Principle of Operation
UV sensors primarily rely on the photoelectric effect, where UV photons strike a photosensitive material, exciting electrons and generating an electrical current or causing a change in resistance. The resulting electrical signal is proportional to the intensity of the incident UV radiation.
The two main types based on this principle are:
- Photodiode UV Sensor: Measures the current generated when UV light hits a specialized photodiode (often made of wide bandgap semiconductors like Silicon Carbide (SiC) or Gallium Nitride (GaN), which are less sensitive to visible light).This is the most common and accurate type.
- Photoconductive/Photoresistor UV Sensor: Measures the change in resistance of a semiconductor material when exposed to UV light.
UV Spectrum and Sensor Types
The UV spectrum is divided into three ranges based on wavelength and energy:
| UV Type | Wavelength Range (λ) | Characteristics & Source | Sensor Applications |
| UVA | $315 – 400\text{ nm}$ | Long-wave UV, responsible for tanning. Not blocked by common window glass. | Environmental monitoring, smart sunscreen products, UV curing (adhesives, inks). |
| UVB | $280 – 315\text{ nm}$ | Medium-wave UV, causes sunburn. Mostly absorbed by the ozone layer. | UV Index measurement, health/medical phototherapy, plant growth monitoring. |
| UVC | $100 – 280\text{ nm}$ | Short-wave, germicidal/sterilizing UV. Completely absorbed by the atmosphere. | UV sterilization devices, water purification, flame/arc detection. |
Most UV sensors are designed to be selectively sensitive to one of these bands (e.g., an “UVC Sensor”) using specialized materials and optical filters.
Applications
UV sensors are used across numerous fields where the measurement or control of ultraviolet radiation is necessary:
- Environmental Monitoring: Measuring the UV Index (a measure of the strength of sunburn-producing UV radiation) for public health warnings and meteorological data.
- Industrial Processes: Monitoring the intensity of UV lamps used in UV curing (hardening of resins, adhesives, or inks) and UV sterilization (water or air purification).
- Security and Safety: Flame and Arc Detection, as combustion generates UV radiation.11 Used in high-security settings or industrial sites.
- Health and Medical: Monitoring UV dose during phototherapy treatments for skin conditions and in wearable devices to track personal sun exposure.
- Astronomy: Used in space-based telescopes to study objects emitting UV light.
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