Envent’s Patented Dual Sensing – Model 331SDS

This unique design utilizes Envent’s interference free sensing tape to measure “Two” gas streams concurrently. Analysis streams can be H2S/Total Sulfur or High Range / Low Range H2S.


  • 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


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 15″W x 15″H x 8″L
(38.1 W x 38.1 H x 20.32 D cm)
The Model 331SDS is mounted on a 32″W x 24″H x ¼”
(81.3 W x 60.1 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.


The 331SDS is able to measure 2 streams of H2S in natural gas and other
process gases at the same time. This unique analyzer has dual 4–20 mA outputs, dual measurement alarms, plus trouble and fault alarm relays. The 331DS displays H2S concentration in user specified units (ppb, ppm, grams, %, mg/M3) and as well will auto-range to 5 times the lower calibrated range.

The 331SDS is available with a number of sample systems and accessories to handle various applications such as high range H2S, Total Sulfur or H2S in liquids.