A differential pressure sensor (DPS) is a sensor used to measure the difference between two pressures. It is a differential pressure measuring element that uses a stainless steel corrugated diaphragm for isolation. Its working principle involves using isolation diaphragms to protect both the high and low pressure ends. Both pressure chambers can contact a fluid medium with a certain degree of corrosiveness. The measured differential pressure is transmitted to the silicon pressure-sensitive element through the isolation diaphragm and the filled silicone oil, achieving accurate measurement of the differential pressure. The differential pressure transmitter utilizes the piezoresistive effect of the conductor silicon material in the differential pressure sensor to convert the differential pressure into an electrical signal. Because the signal output from the Wheatstone bridge on the sensitive chip has a good linear relationship with the differential pressure, accurate measurement of the measured differential pressure can be achieved. Differential pressure transmitters are widely used in industrial process control, flow measurement, medical instruments, aerodynamic measurement, hydraulic and pneumatic equipment, and other fields.
The working principle of a differential pressure sensor is based on a simple and effective principle: the change in force caused by a pressure difference. Typically, a differential pressure sensor consists of two sensing elements separated by a fluid or gas filling the space between them. When the fluid or gas passes through the sensor, a pressure difference is generated due to changes in fluid velocity or pipe geometry, which in turn causes a change in force within the sensor. This change in force can be measured by the deformation of the sensing element or changes in physical quantities such as resistance, capacitance, and inductance.
With increasing attention being paid to the automotive industry, automakers believe that increasing the number of electronic devices in vehicles and promoting automotive electrification are crucial and effective means to capture the future automotive market. Consequently, fuel economy requirements and emission standards are becoming more stringent, leading to the application of more and more systems in automobiles, such as intake/exhaust management systems, fuel vapor management systems, brake assist systems, and diesel particulate filters. These systems all require pressure sensors to quickly and accurately obtain pressure information to determine the system's status and next steps.
Differential pressure sensors are primarily used to measure the pressure difference between the exhaust gas and the passages before and after the exhaust particulate filter (DPF) in automotive engines. To meet emission standards, a common method is to place a filter in the exhaust system to capture tiny particles in the exhaust gas. A drawback of this method is that the exhaust passages gradually become clogged as captured particles accumulate. To remove these accumulated particles, additional fuel is injected into the exhaust gas at a certain point in the passage or directly to raise the exhaust gas temperature. When a catalyst is present in the filter, the high temperature of the exhaust gas is sufficient to burn and vaporize the accumulated particles. This cleaning process is called "regeneration." A problem arises: too frequent regeneration increases fuel consumption; too long intervals reduce engine performance. The differential pressure sensor sends the pressure difference signal to the ECU, which uses this pressure difference to determine the degree of particle accumulation in the filter and decides the timing of "regeneration" and the amount of additional fuel injected. Simultaneously, the ECU can also regulate the exhaust gas temperature by controlling the EGR valve. A differential pressure sensor detects the pressure difference between the air inlet and outlet of the filter. When the pressure difference exceeds a set threshold, the filter is considered to be saturated. The ECU controls the engine temperature to increase, and the engine emits high-temperature exhaust gas to burn the particles stored in the filter, thus completing the filter regeneration.
A differential pressure sensor, as the name suggests, is a type of sensor, but it's used to transmit pressure differences, hence the name. Generally, its main function is to measure the difference between two different pressures and display the result. Differential pressure sensors are frequently used to measure the pressure difference between the two ends of a component in a piece of equipment.
Given the significant challenges faced in exhaust gas applications, stringent requirements are placed on differential pressure sensors. Sensata Technologies' differential pressure sensors possess the following characteristics:
First, superior drainage and anti-icing performance. Since condensation occurs in exhaust gas applications, the pressure chamber design needs to be optimized to achieve gravity-driven self-drainage. Furthermore, the water film on the inner wall of the sensor can automatically rupture due to pressure fluctuations in the piping system. This prevents sensor output errors or permanent damage even if a small amount of residual liquid freezes.
Second, strong acid resistance. Since the exhaust gas contains acidic media, which can cause the protective adhesive to deteriorate or the pressure-sensing element to be damaged, the sensor is required to pass various acidic media tolerance tests, such as acid dripping, acid evaporation, and acid pressure cycling tests.
Third, resistance to iodomethane. Since iodomethane may be present in the tubing connected to the sensor, it can cause the protective adhesive to deteriorate or the pressure-sensing element to be damaged. Therefore, the sensor must be able to pass the iodomethane evaporation resistance test.
Fourth, strong resistance to temperature shock. Due to the different road conditions and environments in the application, the operating temperature of the product may deteriorate (such as rapid temperature changes or sustained high temperatures). Therefore, the sensor needs to withstand different types of long-term temperature tolerance tests (such as temperature shock durability from -40 degrees to 140 degrees and high temperature durability tests at 140 degrees).
