PID (Photoionization Detector) sensors detect gas concentrations by ionizing the substance to be measured through the energy excitation of an ultraviolet (UV) lamp. Characterized by high sensitivity, they are widely used in the detection of volatile organic compounds (VOCs).
The ultraviolet (UV) lamp energy of PID sensors typically includes 9.8 eV, 10.6 eV, and 11.7 eV, which should be selected according to the ionizing potential (IP) of the target gas. The lamp energy must be higher than the gas’s IP for effective detection. For example, the IP of formaldehyde (HCHO) is 10.87 eV, so a lamp source of 11.7 eV is required for its measurement—a 10.6 eV lamp source cannot detect formaldehyde.
High humidity (>90% RH) may cause water condensation on the ultraviolet lamp window, affecting readings. PID sensors are typically used in dry environments or equipped with moisture-proof designs.
When exposed to high-concentration (e.g., >1000 ppm) or high-boiling-point (e.g., oils, aldehydes, aromatic hydrocarbons) VOC environments, PID sensors may accumulate ionization byproducts or condense/adsorb non-volatile residues (e.g., silicone oil, H₂S) on the UV lamp window. This reduces UV transmittance, leading to signal attenuation, prolonged response time, and decreased sensitivity. Prolonged exposure can permanently damage the lamp source. Equipping PID sensors with pump sampling systems minimizes contaminant buildup, mitigates these effects, and extends sensor lifespan.
MaiYa Sensor Tech, sharing useful gas detection tips.
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