For UV and visible light

UV sensors and VIS sensors for laboratory and process

UV sensors and VIS sensors capture irradiance or dose within defined spectral ranges. What governs the selection is the source, the wavelength range, the expected reading, the angular distribution, the mounting position and the electrical interface. This category sorts sensors for hand-held instruments, stationary process monitoring and customer-specific measuring tasks.

Which sensor do I need?

The selection follows two quantities. The spectral range follows the application – in curing processes, the absorption band of the photoinitiator. The measuring range follows the irradiance to be expected, not the instrument. The full selection sequence, with guide values per source, is set out under selecting a UV sensor.

The sensor has to match the spectrum, not just the spectral range. For low-pressure lamps a narrow-band weighting around 254 nm is sufficient, because practically all the UVC output sits in that line. Medium-pressure lamps emit broadband across the whole UVC range and require a sensor with a broad, flat UVC weighting calibrated for exactly that lamp type. UVC LEDs – typically 265 to 280 nm – require calibration to their peak wavelength. Without source-specific calibration factors, the same sensor does not deliver comparable values at all three sources. Why that is so is explained under design and error sources of UV sensors.

All sensors ship calibrated with a factory calibration certificate and can be recalibrated at any time; procedures and records are described under UV calibration. For continuous monitoring, inline sensors are available; workplace exposure measurements carry their own requirements for sensitivity and weighting – see workplace exposure measurement. Matching display units are listed under UV meters and radiometers, the interchangeable measuring heads under radiometer sensors and measuring heads. Repair and spare parts are handled under service and repair.

A UV sensor on its own is not yet a measurement. What finally produces a reliable value is a chain: sensor, spectral weighting, amplifier and interface, calibration, mounting position. Any link can shift the result by more than the resolution of the instrument; that is why it pays to design the sensing as a whole.

Besides spectral range and measuring range, two further decisions carry the design:

• Interface. 0–10 V or 4–20 mA for the plant, RS-485 or Ethernet where calibration status and sensor type should travel with the reading – this choice later decides whether a deviation is read as sensor drift or as a process fault.
• Mounting position. The sensor measures what arrives at the sensor, not what arrives at the workpiece. Distance, acceptance angle and window fouling decide whether the two are related.

Monitoring irradiance continuously in a plant calls for different properties than an acceptance measurement: the reading does not have to be most accurate on day one, it has to stay stable for years. How a UV sensor works internally and where its error sources lie is set out under how UV sensors work; the UV sensor finder locates the right sensor by spectral range and measuring task.

• Dose control in UV curing and bonding
• Monitoring of UV irradiation 
• Control of disinfection systems in the packaging industry
• UVC water disinfection, UVC wastewater treatment
• Lamp monitoring and quality assurance in lamp production
• Measurement of workplace safety due to artificial optical radiation
• Photometric measurements
• PLC-control and lamp power regulation

Find the right sensor: The UV Sensor Finder proposes the three best-matching UV sensors and meters by application, wavelength and form factor – with key values, system partner and reasons.