promotion of this system will give the automotive industry a More safety.

Accelerometers are used to monitor high voltage wire galloping

At present, two major technical solutions, video image acquisition and motion acceleration measurement, are commonly used for wire glide monitoring. The former in the field of high temperature, high humidity, severe cold, dense fog, dust and other weather conditions, not only on the reliability of video equipment, stability and high requirements, but also the effect of the video images will be affected, in actual use It can only be used as an auxiliary monitoring method and cannot quantitatively analyze the movement parameters of the wire. Using the accelerometer to monitor the wire galloping condition can quantitatively analyze the up and down vibration and left and right oscillations at a certain point of the transmission wire, but only the amplitude of the linear motion of the wire can be measured. Frequency, and for complex circular motion, it cannot be measured accurately. So we must accelerate the development of accelerometers to adapt to applications such as these environments.

specific

Car safety

Acceleration sensors are mainly used for safety performance of automobile airbags, anti-lock braking systems, and traction control systems.

In safety applications, the rapid response of an accelerometer is very important. When the airbag should pop up, it must be determined quickly, so the accelerometer must react in an instant. By using a sensor design that can quickly reach steady state instead of vibration, the device response time can be shortened. Among them, piezoresistive acceleration sensors have developed fastest due to their wide application in the automotive industry.

Game control

The acceleration sensor can detect changes in the inclination of the up, down, left, and right sides. Therefore, it becomes simple to control the front, rear, left, and right directions of the objects in the game by tilting the hand-held device back and forth.

Automatic image flipping

The acceleration sensor detects the rotation and direction of the hand-held device to achieve the correctness of the image to be displayed.

Electronic compass tilt correction

Magnetic sensors determine the direction by measuring the amount of magnetic flux. When the magnetic sensor is tilted, the magnetic flux passing through the magnetic sensor will change, causing the direction to point to produce an error. Therefore, if the electronic compass without tilt correction requires the user to place it horizontally. The principle that the acceleration sensor can measure the inclination angle can compensate the inclination of the electronic compass.

GPS Navigation System Dead Angle Compensation

The GPS system determines the position of the object by receiving three satellite signals distributed in 120 degrees. In some special occasions and landscapes, such as ramps, high-rise buildings, and jungle areas, the GPS signal will become weak or even completely lost. This is the so-called dead-end. With the addition of an accelerometer and the inertial navigation we used before, we can measure the system dead zone. By integrating the acceleration sensor once, it becomes the amount of speed change in the unit time, and the movement of the object in the dead zone is measured.

Pedometer function

The accelerometer can detect the AC signal and the vibration of the object. When the person walks, it will produce a certain regular vibration, and the acceleration sensor can detect the zero-crossing point of the vibration to calculate the number of steps taken by the person walking or running. In order to calculate the displacement that people move. And using a certain formula can calculate the calorie consumption.

Anti-shake function

Use an acceleration sensor to detect the vibration/sway amplitude of the handheld device. When the vibration/sway amplitude is too large, the camera shutter is locked so that the captured image is always clear.

Flash message function

By waving handheld devices to display text in the air, users can write their own text. This flash letter function is to use the phenomenon of people's visual remnants, use the acceleration sensor to detect the period of the swing, and achieve accurate positioning of the displayed text.

Hard disk protection

The use of an acceleration sensor to detect the free-fall state provides the necessary protection to the mini hard drive. As we all know, when the hard disk is reading data, the distance between the head and the disk is very small. Therefore, the slight external vibration will have very bad consequences on the hard disk and cause data loss. The use of an accelerometer can detect the free-fall state. When a free-fall state is detected, the head is reset to reduce the damage of the hard disk.

