Monday, February 22, 2021

HNU PID Lamp Sensitivity


The Photoionization Detector (PID) is very sensitive and provides a response to a wide range of organic and some inorganic compounds at part per billion (ppb) levels. The HNU PID consists of an ultraviolet lamp and an ion chamber.  The detector measures the concentration of gases present in a sample  using the method of pbotoionization.Photoionization occurs when a molecule absorbs a photon (light energy) of sufficient energy, creating a positive ion and an electron as shown below:
R  + hn  = R+  + e-
The sample drawn into the ion chamber is exposed to photons generated by the ultraviolet lamp. Molecules in the sample with ionization potentials less than or equal to the energy level of the lamp are ionized. The ionization potential is that energy in electron volts (eV) needed to free an electron from a molecule. A positively biased accelerator electrode repels these ions, causing them to travel to the collecting electrode, where an analog signal proportional to the concentration of the sample is generated.  The signal is amplified to provide an analog output for graphic recording or electronic integration. Ultraviolet lamps are available in four energies; 8.3, 9.5, 10.2, 10.6 and 11.7 electron volts (eV).  Our lamps have the longest lifetime and operating hours in the industry.

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