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Gas Analysis Probe (GAP)

Designed for monitoring of oxygen content within flue or stack gases, the GAP has relays, analog and modbus outputs along with pressure and temperature compensation making it a complete analyzer for combustion optimization and burner/boiler trim applications.

A compact zirconium-oxide analyzer to efficiently monitor excess air in combustion processes. The probe is manufactured from 316 stainless steel and can handle sample temperatures up to 700°C with an insertion length of 435mm (17.126″). The sample is extracted to the sensor chamber and returned to the flue via the Pitot effect, so there is no need for instrument air. The analyzer operates without the need for an air reference.

Designed with ease of maintenance in mind. The GAP’s user replaceable sensor can be cleaned or replaced in seconds.


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Part Numbering Guide


Electrical Input / Output
Supply voltage 24VDC, ±10% LPS
Supply current 700mA max. at 24Vdc
Digital output RS485 MODBUS RTU
Analogue output Single or Dual 4—20mA
Output ranges
    Oxygen 0-25% O2 (Rangeable)
    Gas Temperature -50 to +700°C (-58 to+1292°F)
    Pressure 750 – 1260mbar absolute
Relays (SPST, N/O as std.) 1 x system alarm (SPST)
1 x user configurable O2 set point alarm
Display 16 character, 2-line, backlit
Mechanical Specifications
Time to first reading 60 seconds
Stabilisation time to stated accurate 10 minutes
    Head 1.6kg (3.5lbs)
    Probe 3.9kg (8.6lbs)
Wetted materials Stainless steel, Macor®, PTFE, aluminium, platinum, aluminium oxide, zirconium dioxide
Process connection 2” 150lbs ANSI flange
Ingress protection IP65
Housing material Painted aluminium
Cable gland SKINTOP MS-SC-M M20x1.5


Measurement technology Zirconium Oxide (ZrO2)
Gas Oxygen
Measurement range 0.1—25%
Output resolution 0.01 mA or 0.01% O2
Accuracy (0.1-25%)
Response time (T90)
Sample Flow Effect ±0.5% of full scale
Sample gas temperature +700°C (1292°F)
Temperature measurement Pt100
Operating Conditions
Ambient temperature -20 to +55°C (-4 to +131°F)
Ambient relative humidity 0-95% RH
Gas composition Combustion gas from natural gas, coal, biogas or oil
Sample gas temperature +700°C (1292°F)
compensated pressure 260—1260mbar Absolute


Flange profile to match ANSI Class 150 lb.
Nominal pipe size 2″
External diameter 152.40 (6.000”)
PCD 120.65 (4.750”)
Flange thickness 19.05 (0.750”)
No. of holes 4
Bolt hole diameter 19.05 (0.750”)
NOTE: The flange is NOT pressure retaining.


  • The GAP provides customers with a single gas flue or ventilation monitoring control system
  • Barometric pressure and temperature sensors included
  • RS485 MODBUS RTU as standard
  • User configurable relay and analog outputs
  • Easy to swap sensor module, no special tools
  • Calibrate in fresh air or cal gas via external calibration port
  • Various probe lengths available


  • Combustion control of burners fueled by natural gas, light oil, diesel, coal and biomass
  • Excess air analysis
  • Boiler trim control
  • Incineration furnaces
  • Power generation
  • Combined cycle gas turbines (CCGT)
  • Ceramic furnace monitoring
  • This field is for validation purposes and should be left unchanged.