In today's fast-paced society, the rapid development of science and engineering technology necessitates monitoring the application requirements of classical physical quantities of different sizes in various industrial applications. Piezoresistive pressure sensors utilize the piezoresistive effect of single-crystal silicon. Using a single-crystal silicon chip as the elastic element, an equivalent resistance is diffused along a specific direction on the single-crystal silicon film using integrated circuit technology. These resistances are connected to form a bridge circuit, and the single-crystal silicon chip is placed inside the sensor cavity. When the pressure changes, the single-crystal silicon undergoes strain, causing the strain resistance directly diffused onto it to become proportional to the measured pressure. The bridge circuit then obtains the corresponding voltage output signal. What are the structure and characteristics of this pressure sensor?
I. Pressure Sensor Structure
Piezoresistive pressure sensors use integrated circuit technology to integrate a resistive element onto a single-crystal silicon thin film, creating a silicon piezoresistive chip, which is then fixed in a housing with electrode wires leading out. Piezoresistive pressure sensors, also known as solid-state pressure sensors, differ from bonded strain gauges. While they require an elastic sensing element to indirectly sense external force, they directly sense the measured pressure through the silicon film.
The "pressure" measured in this context refers to the "pressure" in physics, an important parameter reflecting the state of matter. Pressure measurements include surface pressure, absolute pressure, negative pressure, and vacuum. Industrially used pressure readings are mostly surface pressure, the difference between absolute pressure and atmospheric pressure. Therefore, absolute pressure is the sum of surface pressure and atmospheric pressure. If the measured pressure is lower than atmospheric pressure, it is called negative pressure or vacuum.
In terms of working principle, pressure measurement sensors are divided into piezoresistive pressure sensors, piezoelectric pressure sensors, piezomagnetic pressure sensors, capacitive pressure sensors, and Hall effect pressure gauges, etc.
Piezoresistive sensors are devices made by diffusing resistors onto a semiconductor substrate, utilizing the piezoresistive effect of semiconductor materials. The substrate can be used directly as the sensor element, and the diffused resistors are connected to a bridge circuit within the substrate.
When the substrate deforms due to external force, the resistance value changes, and the bridge circuit will produce a corresponding unbalanced output. The substrates (or thin films) used as piezoresistive sensors are mainly silicon chips and germanium chips. Silicon piezoresistive sensors using silicon chips as the sensing material are attracting increasing attention, especially solid-state piezoresistive sensors used for measuring pressure and velocity.
II. Characteristics of Pressure Sensors
1. High-frequency response, f0 up to 1.5MHz;
2. Small size and low power consumption;
3. High sensitivity and good accuracy, capable of measuring with an accuracy of 0.1%;
4. No moving parts (sensitive parts and conversion parts are integrated).
What are the structure and characteristics of pressure sensors? For sensor companies, opportunities and challenges coexist, but more Chinese sensor companies are moving in the right direction. With the advancement of the Industrial Internet of Things and intelligent manufacturing, I believe that more excellent domestic sensor companies and products will emerge.
