H2S Analyzer, Hydrogen Sulfide Analyzer, with Classic Sample Conditioning System, measuring H2S concentration

H2S Analyzer

The OMA H2S Analyzer measures real-time H2S concentration in liquid or gas process by monitoring the UV-Vis absorbance in a continuously drawn sample. The OMA H2S Analyzer can analyze hydrogen sulfide in natural gas, crude oil, water, biogas and landfill gas, feed forward, lean/rich amine, stripped sour water, wastewater, syngas, flare gas, flue gas, hydrogen recycle gas, scrubber outlet gas, LPG and more.

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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Applications: H2S Analyzer

With thousands of units shipped since 1994, the OMA H2S Analyzer has been deployed for a wide range of applications across various industries:

Model: OMA H2S in Natural Gas Analyzer

Raw natural gas contains hydrogen suflide, the level of which varies by field. Due to its toxicity, flammability, and corrosivity, H2S is an extremely important component to control at all stages of natural gas handling, from wellhead to the customer. The destructive effects of H2S on equipment and pipelines along with the constant threat to personnel safety justify major investment in H2S measurement technology.

The OMA H2S Analyzer is a highly field-proven solution for fast-response H2S measurement in several natural gas applications. Due to excellent accuracy and dynamic range, the OMA is the analyzer of choice both for high-level and low-level H2S ranges.

Model: OMA H2S in Crude Oil Analyzer

Crude oil with low sulfur content (“sweet crude”) is coveted because it is more easily processed into usable gasoline. By contrast, sour crude contains a significant H2S concentration and requires more expensive processing. Online H2S analysis is required to determine how much processing a specific feed of crude oil will require and to differentiate different crudes by their commercial value.

The composition of oil presents significant challenges to direct optical analysis. These challenges include aromatic hydrocarbons and/or phenols which absorb heavily in the UV range and act as spectroscopic interferents, particulates which scatter light, and the opacity of heavier crudes (too dark to transmit a light signal and will not allow optical analysis).

The OMA system uses a ‘headspace’ sample conditioning system to circumvent the opacity of crude oil and continuously measure H2S concentration in the stream with proven reliability. The operating principle of the system is Henry’s Law: part of the liquid sample is evaporated into ‘headspace gas’— a vapor-phase sample that is totally representative of the liquid composition and can be analyzed very easily using UV spectroscopy.

Model: OMA Feed Gas (Acid Gas) H2S Analyzer

While tail gas analysis measures the H2S:SO2 ratio after the furnace to calculate air demand correction, a feed forward analysis system measures the H2S concentration in the acid feed gas before the furnace to preemptively adjust air demand based on the real-time feed gas H2S level. While tail gas analysis provides the most accurate air demand calculation, this measurement occurs after the furnace. Feed forward analysis allows for air demand control with no process lag by immediately detecting sudden changes in acid feed gas composition and preventing any losses in SRU efficiency.

The OMA system continuously measures 0-100% H2S concentration in the acid feed gas to provide real-time feed forward control. This system provides the perfect complement to the TLG-837 Tail Gas Analyzer for total SRU air control.

Due to the high levels of H2S monitored, an extremely high attention to the safety aspects of this system was incorporated in the design.

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)

Models: H2S Analyzer

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.



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


  • Carry from site to site
  • Rugged suitcase enclosure


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

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.

Sampling: H2S Analyzer

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.

Specifications: H2S Analyzer

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)
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, PESO, JPN
Please inquire with your sales representative for additional certifications (CSA, FM etc.).
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