Pressure Sensors

The elements or instruments measure the liquids or gas pressure. Pressure sensors convert the actual pressure into electronic signals that can be easily read. In addition to directly measuring pressure, these sensors can also infer other metrics such as the flow of fluids/gases, velocity, water levels, and even altitude. Known by a variety of names - including pressure transducers, pressure transmitters, pressure senders, pressure indicators, pressure gauges, and manometers - these versatile devices are integral to numerous sectors, from aerospace and healthcare to the petrochemical industry.

History of Pressure Sensor Development

The development of MEMS chips largely determines the pressure sensor development. It is essentially semiconductor sensors. C.S. Smith discovered the piezoresistive effect of silicon and germanium in 1954.  This effect meant that when an external force is applied to a semiconductor material, its resistance would change significantly. Based on this principle, a strain resistor was glued to a metal film to convert the force signal into an electrical signal, thus enabling pressure measurement.

This marked the birth of piezoresistive pressure sensors. Subsequently, along with the silicon diffusion technology, each anisotropic corrosion technology and after the 80's micro-processing technology, gradually bring the pressure sensor to the micron level and the large volume development stage.

How does Pressure Sensor Work?

The pressure sensor works by converting the applied pressure into electrical signals. And they measure and interpret electrical signals through control system and user interface. There are many types of pressure sensors, while most of them have the following working principles.

• Piezoresistive: This type uses diaphragm (usually made of silicon or a metal)，which leads to deformation in case of applied certain pressure. The resistance embedded strain gauges or piezoresistors have been changed due to the deformation. Then, it is converted into an electrical signal proportional to the applied pressure.

• Piezoelectric: Piezoelectric materials (such as quartz) are used among piezoelectric pressure sensors, which generates an electric charge when applied to pressure. The generated charge is proportional to the applied pressure. Meanwhile, it can be measured as an electrical signal.

• Capacitive: Capacitive pressure sensors have a diaphragm between two conductive plates. Once applied certain pressure, the shape of diaphragm and the distance between the plates will be changed, subsequently altering the capacitance. Meanwhile, changes in capacitance are measured and converted into an electrical signal.

There are just a few types of pressure sensor. Different types of pressure sensors have different advantages and disadvantages. The performance of pressure sensor depend on specific applications, required accuracy, sensitivity and environment conditions. However, it is worth mentioning that different types of pressure sensors have the same basic woring principle and function. This means pressure sensors convert the applied pressure into electrical signals for measurement and analysis.

Piezoresistive Pressure Sensors Working Principle

• Piezoresistive Effect

Piezoresistive pressure sensors operate based on the piezoresistive effect. When pressure is applied to the diaphragm, it deforms, causing mechanical strain in the piezoresistive elements. The strain leads to a change in the resistance of the piezoresistive elements. This change in resistance is proportional to the applied pressure.

• Wheatstone Bridge Configuration

Wheatstone bridge circuit measures the change in resistance. The Wheatstone bridge consists of four resistors, with the piezoresistive elements acting as two of the resistors. When pressure is applied, the resistance change in the piezoresistive elements unbalances the bridge circuit, inducing a voltage output proportional to the pressure.

• Signal Processing

The output voltage from the Wheatstone bridge is then processed by signal conditioning circuits. The amplified and converted signal can be displayed as pressure readings on a display or transmitted to a control system for further action.

Common Analog and Digital Outputs for Pressure Sensors

Analog: 0-100mV, 0-5V, 0-10V, 4-20mA, etc.

Digital: IIC, SPI, CAN, RS485, etc.

In essence, analog and digital signals are methods of signal transmission. The two can be converted into each other.

How Does a Pressure Sensor Output a Digital Signal?

When a pressure sensor detects pressure change, it generates an analog signal representing the pressure value. The analog signal is converted into a digital signal through the below process:

• Sampling: Analog signals change continuously, while digital signals are discrete. sampled analog signals at regular intervals convert a continuous analog signal into a discrete digital signal.

• Quantization: The sampled values will be quantized. The continuous amplitude range is discrete levels. Each level corresponds to a numeric value. These binary form digital values are digital signal. This process is usually accomplished by an analog-to-digital converter (ADC).

Digital signals are transmitted through cables with corresponding communication protocols (such as SPI, I2C, 485, etc.). Digital signals can be processed by digital systems such as computers. Digital signal processors (DSPs) can also analyze, store, and transmit.

How to Choose A Suitable Pressure Sensor?

Choosing a suitable pressure sensor requires determining the following factors:

• Pressure Type: Pressure type can be divided into gauge pressure (G), sealed gauge pressure (SG), absolute pressure (A), and differential pressure (D). The main difference is that different pressure points are used as reference points for the sensor zero point. Application requirements and environmental conditions are important considered factors.

• Pressure Range: Make sure the pressure range provided covers the pressures likely to occur in the working application. It's suggested that the normal working pressure should be near the middle of the selected measurement range. On the one hand, this can maximize accuracy and reduce errors. On the other hand, possible accidental pressure changes will not cause the sensing element to be overloaded and damaged.

• Size: The installation environment determines the size of pressure elements, such pipes diameter, equipment size, etc. If you cannot determine the size of the installation space, it will cause installation problems for the pressure element. MicroSensor provides ф19mm, ф17mm, ф15mm, ф12.6mm and other optional diameters. The height is also optional for different applications, such as 6.5mm and 11.5mm. Customized sizes are also available upon customer request.

