“Sensors are the first point of contact for accurate and valid data; they play an important role in the process of converting raw physical quantities into data quantities that are easy to measure and calculate. With the rapid development of various engineering technologies such as electric power, shipbuilding, aviation, and aerospace, more and more accurate dynamic data is required for related application scenarios. Aero-engines, gas turbines, steam engines and other high-energy power devices have put forward more stringent requirements for industrial-grade sensors.

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Sensors are the first point of contact for accurate and valid data; they play an important role in the process of converting raw physical quantities into data quantities that are easy to measure and calculate. With the rapid development of various engineering technologies such as electric power, shipbuilding, aviation, and aerospace, more and more accurate dynamic data is required for related application scenarios. Aero-engines, gas turbines, steam engines and other high-energy power devices have put forward more stringent requirements for industrial-grade sensors. Among the many sensors, the author takes industrial-grade accelerometers as an example, combines application and related product data, and briefly shares some experiences and experiences.

What is an accelerometer?

Accelerometer, also known as accelerometer, accelerometer, is a sensing device used to measure acceleration. The device measures the inertial force on itself during the acceleration process, and obtains the acceleration value through Newton’s second law. From the induction mechanism, it is divided into piezoelectric type, capacitive type, inductive type, strain type, piezoresistive type and so on.

Vehicle Ride Test Application

The acceleration sensor is installed on the vehicle seat, and the vibration acceleration process in the three axes of XYZ is measured, which is used to evaluate the road test of the ride comfort of the vehicle.

Industrial grade accelerometer

When choosing an acceleration sensor, users are mostly based on the acceleration range and combined with practical applications. Such as tilt angle measurement, a range of ±1.5g is sufficient. Accelerometers of ±2g can be used in most consumer electronics and commercial applications. However, for measurement applications with emergency stop, violent changes in multiple directions, and high vibration intensity, at least an accelerometer with a range of ±10g or more should be selected.

In many industrial application scenarios, shock and vibration need to be monitored and measured. Due to the large fluctuation range of high and low temperature in the application environment, the range, sensitivity and accuracy of the accelerometer are required to be high. For conventional acceleration sensors, it is completely impossible. Competent for this harsh and harsh working environment. Based on this industrial-grade accelerometer, they are fully capable of maintaining high-reliability continuous measurement and stable output in this harsh application environment.

Brands and product performance of industrial-grade accelerometers

In the sensor market, there are many brands of industrial-grade accelerometers, among which European, American and Japanese brands occupy a large proportion of the market share of such products. However, with the rapid development of engineering technology in China in recent years, China’s own brands are also gradually catching up in this segmented product field, and are competing with Europe, the United States and Japan in high, medium and low technical dimensions. . From the perspective of product technology and reliability, the industrial-grade accelerometers of the imported brand American PCB, Danish B&K and China’s own brand FATRI can comprehensively interpret these two dimensions.

PCB Piezotronics, Inc. “PCB” is an acronym for PicoCoulomB, a technical term that defines the type of charge produced by a piezoelectric sensor fabricated from a PCB, and is also a registered trademark of the company. Founded in 1967, PCB is an established family business in the United States. Has acceleration measurement, vibration, shock, acoustics, load and other product lines.

Brüel & Kjær is referred to as B&K. The name and trademark are derived from the names of the founders Per Vilhelm Brüel and Viggo Kjær, who originated from Copenhagen Institute of Technology (now the Technical University of Denmark), a company with a long history, founded in 1942, with acceleration measurement, Microphone, acoustic holographic array and other product lines.

FATRI (Xiamen) Technology Co., Ltd. – FATRI, founder Dr. Nie Yongzhong, this is a long-lasting Chinese independent brand, “long” is that its founder Dr. Nie has been deeply involved in the research and development and design of precision advanced sensors, ” New” because the company has only been around for over 5 years. Although it has been established for a short time, it has rich and solid product development and manufacturing capabilities such as advanced materials, chip manufacturing, precision sensors (acceleration, temperature, pressure, etc.), measurement equipment, etc.

The author selects similar products of industrial-grade accelerometers from three brands of products, and analyzes some characteristics and key technical indicators of industrial-grade sensors through product technical specifications.

Key technical indicators of industrial-grade accelerometers

Sensitivity

The larger the voltage sensitivity is, the better it is on the premise of satisfying the resonant frequency, and the easier the back-end sampling and conditioning loop is.

Operating temperature

In the industrial field environment, the temperature will suddenly rise and fall at any time. Whether the measurement can be carried out effectively will directly affect the efficiency of the measurement. Therefore, the working temperature range should be as wide as possible.

Response time

When the measured object changes, the sensor cannot respond immediately, and there is a general lag. The length of the lag is the response time, and the shorter the response time, the better.

impact limit

Refers to the maximum acceleration shock that the sensor and the housing can withstand within 1 second. Generally, within the range that can withstand the shock, the sensor can still maintain normal operation. The higher the upper limit of the shock limit, the better.

