Model WDG Insitu Probe

The THERMOX Model WDG Insitu flue gas oxygen probe differs from all other oxygen insitu probes.


The THERMOX Model WDG Insitu flue gas oxygen probe differs from all other oxygen insitu probes. The unique inner/outer probe design facilitates removal of cell, heater and thermocouple assembly through the probe head. Once the inner probe assembly is removed, the outer probe support pipe allows straight run access to insitu filter for cleaning with compressed air. The inner probe assembly also exposes the reference side of the zirconium cell to ambient air eliminating the need for instrument air utilities at the probe mounting location. The combination of component access and reduced utility requirements provides a cost-effective reduced maintenance solution for today and tomorrow’s gas, oil and coal fired boiler operations.


  • There are two control options available for the WDG Insitu flue gas oxygen probe to maximize integration with existing plant or process control system:
    • 2000 Series Microprocessor Control provides 4 line local display, analog outputs, alarms, expanded system diagnostics, auto calibration option.
    • 1200/1210 Series Compact Control provides 2 line local display, one analog output, alarms, general system diagnostics, software supported manual calibration.
  • Completely field serviceable.


Principle of Operation Zirconium Oxide
Output Range From 0-1% to 0-100% oxygen
Accuracy ±1% of measured value or ±0.05% oxygen, whichever is greater
Response 63% of a step change in <20 seconds
Drift <0.1% of cell output per month (<0.005% O2 per month with 2% O2 applied)
Linearity ±1% of output span
Repeatability ±1% of output span
Max. Flue Gas Temp 1250ºF (600ºC). Probe material highly corrosion resistant
Alarm Alarm can be set to oxygen, start of calibration, start of verify, or both
Contact Rating 1 A, 30 V max., noninductive load, AC or DC
Diagnostics Watchdog timer and service alarm (trouble alarm). System test for A/D, RAM, and EEPROM. Twenty-entry event log.
Communications RS-485, RS-232 (IQ links), HART© Option available
Analog Output Isolated linear current output. Select O2, cell temperature, thermocouple mV or cell mV. The output can be 4-20 mA, 0-20 mA, 20-4 mA or 20-0 mA and is fully scalable.  Hold or track during calibration and select degree of damping.  Maximum load 1100 ohms.
Sample Pressure ±10 in. water gauge
Power Requirements 115 VAC, ±10%, 47-63 Hz; 230 VAC, ±10%, 47-63 Hz, 150 VA max.
Enclosure UL Type 4X (NEMA 4X). Optional NEC Class 1, Div 2 version available (for subatmospheric pressure only)
Calibration Oxygen cell lifetime extender. Calibrate or verify calibration. Store last calibration gas run time and process recovery time. Timed automatic calibration with optional Remote Calibration Unit.
Calibration Gas Requirements Use calibration gases at 10 psig, 1 to 2 schf (0.70 kg/cm2, 0.47 to 0.94 L/min)


WDG-INSITU flue gas oxygen analyzer