Equipment or terminal posture detection

Acceleration sensors and gyroscopes are often referred to as inertial sensors and are often used in various devices or terminals to perform gesture detection, motion detection, etc., and are also suitable for people who play somatosensory games. The accelerometer uses the gravity acceleration and can be used to detect the tilt angle of the device, but it will be affected by the acceleration of the motion, so that the tilt angle measurement is not accurate enough, so it is usually necessary to use a gyroscope and a magnetic sensor for compensation. At the same time, when the magnetic sensor measures the azimuth angle, it also uses the geomagnetic field. When the current in the system changes or there is a magnetic material around, and when the equipment is tilted, the measured azimuth angle is not accurate. At this time, an acceleration sensor (inclinometer) is needed. And gyro compensation.

Smart products

The innovative function of the accelerometer sensor in the WeChat function has broken through the thousands of times of electronic products. This function realizes the characteristics of the sensor's direction, accelerometer, light, magnetic field, proximity, temperature and other parameters. This principle is an accelerometer integrated in the mobile phone. It can measure the acceleration values ​​of X, Y, and Z separately. The value of the X direction represents the horizontal movement of the mobile phone. The value of the Y direction represents the vertical movement of the mobile phone and the value of the Z direction. The size represents the vertical direction of the mobile phone, the direction of the sky is positive, and the direction of the earth is negative. Then the relevant acceleration value is transmitted to the operating system. By judging the size change, friends who are playing WeChat can be known at the same time.

4 main product editor

On April 4, 2014, the latest patent application issued by the U.S. Trademarks and Patent Office showed that Apple is developing a new type of earphone device. They try to add multiple sensors and microphones to the earphone to make the noise reduction function stronger. Make headphones smarter. [1]

This headset is wired and may be an improved version of the current EarPods. It is equipped with a variety of sensors, including acceleration sensors, and two microphones. When there is shaking, the acceleration sensor will be triggered to activate the noise reduction microphone on the headphone cable, forming a better noise reduction system than the current EarPods. However, this product is still only a patent status. For Apple, a company that is good at patent reserves, it may not be immediately used in new products. [1]

5 How it works

The principle of linear accelerometers is the principle of inertia, which is the balance of forces. A (acceleration) = F (inertial force) / M (mass) We only need to measure F. How to measure F? Use electromagnetic force to balance this force. It can be obtained that F corresponds to the current relationship. Just experiment to calibrate the scale factor. Of course, the middle of the signal transmission, amplification, filtering is the circuit thing.

Most accelerometers work on the principle of piezoelectric effect.

The so-called piezoelectric effect is "For the external force without a symmetric center, the external force added to the crystal, in addition to deforming the crystal, will change the polarization state of the crystal and establish an electric field inside the crystal. This is due to mechanical force. The phenomenon of polarization of the medium is called positive piezoelectric effect."

The general acceleration sensor utilizes its internal crystal deformation due to acceleration. Since this deformation generates a voltage, as long as the relationship between the generated voltage and the applied acceleration is calculated, the acceleration can be converted into a voltage output. Of course, there are many other ways to make acceleration sensors, such as piezoresistive technology, capacitance effect, thermal bubble effect, light effect, but the most basic principle is that the deformation caused by a certain medium is caused by acceleration, and the deformation is measured and used. The relevant circuit is converted into a voltage output. Each technology has its own opportunities and problems.

Piezoresistive acceleration sensors have developed fastest due to their wide application in the automotive industry. As security becomes more and more a selling point for automakers, there are more and more such additional systems. The market size of the piezoresistive acceleration sensor in 2000 was approximately 420 million U.S. dollars. According to relevant investigations, it is expected that its market value will increase at an average annual rate of 4.1%, reaching 560 million U.S. dollars by 2007. Of these, the European market is the fastest, because Europe is home to many airbag and automobile manufacturers.

Piezoelectric technology is mainly used in industry to prevent machine failures. The use of such sensors can detect potential machine failures to achieve self-protection and avoid accidental injury to workers. This sensor has the quest of users, especially those in the quality industry. Reproducibility, stability and innateness. However, in many new application areas, many users do not have the awareness of using such sensors. Vendors risking access to this yet-to-be-developed market will be in trouble due to end-users' problems and solutions due to the use of such sensors. There is little understanding of the method. If these problems can be solved, it will promote the rapid development of piezoelectric sensors. In 2002, the market value of piezoelectric sensors was 300 million U.S. dollars, and its annual growth rate is expected to reach 4.9%, reaching 420 million U.S. dollars by 2007.

