H2S Analyzer – Model 331S

This simple design by Envent Engineering utilizes a lead acetate based detection system that provides a linear and interference-free output of the H2S or optional Total Sulfur concentration.


  • Fast response times using Rapid Response Algorithms (RRA)
  • No interference from other components in the sample
  • Low power consumption
  • Extended tape life of 60-90 days
  • Measures up to 5 times the calibrated range
  • Interference-free Lead acetate sensor
  • Quick delivery – as fast as 1 to 2 days for standard systems
  • Full field service & training available


Common applications include:

  • Sales Gas
  • Plant Inlet
  • Pipeline Monitoring & Blending
  • H2S Scavenger Systems
  • Wellhead Monitoring
  • Acid Gas
  • Fuel Gas Monitoring
  • Bio Gas


Power 12-24 vdc @ less than 3 watts or 100-240 VAC, 50/60 HZ
Electrical classification Class 1, Div 2 Groups A, B, C & D certified to CSA standards.
Ambient Temperature 0-50 ˚C (32 to 122 F). Contact for other requirements.
Output Ranges Standard ranges: 0-5ppm to 0-100ppm, higher ranges
without dilution available upon request.
Custom ranges: < 5000ppb and up to percent level H2S.
Response time 20-sec alarm
Accuracy 1.5% of full scale, (3% for Total Sulfur or Dilution),
1.5% repeatability
Inputs Four digital inputs individually configurable.
Outputs • Dual isolated 4-20 mA (loop power required).
• Modbus serial RS-232 & RS-485 (Ethernet available)
• Four 5 amp SPDT alarm relays (high reading, high high reading, low tape, low pressure, low temperature, fault).
• Four solid state solenoid drivers ( auto cal, total sulfur, stream switching, valve actuator)
Displays 128 x 64 Graphic Display
Menu is scrolled by internal button
Dimensions 13″W x 15″H x 8″L
(33.02 W x 38.1 H x 20.32 L cm)
Standard system and 331S are mounted on a 24″W x 16″H x ¼”
(60.96 W x 40.64 H x 0.635 L cm) thick anodized panel.
Configuration Software Windows® software for customer configuration, archive
retrieval, and Modbus mapping.
* Product specifications subject to change without notice
to improve reliability, function, design, or otherwise.

Optional Equipment

SDS Dual Stream The 330SDS Analyzer measures two streams at the same time.
Total Sulfur Total Sulfur furnace converts all sulfur compounds to H2S
which allows the analyzer to measure Total Sulfur.
CO2 Dual-beam IR bench. CO2 concentration is displayed on the
second line of display and can be configured as a 2-20 mA
analog output. CO2 ranges from 0-20% to 0-100%
Stream Switching Allows switching of four (4) input streams or from H2S to
Total Sulfur measurement.
Dilution Allows measurements up to 30% H2S using permeable
membrane dilution.
Liquid Sampling Liquid sample system to measure H2S in Hydrocarbon
liquids or water.
Custom Systems Envent can design custom integrated systems to meet
application requirements.