EM-5L Flue Gas Analyzer (Ultra-low Range)


EM-5 flue gas analyzer is a self-developed gas analysis product of multiple return light path. The gas analyzer is based on DOAS and chemometric algorithms (PLS), able to measure SO2, NO, NO2, O2, NH3, CO, CO2, Cl2, O3, H2S, HCl, CH3I, etc. With high accuracy and reliability, low operating costs, fast response time, wide measurement range and application fields, it has achieved even surpassed similar products home and abroad.

Technical Principle

EM-5 flue gas analyzer (ultra-low emission monitoring) uses the long optical path UV DOAS technology. Its optical technology platform consists of light source, white cell gas chamber, optical and spectroscopic (including diaphragm, holographic grating, linear array detector) and other optical components. As shown in figure.

Ultraviolet light is sent by the photosource through the optical window into the white cell gas chamber (optical path 5-15 meters, adjustable) , and absorbed by the sample gas flow through the white pool gas chamber. The light carrying sample absorption information gathers through lens coupled into the fiber and then transmits through the optical fiber into the spectrometer. After light splitting and photovoltaic conversion, absorption spectrum is obtained and analyzed to calculate the concentration of the related components in gas.

Product Feature

High measurement accuracy

  • The minimum detection limit of SO2 , NO2, NO can be 1mg/m3 (15m optical path)
  • Ultraviolet has no moisture absorption, undisturbed by moisture and dust.
  • No cross interference between the gas being measured (see table 1)
  • NO and NO2 can be measured at the same time, dispense  with converter

High reliability

  • White cell + DOAS + PLS technology, small amount of zero drift and span drift
  • Modular design
  • No optical moving parts and no vibration influence
  • Strong gas cell, low cost
  • Spectrum automatic adjustment technology, long free maintenance cycle
  • Light source adopts the pulse source, the service life is 10 years


Measuring TechniqueDOAS(SO2、NOx),Electrochemistry(O2)
Measuring Range0-20-1000ppm(SO2、NOx),0-25%(O2)
Linearity Error≤±1%F.S.
Zero Drifting≤±2%F.S./7d
Measuring Range Drift≤±2%F.S./ 7d
Response Time< 25s( T90 )
Warm-up TimeNone
Relay Output14
Binary Input6
Analog Output4×4 -20mA
AnalogInput2×4 -20mA
Digital CommunicationRS232/ RS485 /GPRS
Enclosure RatingIP65
Ambient Temperature-10ºC~40ºC
Ambient Humidity0% Rh~95%Rh


  • Low detection limit and temperature-drift
  • Getting NOx by directly measuring NO and NO2 without NO2→NO converter
  • No interference of particulate matter, moisture and other factors
  • No optical moving parts, high reliability,  no interference to the measurement by field vibration Using return light path and high quality spectrograph, the minimum measuring range is 0-20ppm,
  • Lowest detection limit is 200ppb


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