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H2S Analyzer with Classic Sample Conditioning System

H2S Analyzer

The OMA H2S Analyzer monitors the UV-Vis absorbance in a continuously drawn liquid/gas sample and outputs real-time hydrogen sulfide concentration.

Harvesting this rich data, the OMA H2S Analyzer isolates the H2S absorbance curve and provides a real-time value for H2S concentration in your process.

H2S occurs abundantly in the world’s fossil fuel reserves and also forms as a by-product in various industrial and biological processes. In order to produce clean-burning fuels, prevent acid rain, protect pipelines and equipment from corrosion, and — most importantly — protect workers from imminent disasters, H2S levels are highly regulated using scrubbers, scavengers, sulfur recovery units, and other removal technologies.

To properly control the level of H2S in fuel, wastewater, or emissions, you need a reliable method of measuring the H2S concentration. Since safety is a major concern, only highly proven solutions are considered. For many years, that meant that customers were stuck with archaic paper tape technology, a maintenance headache with toxic consumables and frequent moving-part hardware failures.

Since its launch in 1994, OMA technology has rapidly replaced the old methods by providing the customer with solid state reliability and superior performance in an affordable package.

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  • Fast, continuous reading
    Analyzer response time is 1 to 5 seconds
  • No false positives
    Interfering chemicals can be corrected for by AAI’s multi components algorithm*
    *Provide sample matrix to AAI for verification
  • Huge dynamic range
    Remains accurate through wide changes in concentration

Safety & Reliability

  • Unattended operation
    Stabilized by Auto-Zero; remote operation optional
  • World's safest H2S analyzer
    Sample fluid never enters analyzer enclosure Learn more
  • Customizable alarms & outputs
    4-20 mA analog outputs; MODBUS; Hart... View technical specs


  • Measure any H2S concentration range
    From 0-10 ppm to 0-100% Learn more
  • Direct analysis of hot/wet sample
    Standard model accepts sample up to 150 °C and 3000 psi
  • Analyzes liquid or gas
    Using appropriate sample conditioning system
  • Up to 4 available measurement benches
    For measuring additional chemicals Learn more

Cost of Ownership

  • No consumables/reagents
    Other than zero fluid
  • Proven low-mainentance
    Only requires monthly optics cleaning
  • Long-life xenon light source
    Averages 5 years between replacement
  • Solid state instrument
    Outlasts competing models due to lack of moving parts


  • Hazardous area certifications
    Class I Div 1 & 2; ATEX; GOST... View certifications
  • No shelter required
    Rugged instrument suitable for outdoor installation


Principle of Operation

To analyze the chemical composition of the sample, the OMA uses an analysis method known as ultraviolet-visible (UV-Vis) spectroscopy. The system measures absorbance from 200nm to 800nm and quantifies the amount of light absorbed by the sample at each integer wavlength; the OMA plots this raw data to visualize a high-resolution absorbance spectrum. Learn more

Spectrophotometer Principle of Operation-Online Process Hydrogen Sulfide H2S Analyzer-H2S Measurement

The OMA uses a long-life xenon light source to transmit a signal through the sample fluid in the flow cell. The signal is carried by fiber optic cables from the analyzer to the flow cell, where the chemical mixture of the sample has unique interactions with the light based on its current composition. Learn more

Optical Assembly-Online Process Hydrogen Sulfide H2S Analyzer-H2S Measurement

H2S Absorbance Spectrum

To measure H2S concentration, the OMA detects the distinctive absorbance curve of pure H2S and mathematically isolates this structure from the total sample absorbance. In accordance with Beer-Lambert Law, the OMA correlates the height of this curve directly to real-time hydrogen sulfide concentration.

Absorbance Curve: Hydrogen Sulfide

Absorbance (AU)
Wavelength (nm)

User Interface

Our proprietary ECLIPSE software processes the raw spectral data to provide real-time concentration readings. The operator can easily navigate between views (trendgraph, spectrum, and more) using intuitive touch-screen navigation. You can also configure alarms, data logging, and outputs. Learn more

ECLIPSE software-Online Process Hydrogen Sulfide H2S Analyzer-H2S Measurement

Inherent Safety

Most analyzers draw the process sample directly into the analyzer enclosure for analysis, which is dangerous if the sample fluid is toxic, explosive, or corrosive. The OMA design is unique: we bring the light to the sample, not the other way around. The sample circulates through the external flow cell, which receives the signal via fiber optic cables. Learn more

Analyzer Safety-Online Process Hydrogen Sulfide H2S Analyzer-H2S Measurement


All OMA models are equivalent in function and performance with identical electronic configurations. The models vary by form factor and materials of construction, each intended for a unique use case.



Wall-mounted process analyzer

  • Indoor/outdoor use
  • ATEX, Class I Div 1/2, GOST...
Learn more


Suitcase process analyzer

  • Carry from site to site
  • Rugged suitcase enclosure
Learn more


Rackmount process analyzer

  • Fits standard 19" rack
  • Ideal for lab/shelter
Learn more

Explosion-Proof Models

The OMA-300 is offered in two explosion-proof formats:

Exp (Purged) Explosion-Proof OMA-300


Eexp systems are purged and pressurized using a certified air-purging device. This method ensures that toxic/explosive gas is not allowed to accumulate inside the enclosure, and is ideal when instrument air is available.

Exd (Cast Aluminum) Explosion-Proof OMA-300


Eexd systems are contained within certified explosion-proof cast-aluminum enclosures. This method is more practical if the installation is remote or utilities are unreliable.


