Recently, Twimbit, a Singapore-based product research and consulting company, released a research report that predicts and analyzes the 15 largest sensors in the global market from 2020 to 2023, which are selected from hundreds of major sensor categories. These 15 sensors together accounted for 79.88% of the total global share in 2020, as shown in the figure below:

Among the 15 largest sensors in the market, pressure sensors ranked sixth, with a global market size of $9.169 billion in 2020 and is expected to increase to $11 billion in sales by 2023, at a CAGR of 6.3%. Pressure sensors are extremely versatile and have multiple application scenarios, such as industrial Internet, consumer electronics, automotive, biomedical, aerospace, natural gas, chemical, mining, power, building automation, HVAC, food processing, pharmaceutical, healthcare, environmental monitoring, and many more.

So, in the face of a wide variety of pressure sensors, many models, how should we choose a suitable sensor? This involves the selection principle of the sensor, that is, to choose the most suitable price to meet its use, pressure range, accuracy requirements, temperature range, electrical requirements, operation mode, pressure sealing requirements and other indicators of the pressure sensor, when the pressure sensor is installed on the equipment, to run normally and stably, accurate measurement, durable. We will divide into two sections to cover the important aspects that must be considered in the selection of pressure sensors.

The pressure sensor is divided into traditional pressure sensor and MEMS pressure sensor, in practical application, MEMS pressure sensor gradually replaces the traditional pressure sensor with its advantages of small size, high precision and good stability. Therefore, this article mainly focuses on MEMS pressure sensors.

Considerations for uses

Due to the different structures, pressure sensors can be divided into absolute pressure sensors that measure absolute pressure, gauge pressure sensors that measure the relative pressure to the atmosphere, and differential pressure sensors that measure the pressure difference between the two places.

When determining absolute pressure (i.e., absolute pressure sensor), the sensor itself has a vacuum reference pressure, and the measured pressure is independent of atmospheric pressure, but relative to the vacuum.

The relative pressure to the atmosphere is based on the atmospheric pressure, so the elastomeric membrane side of the sensor is always connected to the atmosphere. Since atmospheric pressure is related to the height above the ground, changes in the amount of water vapor in the atmosphere during the four seasons, and changes in the content of the various gases that make up the atmosphere at different locations. Therefore, the measured relative pressure is related to the above factors.

In addition, fluid pressure can be introduced separately from both sides of the sensor's elastomeric membrane, so that the differential pressure between different parts of the fluid or between fluids can be determined.

Therefore, pressure sensors with different structures should be selected for different applications.

Pressure range considerations

The pressure range of the pressure sensor is graded because the elastic membrane of the pressure sensor has a limit to the fluid pressure. This is commonly referred to as the pressure limit, beyond which the elastic membrane will break. Sensors all have different overvoltage capacities, generally speaking, each sensor has 20%~300% overvoltage capability.

The selection of pressure range should mainly consider three factors: the maximum overpressure capacity of the sensor, the relationship between accuracy and pressure range, and the relationship between the price of the sensor and the pressure range.

1. When considering the maximum overvoltage capacity, special attention should be paid to the difference between static pressure and dynamic pressure. Because, the dynamic pressure often appears impact pressure, and even shock waves, and the impact pressure is much higher than the static pressure, if the maximum working pressure range is selected refers to the static pressure, the sensor should be selected when bearing the dynamic pressure, should choose a larger overpressure capacity, otherwise the impact pressure is easy to reach the limit of the pressure, so that the pressure sensor is damaged.

2. We should also pay attention to the relationship between accuracy and range, in general, there are differences in the accuracy of pressure sensors of different ranges, and it is easier to meet the accuracy requirements when selecting the appropriate range.

3. For the relationship between price and range, generally speaking, the price of pressure sensors of 0.3~1MPa is cheaper, and the price of pressure sensors below 0.1MPa or more than 1MPa is more expensive.

Consideration of accuracy requirements

Accuracy is a term commonly used in the sensor industry to describe the output error of a sensor. It is derived from nonlinearity, hysteresis, non-repeatability, temperature, zero equilibrium, correction and humidity effects. Typically, we specify accuracy as a combination of nonlinearity, hysteresis, and non-repeatability.

Static accuracy refers to the accuracy that should be achieved at a specific temperature (room temperature 25°C). It can be divided into four grades: 0.01~0.1%FS for ultra-high precision, 0.1~1%FS for high precision, 1~2%FS for ordinary accuracy, 2~10%FS for low precision. Full temperature range accuracy refers to the accuracy that a pressure sensor should achieve over the entire operating temperature range, and can also be divided into four levels with the same static accuracy.

The thermal zero drift and thermal sensitivity drift coefficient and nonlinear error of the pressure sensor are important indicators affecting the accuracy of the sensor. For the same pressure sensor, the thermal zero drift coefficient decreases with the increase of working pressure, while the thermal sensitivity coefficient and nonlinear error increase with the increase of working pressure.

In general, sensors with higher accuracy will cost more, but when a pressure sensor achieves high accuracy, it is necessary to add a lot of additional processes to the manufacturing process, as well as calibration processes and compensation technologies. Therefore, reasonable accuracy requirements should be put forward according to the actual application and requirements of the pressure sensor.

There are also considerations for the selection of pressure sensors, such as electrical requirements, operating methods (media), operating temperature ranges, and pressure sealing requirements, which we will focus on in the next article.

Beijing Zhixin Sensing Technology Co., Ltd. independently develops and produces a variety of MEMS pressure sensors, which cover a variety of structures such as absolute pressure, gauge pressure, differential pressure, etc., and in terms of pressure range, it includes a variety of range ranges, such as 300~1200hPa, 10~115KPa, 50~400KPa, 0~4MPa, and realizes that the range can be customized. The second-order temperature drift calibration of sensitivity and the highest third-order nonlinear calibration of sensitivity, the highest calibration accuracy can reach 0.1%, and the full scale accuracy of most types of pressure sensors can be guaranteed to be within ±1%FS, which is at the leading level among similar products in China.