The use of an acceleration sensor sometimes encounters a situation where the output signal is distorted when measured in a low-frequency environment. A variety of measurement methods are used to determine the cause of the failure for a moment. After analyzing and summarizing, the main causes of distortion in measurement results are: The system low frequency signal-to-noise ratio is poor, and the influence of the external environment on the measurement signal. Therefore, as long as there is a distortion of the low-frequency measurement signal of the accelerometer sensor, compare the above three points to see which factor is causing the problem to be solved in a targeted manner.

6 Technical Index Editing

1, the technical indicators of sensitivity: For an instrument, generally the higher the sensitivity, the better, because the more sensitive, the more rapid changes in the acceleration of the surrounding environment, the acceleration changes, very naturally, The change in the output voltage is also correspondingly larger, so that the measurement is easier and more convenient, and the measured data is also more accurate.

2. Technical indicators of bandwidth: Bandwidth refers to the effective frequency band that the sensor can measure. For example, a sensor with hundreds of HZ bandwidth can measure vibration; a sensor with 50 HZ bandwidth can effectively measure inclination. Now.

3, technical indicators in terms of range: Measuring the movement of different things need different ranges, according to the actual situation to measure.

Resolve the sensor on the phone

Acceleration sensors are electronic devices that can measure acceleration forces. Acceleration force is the force acting on an object during acceleration. It is like the gravity of the earth, that is, gravity. Acceleration force can be a constant, such as g, or it can be a variable. Therefore, its range is larger than that of a gravity sensor, but generally it refers to a gravity sensor when the cell phone is referred to as an acceleration sensor, so both can be considered as equivalent.

Direction sensor

A cell phone direction sensor is a component that is installed on a mobile phone to detect the state of the cell phone itself, rather than the function of a commonly understood compass.

The mobile phone direction detection function can detect that the mobile phone is in vertical, upside down, left horizontal, right horizontal, up and down states. The mobile phone with a direction detection function has more convenient and user-friendly features. For example, after the mobile phone is rotated, the screen image can be automatically rotated and the length-width ratio can be switched. The text or menu can also be rotated at the same time so that you can read conveniently; when listening to the MP3. Someone may say: This is the same with that gravity sensor?

The two are not the same. The orientation sensor or application angular velocity sensor is more appropriate. Generally, the orientation sensor on the mobile phone senses the azimuth angle, rotation angle, and inclination angle on the horizontal plane. This is an example if you might feel a little theory. There are directional sensors that can play city racing games. Only the gravity sensor can play, but the result is very tangled.

In order to obtain highly realistic test data, the user should fully understand the operating characteristics of the instrument used, how these characteristics affect each other, how the overall environment affects these characteristics, and how the accelerometer affects the measured motion.

Accelerometers are key measurement elements and are available in a variety of designs. Each design pattern is designed for certain specific purposes in order to obtain high fidelity measurement data.

Engineers should carefully analyze the measurement requirements and choose the most suitable accelerometer. Usually, the most appropriate choice is to compare the sensitivity, weight, and frequency response.

The main operating characteristics of the sensor are divided into effective response and spurious response.

Effective response

The response of the sensor caused by the input mechanical vibration or shock in the sensor sensitive axis direction. This response is the correct use of the sensor to make measurements and obtain reliable data.

● spurious response

The sensor's response caused by other physical factors that exist simultaneously when using a sensor to measure mechanical vibrations or shocks. This response is a measure of interference and is undesirable. (See National Standard GB/T 13823.1-93)

The effective responses are:

Sensitivity; Magnitude and frequency response and phase frequency response; Nonlinearity.

The spurious response mainly includes:

Temperature response; Transient temperature sensitivity; Transverse sensitivity; Rotary motion sensitivity; Base strain sensitivity; Magnetic sensitivity; Mounting torque sensitivity; (See National Standard GB/T 13823.1-93)

● Sensitivity: (Sensitivity)

The ratio of the specified output to the specified input.

