Model 920 Hot/Wet Multi Gas Analyzer

The AMETEK Western Research Model 920 is specifically configured for monitoring the stack emissions of multiple pollutants on a concentration basis


The AMETEK Western Research Model 920 is specifically configured for monitoring the stack emissions of multiple pollutants on a concentration basis. It measures as many as five pollutants at stack conditions. With the addition of an optional zirconium oxide sensor, the Model 920 is capable of monitoring oxygen.

The Model 920 is a very robust and reliable analyzer. Its UV-based measurements do not suffer from H2O and CO2 interference. They can also have a wide dynamic range for some measurements. This greatly simplifies sample handling and sample integrity as there is no need for sample drying. As a fully extractive, heated wet basis analyzer, the 920’s sample system components are simply heated above the dew point of the sample gas. This results in a simpler and more accurate calculation of gas concentrations, requiring no corrections for condensed and dissolved components.

The Model 920 performs all necessary sample gas and calibration gas flow management, and probe and sample line temperature control. The Model 920 is a full function Continuous Emissions Monitoring System (CEM) which requires the addition of only a sample probe and sample line to be fully operational. Housing options for the analyzer include a cabinet or walk in shelter built to your specifications.


  • Hot/wet analysis prevents errors associated with water vapor, and absorption losses in driers
  • Able to measure up to five of the following species: SO2, NO, NO2, H2S, NH3 or a number of other chemicals
  • Multi-range SO2 analysis possible
  • H2O or CO2 interference
  • Automated zero and span gas calibration
  • Serial communication with plant DCS


Methodology: Multiple wavelength, high resolution, non-dispersive UV
Species Measured Minimum Full Scale (see Note) Maximum Full Scale
SO2 250 ppm 100%
NO 300 ppm 100%
NO2 300 ppm 100%
NOx 300 ppm 100%
H2S 500 ppm 100%
NH3 125 ppm 100%
Cl2 500 ppm 100%
COS 1000 ppm 100%
CS2 2500 ppm 100%
Optional O2 Integral Zirconium Oxide
Accuracy +/- 1.0% full scale of standard ranges
+/- 2.0% full scale of standard ranges for H2S+NH3 application
Repeatability Better than 0.5% full scale
Linearity Better than 1% full scale
Response Time Typically less than 30s to T90 (excludes sample system)
Number of Gases Up to 5 simultaneously (refer to AMETEK for possible combinations)
Sample Transport Air aspiration
Typical Sample Flow 3 to 5 L/min (0.1 to 0.2 CFM)
Sample Gas Temperature Ambient to 150°C (302°F)
Temperature Control Independent control of three zones (oven, sample line, probe)
Pressure and Temperature Compensation Standard
Ambient Temperature2 5° to 50°C (41° to 122°F)
Instrument Air Minimum 413.6 KPa (60 psig), 120 L/min (4.24 CFM), instrument quality air
Power 120 VAC ±10%, 47-63 Hz or 220 VAC ±10%, 47-63 Hz, 600 W for analyzer only
Analog 4 x 4-to-20 mA self-powered
Digital One RS232 port for service diagnostics
One RS422 with Modbus protocol
Relays 3 independent sets of SPDT relays alarm conditions
Physical Dimensions 1553.6 x 1117.6 x 306 mm (61.17 x 44 x 12 in.)
Weight Estimated minimum 160 kg (350 lbs)
Approvals and Certifications NEC/CEC Class I, Division 2, Groups C & D
Russian Ex Proof Certification; 1ExpydIIBT3
Russian Gosstandard Pattern Approval
Complies with all relevant European Directives
1. Accuracy may vary on some applications where multispecies measurement is required.
2. Temperature drift is approximately 1 ppm/°C for the species listed. To achieve maximum accuracy and stability, you can either install the analyzer in a temperature-controlled environment or zero the analyzer more frequently.


Model 920 Multi-Gas Analyzer
Heated Acid Gas (HAG) Sampling Probe