HG400 Series Process H2S Analyser

Measures H2S in natural gas, fuel gas, biogas or LPG.

HG400 Series Process H2S Analyser
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Duty: To measure the concentration of H2S in a process gas stream.

The principle of operation is as follows. A reel of paper tape impregnated with lead acetate is exposed to the gaseous process sample in the sample chamber. Hydrogen sulphide (H2S) in the process sample reacts with the lead acetate, after acidification, to form lead sulphide (PbS), a brown compound that stains the tape. The higher the concentration of H2S the darker the stain. A focused LED and single photo detector system continuously measures the darkening stain and the analyser reports this as a 4-20mA output of the concentration of H2S.

Incremental measurements are made on the same spot until saturation occurs, when the tape is advanced to a fresh portion of tape. This reduces tape usage and avoids the need for frequent zero or span calibrations.

The benefits of this technology can be summarised as follows:


  • As the measurement is specific to H2S, there will be no interference from other sulphur components
  • A continuous analyser with response times as low as 10 seconds
  • The instrument has a wide range capability, measuring between 0-50ppb to 0-100% H2S and a sensitivity of 5ppb H2S
  • The humidifier has a very low volume allowing response times as low as 10 seconds
  • Configuration of the system is via a touch screen which eliminates the need to open the enclosure.
  • Single point calibration results in lower running costs
  • A compact flash card allows for remote evaluation and diagnostics
  • Capital investment is minimised as up to four detection modules can be run from one controller
  • Multi-streaming capability of up to 4 streams per analyser
  • Suitable for gas group IIC environments.

With its wide-ranging ability to measure H2S from % levels down to ppb levels, the HG400 range of H2S process analysers can be utilised in many process industries, including:


  • Natural Gas pipelines
  • Reformer recycle gas
  • Offshore gas production
  • Fuel gas monitoring
  • Sour gas treatment plants
  • Gas processing
  • Biogas





Measurement principle 





C++ Windows XPe based, SIL 2 certified

Measurement range 


Between 0-50ppb H2S to 0-100% H2S

Typical ranges


0-100 ppb, 0-1 ppm, 



0-50 ppm, 0-3000 ppm



± 1.5% full scale

Response time


From 10 seconds



Up to 4 detection modules






1 x measurement alarm



1 x instrument failure alarm



Optional low flow alarm



Optional paper break/motor failure alarm

Area classification 


ATEX approved, Ex d [ia] IIC T4 

Ambient temperature 


-20°C to +40°C 

Tape life 


Up to 90 days depending on application.

Weather protection 











120 / 240 VAC 50 / 60 Hz

Power rating 


40 VA

Process sample 


Max pressure 1.5 to 4.0 barg 



Flow rate 0.15 to 0.3 l/min




Process connections 


⅛” OD inlet, ¼” NPT female vent 

Analyser vent 


To Atmospheric, no back pressure



30 Kg



378(w), 975(h), 235(d) mm