Reference sensitivity: (Reference Sensitivity)

The sensor's sensitivity value at a given reference frequency and reference amplitude.

The higher the sensor sensitivity, the greater the signal-to-noise ratio of the measurement system and the system is less susceptible to electrostatic interference or electromagnetic fields. For a specific type of accelerometer design, the higher the sensitivity, the heavier the sensor and the lower the resonant frequency. So how much sensitivity is chosen is limited by its weight and frequency response.

In general, the sensitivity of the sensor includes both amplitude and phase information, which is a complex number that changes with frequency.

● Magnitude and frequency response and frequency response

When the input mechanical vibration value is unchanged, the amplitude of the output power of the sensor changes with the vibration frequency, which is called the amplitude-frequency response. The phase of the output power varies with the vibration frequency and is called the phase-frequency response.

By continuously changing the vibration frequency within the working frequency band and keeping the input mechanical vibration amplitude unchanged, the output of the sensor can be observed and the amplitude-frequency response can be measured. If the phase difference between the output power of the sensor and the input mechanical vibration is measured at the same time, the phase-frequency response can be measured again.

In general, only the amplitude-frequency response is required to be known. Sensors are used at the lower and upper frequencies of the proximity sensor, or when required, the phase-frequency response must be known.

● Non-linearity

Within a given frequency and amplitude range, the output is proportional to the input, known as a linear change. The degree to which the actual sensor's calibration result deviates from the linear change is called the non-linearity of the sensor.

In the dynamic range of the sensor from the minimum value to the maximum value, the input mechanical vibration is gradually increased, and the sensor output amplitude is measured at the same time, and the deviation between the output value of the sensor and the linear output value can be determined. When using a sinusoidal vibration generator for measurement, several frequencies can be selected within the operating frequency range of the sensor to cover the entire dynamic range of the sensor.

Generally, the maximum deviation of the output value of the sensor from the linear value is near the upper limit of the dynamic range of the sensor. The amount of deviation allowed depends on the specific measurement requirements.

Piezo accelerometers are generally used within a certain range of acceleration, and the percentage of sensitivity increase represents non-linearity. Piezoresistive, variable capacitance accelerometers have good linearity in their dynamic range, which represents the combined value of nonlinearity, hysteresis, and non-repeatability.

● Influence of quality load

If the accelerometer's dynamic mass is close to the dynamic mass of the measured structure, it will cause a significant attenuation of the vibration. For this purpose, when measuring vibrations on thin, light sheet-like components such as printed circuit boards, lightweight accelerometers must be used to obtain accurate data. If the measured object exhibits a single degree of freedom response, the accelerometer will decrease its resonant frequency. Miniature accelerometers must be used in all modal tests.

● Low frequency response

Using piezoelectric accelerometers, the low frequency cutoff frequencies of the amplifiers used are typically 2-5 Hz, in order to eliminate the pyroelectric output of many piezoelectric sensors. Isolated designs, such as isolated shear designs, can be used at lower frequencies. Piezoresistive and variable capacitance accelerometers have zero frequency response.

● High frequency response

The high frequency response of an accelerometer varies with the accelerometer's mechanical properties and installation methods. When mounted securely, most accelerometers exhibit the frequency response of an undamped, single-degree-of-freedom system. With a requirement of ±5%, the frequency response is approximately flattened to one-fifth of the installed resonant frequency. If appropriate correction factors are added, useful data can be obtained at higher frequencies.

● Temperature response

The change in sensor sensitivity with temperature is called the temperature response of the sensor. The difference between the sensitivity at the test temperature and the sensitivity at room temperature is expressed as a percentage of the room temperature sensitivity.

The temperature range of commonly used piezoelectric accelerometers is below zero degrees to +177°C or +260°C. Some specific models, the absolute temperature of zero, up to 760 °C high temperature. A wide variety of piezoelectric accelerometer designs have a very flat temperature response over a wide temperature range. Piezoresistive, variable capacitance accelerometers typically have a temperature range of -18°C to +93°C.