• Operating Temperature: The working temperature range refers to the pressure sensor that can work without failure at a certain temperature. Some pressure elements' operating temperature range can reach -40~125℃.

• Special Working Conditions: Special working conditions are mainly the requirements of the installation environment. If there are factors such as high temperature, high pressure, corrosive media in the environment, you need to choose a pressure sensor with corresponding materials and protective measures. According to special working conditions, MicroSensor will analyze the actual needs of customers and provide the most suitable customized product solutions.

• Pressure Measurement in Oil and Gas

Pressure sensors play a crucial role in oil and gas applications, encompassing a wide range of pressure types during the measurement process, including gauge, absolute, differential, high pressure, and micro differential pressure, among others. Our engineers possess extensive experience in this sector and possess a deep understanding of the challenges and intricacies involved in oil and gas processes. By applying our cutting-edge technology, we provide pressure measurement solutions for our customers to ensure process and product safety in the oil and gas industry.

• Pressure Sensors Applied in Food

The containment risk and cleanness difficulties are widely regarded as a matter of significant public concern during food and beverage processing. The vital is each cans, bottles, bags, or boxes leaving the factory are of the highest quality and health, and follow strict regulatory criteria. The reputation and profit of the company rely on these criteria.

It is necessary to establish complete control and procedure for smooth and efficient operation. Precision and reliable pressure sensors play vital role in process optimization. Whether measuring level of the fermentation tank or discharge pressure, advanced pressure sensors contribute to the security of food and beverages.

• Pressure Sensors in Industrial Automation

Pressure sensors in industrial automation work by measuring pressure, transmitting the measured signals to control systems, facilitating safety monitoring, and process optimization within pneumatic and hydraulic systems.  

Micro Sensor tailored monitoring solutions aiming to maximize energy efficiency and improve product quality of our customers. In addition, the inner professional R&D team is committed to provide specialized piezoresistive oem pressure sensor to meet different demands. If you have any questions or suggestions, please feel free to leave a message. Micro Sensor’s sales engineers will respond within 24 hours, ensuring timely and personalized help.

The main production processes of a pressure sensor are gluing, binding, diaphragm welding, oil filling, sealing, pressure impact, aging, temperature compensation, resistance adjustment and inspection.

The quality of sensors is not only influenced by its properties, but also by its production process. The R&D and manufacturing of industrial pressure sensors of Micro Sensor is originally from the 1970s, with our production line showing the development of China's sensor technology. Over the years, the production line has been expanded and upgraded several times, representing the great progress of the industry.

At present, Micro Sensor has its own advanced manufacturing site, realizing digitization, automation, and flexibility and manufacturing series star products including customized MPM280 Series, high-performance MPM281 Series, and general MPM288 Series, which conform to the highest quality criteria to meet the client's satisfaction.

MicroSenor Piezoresistive Pressure Sensor Advantages

• Automation Manufacturing Equipment

The fully automatic production process better ensures comprehensive performance. The automated production line ensures pressure sensors stability and consistency and meets customers' order needs in different batches. MicroSensor uses advanced automatic production equipment in key processes such as bonding, diaphragm welding, oil filling, sealing, and compensation.

• Mature Production Technology

The level of manufacturing technology has a crucial impact on product performance. As a pressure sensor manufacturer with decades of production experience, MicroSensor ensures the accuracy and reliability of pressure elements through the following process technologies: 

1. Pressure Cycling and Aging: The two processes mainly solve the product's long-term stability problem. All products are aged and tested through a simulated pressure and temperature environment.

2. Automatic Compensation Test System: Temperature compensation mainly solves the temperature drift of the silicon chip. Compensation testing reduces or offsets the drift in the output signal of a piezoresistive pressure sensor as a function of temperature. It confirms whether product meets performance indicators. All pressure sensors implement output performance testing by multi-temperature point under advanced testing equipment and systems.

3. Laser Trimming: The laser cutting process trims the resistance value to the preset value. Precise etching compensates for the resistance of the corresponding resistor on the ceramic plate. This makes it consistent within the error range with the resistance value provided by the compensation test.

•  Advanced Products

1. Higher Sensitivity

Sensitivity can express the degree of amplification of the input signal by the sensor in practical applications. The piezoresistive pressure sensor can be more sensitive and accurate when detecting small changes in pressure. MicroSensor's higher sensitivity pressure sensor provides more reliable and stable measurement.

2. Smaller Temperature Error

Silicon piezoresistive pressure sensors are temperature-sensitive. At present, Micro Sensor's silicon piezoresistive sensors have fully adopted laser trimming technology and related algorithms. A dedicated processing chip or application circuit performs temperature compensation under software operation. This allows silicon piezoresistive sensors to achieve smaller temperature errors and better stability.

3. Better Long-Term Stability

The main factors affecting long-term stability are its structure, manufacturing process, and environmental adaptability. Micro Sensor's sensors undergo pressure and fatigue tests in strict accordance with process requirements during the production process. The output values of the tested sensors are essentially unaffected even by changes in external temperature and pressure.

4. Customized Configuration Options

MicroSensor offers customization options for pressure type, measurement range, materials, diameter size, etc. Customized pressure elements allow customers to tailor specifications to suit specific application requirements.