Gigahertz Optik - Light Measurement Solutions

Optical radiation primarily in the UVC/UVB spectral region from ~170 to 310 nm is known to kill or stop the reproduction capabilities of bacterium, mold, fungus and other microorganisms. Early work by Luckiesh, Holladay, Taylor in the U.S., DIN in Germany and others produced a germicidal spectral effectiveness function showing that in general the spectral zone for maximum germicidal killing is between 253.7 and 265 nm. The energy levels required for germicidal/bacteridical effect vary depending on the type of organism. The low-pressure Hg arc source with >90% of its output at 253.7 nm is so often used to deliver the UV energy that it is known as the 'germicidal lamp'. The medium-pressure Hg arc lamp is also gaining favor due to its broader spectral distribution.

UVGI (Ultraviolet germicidal irradiation) is currently employed in air, water and material disinfection applications. In the water industry, UVGI systems are placed in the final stages of waste water and potable water treatment. UVGI is a 'greener' disinfection solution than chlorine or other ozone depleting chemicals. UVGI sources are also mounted into air ducts, chambers or on walls in the upper room area to kill viruses, TB germs, molds and fungus. UVGI has recently been employed in the war on bioterrorism due to its ability to kill anthrax and small pox. Other uses for the sterilizing effects of UVGI can be found in the food, beverage and packaging industries as well in medical applications. Since energy increases as wavelength decreases, short wave UVGI at 253.7 nm is very good at effecting molecular level disruptions in everything in its path. Unfortunately this includes UVGI measurement devices. Detectors used to measure UVGI (W/cm²) and energy dose (J/cm²) must be designed with appropriate materials and components incorporating protective technologies to avoid degradation due to long term exposure. In some cases involving liquid disinfection the detector must be sealed and made waterproof for submersion into the fluid.

Since UV radiation is invisible to the human eye measurement with a good quality radiometer is the only way to know or monitor the output level for process control, dosimetry and also to assess health hazard risk. The UV radiometer should offer the functions and features required to fulfill the application requirements. The detector used in concert with the meter should be designed and configured to match the target application. A qualified UV broadband detector will offer:

• Coverage of the required spectral range with the appropriate spectral shape and minimal response outside this zone
• The proper measurement geometry for the quantity under test
• Good stability under long term use
• Calibration in the appropriate units with calibration correction to a specific source for added accuracy when required

Gigahertz-Optik has developed the solid-state solar blind photodiode UV-3718 detector for this application.

Additional information from our Products section:
        UV-C Irradiance Light Detector: UV-3718
        Possible Optometer: X9₁₁_, P-9710

Additional information from our Tutorials section: VI.3. UV-Disinfection and Lamp Control

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