Transient temperature sensitivity of piezoelectric sensors

A sensor with a pyroelectric effect will produce an electrical output under transient temperature. The ratio of the maximum value of this output to the product of the sensitivity of the sensor and the temperature change is called the transient temperature sensitivity.

When the temperature changes, the piezoelectric element generates an output signal, which is called pyroelectric effect. A sudden change in the temperature of the test piece or gas flow causes this temperature change. In most cases this effect is very low frequency and only the response of the signal conditioning instrument is below 1 Hz to detect it. If the signal conditioner has an interstage high-pass filter, special attention should be paid to the fact that the pyroelectric signal may saturate the amplifier and make it inactive for a short period of time.

Pedestal-isolated, shear-type, isolated shear-type designs have a smaller pyroelectric effect. Piezoresistive, variable capacitance type of this effect is negligible.

● Lateral sensitivity

For unidirectional measurements, it is necessary that the accelerometer must not produce any response to the lateral movement of the measured object. However, an accelerometer cannot be perfect. It always has a certain lateral sensitivity. It is related to the direction of lateral vibration. Its lateral sensitivity is generally 1 to 5% of the axial sensitivity. Enderflex calibrates the lateral sensitivity of each accelerometer and gives its maximum value.

Horizontal sensitivity ratio

The sensitivity of the sensor when excited in a direction perpendicular to the sensitive axis of the sensor is called lateral sensitivity. The ratio of lateral sensitivity to sensitivity in the direction of the sensitive axis is called the lateral sensitivity ratio.

● Rotary motion sensitivity

Some linear vibration sensors are sensitive to rotational motion. Care must be taken when conducting the test. In order to avoid measurement errors.

●Base strain sensitivity

When the sensor base is strained, it will cause undesired signal output. The ratio of the output value to the product of the sensor sensitivity and strain value is called the base strain sensitivity.

In some tests, there may be dynamic bending, twisting, stretching, etc., at the accelerometer mount. The accelerometer base also strains due to close contact with the strain zone. Part of the strain is transmitted to the sensitive element, which produces an output signal that is independent of the vibrational motion.

The shear design of the accelerometer is one order of magnitude less sensitive than the compression of the strain on the pedestal. Use insulated mounting screws or adhesive adapters to reduce this effect.

●Magnetic sensitivity

Sensors are placed in the magnetic field will produce an unwanted signal output, the output value and the sensitivity of the sensor and magnetic field magnetic induction product ratio, known as the sensor's magnetic sensitivity.

● Mounting torque sensitivity

With threaded sensors, changes in installation torque can cause changes in sensitivity. The ratio of the maximum difference between the sensitivity when the specified installation torque is 1/2 times the specified installation torque or the specified installation torque is applied to the specified installation torque and the percentage of the ratio when the specified installation torque is applied is called the installation torque sensitivity.

Special environment response

In the special environment of strong electrostatic field, alternating magnetic field, radio frequency field, sound field, cable influence, nuclear radiation, etc., some sensors will be seriously affected, these physical factors will cause the sensor to produce spurious response.

7 Selection Guide Edit Output Type

This is the first thing to consider. This depends on the interface between your system and the accelerometer. The voltage and acceleration of a typical analog output are proportional. For example, 2.5V corresponds to 0g acceleration, and 2.6V corresponds to 0.5g acceleration. Digital outputs typically use pulse width modulation (PWM) signals.

If you use a microcontroller with only a digital input, such as the BASIC Stamp, then you can only select the digital output acceleration sensor, but the problem is that you have to use an additional clock unit to process the PWM signal, and the processor is also A big burden.

If you use a microcontroller with analog inputs, such as PIC/AVR/OOPIC, you can simply use the analog interface acceleration sensor. All you need is to add a command like "acceleration=read_adc()" to your program. , and the speed of processing this instruction is only a few microseconds.

Measuring axis number

For most projects, two-axis accelerometers have already met most applications. For some special applications, such as UAV, ROV control, three-axis accelerometers may be suitable.

