Model 931 Single Gas H2S Analyzer (with H2 and HC Options)

The Model 931 uses a sophisticated UV-VIS photometer to measure any single UV-absorbing gas species for process monitoring and control.


The Model 931 uses a sophisticated UV-VIS photometer to measure any single UV-absorbing gas species for process monitoring and control. Additional IR and thermal conductivity sensors capable of detecting non-UV absorbing species, such as CO2 and H2 can be incorporated into the design. The 931 is provided as an explosion-proof package making it suitable for most chemical and petrochemical applications.

This analyzer uses AMETEK’s proprietary high-resolution UV-VIS technology which is completely free from water or hydrocarbon interference, maximizing measurement accuracy. A very flexible design, the 931 can be optionally equipped with additional sensors to add the capability to monitor CO2 and H2.

The Model 931 analyzer utilizes industrial electronics to provide concentration calculations, data processing, temperature control, calibration and sophisticated self-diagnostics. No matter what your need is, this rugged analyzer is solid proof of AMETEK’s worldwide reputation for durability and reliable performance.


  • Class I, Division 1, or ATEX II 2 G Hazardous Area Rating
  • Direct measurement
  • Provision to return sample to process (with heated acid gas probe option)
  • Minimal sample conditioning
  • Dual-beam, dual-wavelength design
  • Optional detectors available (thermal conductivity-hydrogen and IR-hydrocarbon


Hydrogenation Reactions (hydrogen sulfide, hydrogen)
Feed gas analysis
Reaction rate monitoring
Impurity detection
Quality assurance monitoring


Methodology Dual wavelength, high resolution, nondispersive UV/VIS
Full Scale Ranges ppm and % vol are standard, other ranges are available
Standard Range
H2S 0 to 4,000 ppm min. to 0 to 100% max.
Other components and ranges are available upon request. Other components may include NH3, COS, CS2 and SO2
Accuracy Standard range (UV): ±1% of full scale
Optional (TCD) H2 sensor for TGTU applications: ±2% of full scale
Optional (IR) sensor for THC, CO2: application specific, consult factory
Repeatability Better than ±0.5% of full scale
Linearity Better than ±1% of full scale for H2S
Zero Drift Better than ±2% of full scale, with auto zero disabled over 24-hour period
Speed of Response Typically less than 30s to T90 (excluding sample system)
Number of Gases one
Zero Gas Nitrogen or instrument air
Maximum Sample Cell Pressure: 6.9 barg (100 psig)
Maximum Sample Gas Temperature: 165 ºC (329 ºF)
Typical Sample Flow 2.5 L/min (5 SCFH)
Sample Transport Application dependant (options include Heated Acid Gas probe)
Outputs Up to 4 isolated 4-to-20 mA, loop or selfpowered, 30 VDC Max; 4 non-isolated 1 to 5 VDC;
5 independent sets of SPDT, Form C, potential free alarm relay contacts, 2 A at 240 VAC
Digital Communication RS485 Modbus port; RS232 / RS485 service port
Utility Requirements 120 VAC (104 to 132 VAC), 47 to 63 Hz, <3A
240 VAC (207 to 264 VAC), 47 to 63 Hz, <2A
Power Consumption 500 W max. (with heated probe and cell)
Ambient Temperature 0 to 50˚C (32 to 122˚F)
Physical Dimensions 1185 x 780 x 254 mm (46.65 x 30.7 x 9.97 in.)
Weight Approximately 145 kg (320 lbs)


Model 931 Single-Gas Analyzer
Heated Acid Gas (HAG) Sampling Probe