1. Definition and Function of Sensors
•Definition: A device that can sense the physical/chemical quantities being measured and convert them into usable electrical signals, serving as the frontend entry for information digitization.•Two Core Functions 1Information Detection: The sensitive element interacts with the environment to capture parameter changes in real-time. 2Signal Conversion: Converts non-electrical quantities to electrical quantities (resistance, voltage, current, etc.) for easier subsequent processing.
2. Core Components
| Module | Function | Key Examples |
|---|---|---|
| Sensitive Element | Directly senses the measured quantity, determining range and sensitivity | Thermocouple junction, strain gauge metal foil |
| Conversion Element | Converts sensitive output to electrical parameters | Hall element, piezoresistive membrane |
| Signal Conditioning | Amplification, filtering, linearization, ADC | INA125 instrumentation amplifier → 0-5 V/4-20 mA |
3. Quick Classification
3.1 By Operating Principle
| Category | Principle | Representative Sensors | Key Indicators |
|---|---|---|---|
| Electrical | Changes in resistance/capacitance/inductance | Strain gauge, thermistor | ±0.1 % FS, -50~300 ℃ |
| Magnetic | Hall/magnetoresistive effect | Hall speed sensor | ±1 rpm |
| Optical | Photoelectric/interference/ToF | CCD, ToF depth camera | 1.4 µm pixel, mm-level ranging |
3.2 By Measured Physical Quantity
| Physical Quantity | Typical Sensors | Range/Accuracy | Applications |
|---|---|---|---|
| Mechanical | MEMS piezoresistive pressure, piezoelectric accelerometer | 0-100 MPa / 0.1 Hz-10 kHz | Engine knock, bridge health |
| Thermal | K-type thermocouple, PT100 | -200~1300 ℃ / ±0.1 ℃ | Furnaces, laboratories |
| Chemical | Electrochemical O₂, semiconductor VOC | ppm level, 2-5 years lifespan | Environmental monitoring, ventilators |
| Biological | Glucose enzyme electrode, DNA chip | <10 s response | Blood glucose meters, gene sequencing |
4. Advanced Forms
| Form | Technical Highlights | Size/Performance | Scenarios |
|---|---|---|---|
| MEMS | Micro-mechanical + IC integration | 3×3 mm, ±2000 °/s | Smartphone gyroscopes, drone barometers |
| Optical Fiber | Bragg grating distributed measurement | 1 m spatial resolution, 300 ℃ temperature resistance | Oil well logging, dam strain |
| Smart Sensors | Edge AI vision | <50 ms latency | Industrial quality inspection, AGV navigation |
5. Summary of Physical Effects
| Effect | Brief Principle | Example Sensors | Performance Tips |
|---|---|---|---|
| Piezoelectric Effect | Stress → Charge | Pressure, acceleration, microphone | Quartz, PZT ceramics |
| Photoelectric Effect | Photon → Electron | Photodiode, CCD | Visible light ~ near-infrared |
| Thermoelectric Effect | Temperature difference → Voltage | Thermocouple, infrared thermal imager | K type -200~1300 ℃ |
| Magnetoresistive Effect | Magnetic field → Resistance change | Magnetometer, hard disk read head | µT level resolution |
6. Chemical Sensing Mechanisms
| Mechanism | Output Signal | Lifespan/Cross-Sensitivity | Example |
|---|---|---|---|
| Electrochemical | Redox current | 2-5 years, low cross-sensitivity | Glucose pen electrode |
| Semiconductor Gas Sensitive | Resistance change | ppm level, prone to cross-sensitivity | SnO₂ combustible gas alarm |
| Optical Chemical | Fluorescence/colorimetric intensity | No electrodes, long-term drift | Water quality COD test strips |
7. One-Sentence Summary
> “Sensitive + Conversion + Conditioning” trio,> “Electrical, Optical, Magnetic, Thermal, Pressure” five effects,> “MEMS, Optical Fiber, Smart” three trends,> Choosing the right principle = Choosing the right sensor!