Maximum measurement

If you only measure the inclination of the robot with respect to the ground, a ±1.5g acceleration sensor is sufficient. But if you need to measure the dynamic performance of the robot, ±2g should be sufficient. If your robot has something like a sudden start or stop, you need a ±5g sensor.

Sensitivity

In general, the more sensitive the better. More sensitive sensors are more sensitive to changes in acceleration within a certain range, and the greater the change in the output voltage, the easier it is to measure, resulting in more accurate measurements. The minimum acceleration measurement is also called the minimum resolution. Considering the noise problem of the amplifier circuit at the rear stage, it should be kept away from the minimum available value to ensure the best signal-to-noise ratio. The maximum measurement limit should take into account the non-linear effects of the accelerometer itself and the maximum output voltage of the subsequent instrument. Estimation method: maximum measured acceleration x sensor's charge/voltage sensitivity, whether the above value exceeds the maximum input charge/voltage value of the associated instrument. If the known acceleration range can be selected in the “reference range range” of the sensor index (taking into consideration the frequency response and weight), at the same time, the sensitivity can be considered higher in the case of frequency response and weight allowable to improve the follow-up instrument. Input signal, improve signal to noise ratio.

8 Bandwidth Editing

The bandwidth here actually refers to the refresh rate. This means that the sensor will generate a number of readings per second. For applications where tilt is usually measured, the bandwidth of 50 Hz should be sufficient, but for dynamic performance, such as vibration, you will need a sensor with hundreds of HZ bandwidth.

Resistance/Caching Mechanism

For some microcontrollers to perform A/D conversion, the connected sensor resistance must be less than 10kΩ. For example, the acceleration sensor has a resistance of 32kΩ, which cannot work properly on PIC and AVR control boards. Therefore, it is recommended to carefully read the controller manual before purchasing the sensor to ensure that the sensor can work normally.

Cumulative error

The accelerometer measures the acceleration over a period of time, and then calculates the total displacement and end-point speed over the previous period based on the previously accumulated speed (including speed and direction) and position. The result can be obtained by repeated calculation.

Obviously, the sampling time will be shortened and the accuracy will be improved. But this will be subject to some technical restrictions, such as computer computing speed can not keep up; acceleration sensor itself has response time and so on. In addition, since the speed and the position are always accumulated, there is accumulated error, and for a long time, the total accuracy is greatly reduced.

9 Installation Notes Edit

The natural frequency of the accelerometer is determined by the degree of coupling, and choosing the right adhesive will be an important step. Some important issues that must be considered are: the weight of the accelerometer, the frequency and bandwidth of the test, the amplitude and temperature of the test. Also consider some of the problems that arise during the test: the limitation of the sine curve and the random vibrations that occur in the test. In general, engineers and technicians will choose suitable adhesives to bond the accelerometers according to the different needs of testing.
Acrylic sensors used for bonding adhesives generally include cyanoacrylates, magnets, double-sided adhesive tapes, paraffin waxes, and thermal adhesives. The key issue is how to effectively use these adhesives. In the bonding process of the acceleration sensor, the amount of adhesive used plays a key role in whether the acceleration sensor can achieve a good frequency response. Sticking the accelerometer with as little adhesive as possible on a small film will make the accelerometer's frequency response the best. Before installing the sensor, it is necessary to use carbonic acid solution to clean the surface to be installed. When installing the sensor, it is usually necessary to use cyanoacrylate, magnets, double-sided tape, paraffin wax, and evenly apply it on the adhesive accelerometer. The surface to be adhered should not be too thick or too thin. A suitable thickness will provide good adhesion. The use of hot adhesives has a lot of attention, and the most important thing is to pay attention to the setting time of hot adhesives during installation.
Of course, we need to pay attention when using the adhesive installation is close to the maximum limit temperature is best not to use adhesive, it should be delayed for a while before use, otherwise it will cause the adhesive itself is damaged, resulting in lower tensile strength of the adhesive . In any case, all limit factors must be taken into account when we want to install acceleration sensors using adhesive bonding. Similarly, the above acceleration sensor installation is only for most situations, the measurement of acceleration on some special equipment needs to use the most suitable sensor installation.

