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Industry News As a professional company with over 40 years of experience in sensing technology, Shanxi Tengxing Sensor Technology Co., Ltd. not only focuses on gas sensing but also has a deep understanding of pyroelectric infrared sensors, a crucial motion sensing device. These sensors can "see" changes in heat and are widely used in security alarms, smart homes, automatic control, and other fields.
1. Core Working Principle: Utilizing the Pyroelectric Effect
Pyroelectric infrared sensors operate based on the core pyroelectric effect. You can think of it as a three-step process:
Sensing Temperature Changes: The key component within the sensor is a special crystalline material (such as lithium tantalate or lead zirconate titanate). This material has a property: when its surface temperature changes, the positive and negative charge centers within the crystal shift relative to each other, generating a weak voltage signal across the material.
Key Limitations: Most importantly, it cannot detect constant heat sources, only dynamically changing infrared radiation. This means that a stationary person will not be detected, but movement will be detected by the sensor. Signal amplification and judgment: The weak voltage signal generated passes through a field-effect transistor (FET) inside the sensor for impedance conversion and amplification, ultimately outputting a recognizable electrical signal.
2. Core Components and Collaboration
A complete pyroelectric infrared sensor typically consists of the following components working together:
| Component Name | Functional Description | Why is it important? |
| Pyroelectric Chip | The core sensitive element is responsible for converting temperature changes into electrical signals. | This is the "heart" of the sensor and directly determines its sensitivity and performance. |
Fresnel lens | A plastic lens covering the front of the sensor, with multiple prisms on its surface. | Expands detection range: Focuses infrared radiation from a large area into a smaller spot. |
| Infrared filter | Located in front of the chip, it is usually black. | It allows only infrared light of a specific wavelength (8-14μm) emitted by the human body to pass through, effectively filtering out visible light and other wavelengths of infrared light (such as sunlight and lamplight), preventing interference. |
Matching resistor/JFET | Integrated within the sensor. | Used to convert the high-impedance charge signal generated by the chip into a low-impedance voltage signal and amplify it. |
Workflow Summary:
Human movement → Infrared light changes → Fresnel lens focuses and modulates the signal → IR filter filters stray light → Pyroelectric chip senses temperature change and generates charge → JFET amplifies and outputs the electrical signal.
3. Key Technical Features
Passive Detection: It does not emit any energy, but passively receives infrared radiation, resulting in extremely low power consumption and high safety.
Sensitive Only to Moving Heat Sources: It cannot detect stationary objects, a characteristic, not a drawback, effectively reducing false alarms.
Long Life and High Reliability: It has no mechanically wearing parts and operates reliably.
4.Typical Application Scenarios
Automatic lighting control: Turning on lights in hallways, corridors, and bathrooms when people enter and off when they leave.
Security alarm systems: Infrared burglar alarms in homes and warehouses.
Smart home devices: Automatic sensing for smart toilets, automatic doors, and energy-saving air conditioners.
HDA-243A Pyroelectric infrared sensor
Sensing technology is a crucial way for the world to perceive everything. If you have any questions about sensing technology or need a high-performance gas sensing solution, Shanxi Tengxing Sensing is always your professional partner.
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