The OMA is built for direct analysis of the hot/wet sample, thus simplifying the scope of the sample system and retaining high sample integrity. From our vast experience in sampling design, we know that applications can be similar but are rarely identical. For this reason, we design and build sample conditioning systems on a project basis, working from the process to the drawing board.


Note: All performance specifications are subject to the assumption that the sample conditioning system and unit installation are approved by Applied Analytics. For any other arrangement, please inquire directly with Sales.

Measurement Principle Dispersive ultraviolet-visible (UV-Vis) absorbance spectrophotometry
Detector nova II™ UV-Vis diode array spectrophotometer
Spectral Range 200-800 nm
Light Source Pulsed xenon lamp (average 5 year lifespan)
Signal Transmission 600 μm core 1.8 meter fiber optic cables
Other lengths available
Path Length Application-dependent
Sample Conditioning Custom design per application
Analyzer Calibration If possible, analyzer is factory calibrated with certified calibration fluids; no re-calibration required after initial calibration; measurement normalized by Auto Zero
Reading Verification Simple verification with samples and self-check diagnostic
Human Machine Interface Industrial controller with touch-screen LCD display running ECLIPSE™ Software
Data Storage Solid State Drive
Analyzer Environment Indoor/Outdoor (no shelter required)
Ambient Temperature Standard: 0 to 35 °C (32 to 95 °F)
Optional: -20 to 55 °C (-4 to 131 °F)
To avoid radiational heating, use of a sunshade is recommended for systems installed in direct sunlight.
Sample Temperature Standard: -20 to 70 °C (-4 to 158 °F)
Optional: up to 150 °C (302 °F) with cooling extensions
Contact AAI for temperatures above 150 °C (302°F)
Sample Pressure Using standard flow cell: 206 bar (3000 psi)
Using immersion probe: 100 bar (1470 psig)
Electrical 85 to 264 VAC 47 to 63 Hz
Power Consumption 45 watts
Standard Outputs 1x galvanically isolated 4-20mA analog output per measured analyte(up to 3; additional available by upgrade)
2x digital outputs for fault and SCS control
Optional Outputs Modbus TCP/IP; RS-232; RS-485; Fieldbus; Profibus; HART;
Select analyzer type: OMA-300 Wall-Mounted Analyzer
OMA-206P Portable Analyzer
OMA-406R Rackmount Analyzer
H2S Accuracy in Liquid
Example ranges below. Custom ranges available.
0-100 mg/L:  ±1% full scale or 1 mg/L*
*Whichever larger.
H2S Accuracy in Gas
Example ranges below. Custom ranges available. Accuracy may be higher at higher pressure.
0-10 ppm (@1 bar):  ±1 ppm (Increased pressure will yield increased accuracy);  ±0.2 ppm (@5 bar)
0-100 ppm:  ±1% full scale or 1 ppm*
0-10,000 ppm:  ±1% full scale
0-100%:  ±1% full scale
*Whichever larger.
Standard Design General Purpose
Available Options ATEX, IECEx, EAC
Please inquire with your sales representative for additional certifications (CSA, FM etc.).

Technology Comparison

Below we compare the most popular solutions for process H2S analysis.

Click any cell or row for more information.

Paper TapeTunable Diode LaserGas ChromatographOMA H2S Analyzer
20-180 seconds. Actual response time depends on H2S level.
less than 10 seconds
5-10 minutes
less than 10 seconds
Moisture Interference?  NONE HIGH NONE NONE
Moisture absorbance is a serious problem at the measurement wavelength.
Water does not absorb at 200-240 nm wavelength region.
Only suitable for low level H2S. Tape saturation occurs above 1000 ppm and requires error-prone dilutions.
Designed for levels under 500 ppmv. Signal saturation occurs at higher levels w/ no alternate wavelengths.
Any range from 0-10 ppm to 0-100%; modify your system's range at any time. Learn more
Additional Measurements?  NO NO YES YES
The special tape is only sensitive to H2S. Total sulfur requires a large furnace.
Each TDL unit measures one chemical.
Up to 4 additional measurement benches (e.g. SO2, MeSH) per unit. Learn more
Max. Pressure?  LOW LOW LOW HIGH
Sample must be at atmospheric pressure.
Typical: 20 psig max.
Sample must be at atmospheric pressure.
3,000 psig with standard flow cell.
Max. Temperature?  HIGH LOW LOW HIGH
Significant error due to temperature sensitivity; sample temperature cannot exceed 50-60 °C.
150 °C with standard flow cell. Software performs temperature compensation.
Moving Parts?  YES NO YES NO
Users report frequent jamming of tape drive.
Solid state instrument.
Consumable Costs?  HIGH HIGH HIGH LOW
Each paper tape reel lasts 1 month and must be manually replaced; humidifier solution (e.g. acetic acid solution)
Copper nanoparticle scrubber replaced each year. High process fluid consumption.
Carrier gas, separation columns, and detectors.
Only requires zeroing fluid (e.g. nitrogen). Xenon light source has 5 year MTBF.
Maintenance?  HIGH LOW HIGH LOW
New tape reel needed each month; frequent tape drive jams; manual dilutions for overload.
Optics require cleaning.
Famously expensive to operate and maintain.
Optics require cleaning once per month -- a one-minute procedure.
Specifications found in product literature from mainstream manufacturers.


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