10 Forecast Forecast Edit

According to the sensor market report of the consulting company INTECHNOCONSULTING, the global sensor market capacity in 2008 was 50.6 billion U.S. dollars, and the global sensor market in 2010 is expected to reach more than 60 billion U.S. dollars. The survey shows that Eastern Europe, Asia Pacific, and Canada have become the fastest growing areas for the sensor market, while the United States, Germany, and Japan are still the most widely distributed areas for the sensor market. Worldwide, the fastest-growing sensor market is still the automotive market, the second is the process control market, optimistic about the communications market.

Some sensor markets such as pressure sensors, temperature sensors, flow sensors, and level sensors have demonstrated the features of a mature market. Flow sensors, pressure sensors, and temperature sensors are the largest in the market, accounting for 21%, 19%, and 14% of the entire sensor market. The major growth in the sensor market comes from emerging sensors such as wireless sensors, MEMS (Micro-Electro-Mechanical Systems) sensors, and biosensors. Among them, the wireless sensor's compound annual growth rate in 2007-2010 is expected to exceed 25%.

The global sensor market is showing rapid growth among the ever-changing innovations. Relevant experts pointed out that the major technologies in the field of sensors will be extended and improved on an existing basis. Countries will compete to accelerate the development and industrialization of new generation sensors, and competition will become increasingly fierce. The development of new technologies will redefine the future market of sensors, such as the emergence and market share of new sensors such as wireless sensors, fiber optic sensors, smart sensors and metal oxide sensors.

Capacitance sensors are expected to have a strong growth, and growth will be faster after 2004. It is estimated that the comprehensive annual growth rate from 1997 to 2007 will be 5.9%, of which the highest may reach 33.2%. Its market value will be $0.75 billion in 2000. In 2007, it will reach 110 million U.S. dollars. Automotive and industrial users from Europe and North America are the main buyers of these products. In 2000, North America accounted for 40.4% of the market, and Europe accounted for 48.9%. The automotive industry uses capacitive sensors for safety systems, tire wear monitoring, inertial brake lights, headlamp leveling, seat belt retraction, automatic door locks, and airbags. Capacitive sensors are very attractive to designers because they do not need to touch the test object, so they do not have to be squeezed into a narrow space.

11 Latest Development Editor

With the proliferation of smart phones and other devices, higher functionality and designability are required. In this case, there is a strong demand for highly integrated and miniaturized components. In addition, higher performance leads to increased battery consumption. Therefore, lower power consumption is required for various components mounted on the device. The industry's smallest size accelerometer has a maximum resolution of 14bit, low power consumption, high shock resistance and programmable standby wake-up function, enabling tilt detection, motion detection, etc.; while another high performance, low power consumption, low Cost, low noise acceleration sensor with high stability, the highest resolution up to 4bit features, high-precision tilt detection, motion detection, these two devices are mainly used in smart phones, tablet / laptop computers, digital cameras, game consoles And other small people's livelihood equipment.

The demand for devices with more sensory movements, such as smart phones and game consoles, has increased. In addition, new demands have emerged for smart televisions such as sports remote control. In these motion detections, historically used accelerometers were used, gyroscopes were also added, and operational sensations were improved. The small package gyroscope uses a FIFO buffer to reduce the frequency of access from the microcontroller and has a rotary motion detection function. With the acceleration of acceleration sensors and gyroscopes, there are increasing cases of use in small devices. There is an increasing demand for using two sensors together with one chip and one communication interface in one system.小型封装的3轴加速度传感器和3轴陀螺仪的复合传感器的渐渐出现，不但具有以上小型封装陀螺仪的各种特点和功能，同时还拥有业界领先的低耗电量，仅为4mA。他们多应用于智能手机、平板电脑、游戏机、遥控器、PND及其他小型民生设备。