Lateral sensitivity

When measuring a certain direction, the signal output should theoretically be all the sensing direction, but in fact, there will be signal output in the vertical direction of the direction, which is caused by the lateral effect, so the lower the lateral sensitivity, the better the performance. The national standard requirement is less than or equal to 5%.

Nonlinearity

In the fixed frequency and amplitude range, when the output is proportional to the input, it becomes a linear change. The degree to which the calibration result of the actual sensor deviates from linearity is called the nonlinearity of the sensor. The smaller the indicator, the better.

Frequency response

Generally, the upper limit of the operating frequency of an accelerometer is about 1/3 of its own resonant frequency. Usually, the accelerometer has poor low-frequency characteristics and serious signal attenuation. However, in the high-frequency band, the linearity is poor, and the nonlinear effect is large. In practical applications, the frequency range of civil engineering structures is about 0.2~1kHz, and most of general mechanical equipment belongs to the mid-frequency range, with a frequency range of about 0.5~5kHz. High-energy power devices range from low frequency to high frequency, and the frequency range will be greater than 5kHz. In addition, the rigidity of the sensor installation also has a certain influence on the frequency range measured by the sensor. The frequency response range of an industrial-grade accelerometer directly affects its measurement efficiency in different application scenarios.

From the above indicators, we can see that the range of industrial-grade accelerometers is wider than that of non-industrial-grade sensors, and the working temperature range can withstand a wide range of high and low temperature cyclic conversions, and can guarantee under such conditions. Relatively good sensitivity, and the lateral sensitivity can be controlled in the smallest possible range, and at the same time can withstand the impact of thousands of g. The collection of these elements is equivalent to putting forward extremely high requirements for the R&D, design and production of sensors. In the actual manufacturing process, every tiny process error will have a huge impact on the sensor itself.

As an internationally renowned professional manufacturer of sensors, PCB and B&K have strict and strict requirements on product technical specifications, and have a good reputation in practical applications. It is worth mentioning that, as a Chinese independent sensor brand, FATRI can achieve such a high level of products in such a short period of time. It has to be said that it is an enterprise with strong technical strength. After all, in the sensor manufacturing industry, in engineering technology, technical strength and R&D and design capabilities are the primary productive forces.

The author has learned from many sources that FATRI is a hard-core technology company with all-round capabilities in materials, sensor chip design and manufacturing, packaging, testing, and precision sensor manufacturing. In just 5 years, this company has pioneered more than 600 international patent designs such as the base wedge-shaped self-locking shear structure. In an industry with heavy assets, high technical threshold and long R&D cycle, such as advanced sensor manufacturing, it is even more valuable to make such a competitive industrial-grade sensor in the current impetuous and speculative environment. As a member of the industry, I can imagine how many hardships and tribulations I have to go through in this process. But this kind of dedication and perseverance is worth it. We need more such technological innovation enterprises that can endure loneliness and possess the spirit of craftsmanship.

At present, under the trend of rapid development of various engineering technologies and cutting-edge technologies, in the field of industrial sensors, European, American and Japanese products are still very competitive. However, with the development of global market demand, it is believed that in the future, more Chinese sensor independent brands will go to the world and compete with international manufacturers on the same stage. The turbulent international situation has always affected the changes in the market structure. As a latecomer, you need to uphold the original intention and unswervingly follow the correct route of independent R&D and manufacturing. The author hopes that more Chinese sensor independent brand manufacturers with core technical strength like FATRI can compete with foreign sensor companies such as Europe, the United States, and Japan in more application fields.

In this era of coexistence of opportunities and challenges, only hard work can take a place. Elon Musk said in his autobiography: “The so-called entrepreneurship is to chew on glass and stare into the abyss. Since you have to go through hell, go on. “.

knowledge sharing

1. Piezoelectric effect: After the piezoelectric crystal is deformed by force, polarization will occur inside it, and at the same time, charges of opposite signs will be generated on its two surfaces. When the measured vibration frequency is much lower than the natural frequency of the accelerometer (resonance). frequency), the force change is proportional to the measured acceleration. When the external force is removed, it returns to an uncharged state, a phenomenon called “piezoelectric effect”.

2. When measuring the structure to be tested in the working state, it is best to use the sensor with “isolation”. If the sensor itself does not have isolation, insulating material can be added to the bottom of the sensor to act as an isolation device.

3. The operating frequency range of the applied sensor is slightly higher than the actual measured bandwidth.

4. The axial direction is very important, single-axis accelerometers are usually used to measure simple vibration and acceleration conditions; dual-axis accelerometers refer to measuring acceleration and vibration along the X and Y axes (front, rear & left, right); three Axis accelerometers add the Z-axis to a dual-axis accelerometer for complex three-dimensional positioning and measurement.

5. The accelerometer is also limited by the vibration frequency range and must match the frequency of the intended application.