INM-700 In-Situ NOx/O2 Monitor


HORIBA's INM-700 in-situ gas analyzer is designed to meet the requirements of coal-fired power generation plants for cost-effective, low maintenance NOX monitoring. The analyzer uses a ceramic diffusion filter and Zirconium Oxide sensor directly in the gas stream, which eliminates the need for an extraction process for sample collection, and results in lower maintenance. The INM-700 is ideal for inlet SCR control, NOX measurements, and burner balancing/combustion tuning in boiler plant operations.

The INM-700 has the advantage of lower installation, maintenance, and capital costs, and a faster response time. In addition, for compliance strategies, the ceramic filter allows measurements to be taken near the combustion point of the furnace. This technique utilizes combustion modification techniques such

  • Low NOX burners (LNB)
  • Over-fire air injection (OFA)
  • Gas re-burn systems
  • Boiler tuning
  • Combustion optimization programs


  • SCR control
  • Inlet/outlet NOX measurement
  • Replacement of FGAS shelters
  • Burner balancing/combustion tuning
    • Improved burner efficiencies and reduction of NOX
    • Identifying problem areas in the furnace due to gas stratification linked to specific burner columns.

INM-700 literature


  • A NOX sensor using a new technology for coal fired applications which can improve control of the ammonia injection rate in SCR systems.
  • A practical NOX sensor with a fast response time that can be directly installed in the combustion gas stream.
  • Extremely robust sensors that are long lived and capable of withstanding elevated temperatures.

Manufactured by HORIBA





Zirconium sensor type (Demarcation current)*1

Measurement range

NOX: 0 to 1000ppm
O2: 0 to 25voL%


±1.0% of full scale


±2.0% of full scale/week*2

Response time(T90)

10 sec. or less


±3.0% of full scale

Warm up time

Approx. 5 min.


LED digital display (effective 4 digits) for measuring value
LCD display for parameter setting

Output signal

NOX: DC 4 to 20 mA, maximum permissible load 600 Ω
O2: DC 4 to 20 mA, maximum permissible load 600 Ω

External output

NOX high/low-alarm, O2 high/low-alarm, Power failure alarm, Abnormal


DRY calibration, Automatic (1 hour to 99 days 23 hours configurable), Manual

Calibration gas

O2 zero: Standard gas (NO), O2 span: Cylinder air, NO zero: Cylinder air, NO span: Standard gas (NO)

Sampling probe

Flange: JIS 5K 65A FF, Probe length: 520 mm [20.47 inch], Material: SUS316

Sensor cable length

Max. 50m [164 ft.]

Installation condition

Indoor or outdoor, operational temperature: -10 to 50°C [23 to 122°F], Humidity: 90% RH (non condensing)


AC100V to 240V

Power consumption

Approx. 60VA




Probe unit: approx. 10 kg [Approx. 22lbs]
Controller unit: approx. 20kg [Approx. 44lbs]

Cooling air (Instruments air)*3

Dew point: -20°C [-2°F] or less
Pressure: Approx. 300kPa
350°C to 400°C [662°F to 752°F]: Approx. 70 L/min.[2.47 cfm]
300°C to 350°C [572°F to 662°F]: Approx. 50 L/min.[1.77 cfm]
200°C to 300°C [392°F to 572°F]: Approx. 40 L/min.[1.41 cfm]

Purge air (Instrument air)*4

Temperature: 25°C [77°F ] or less (No dust, mist and Non-condensing moisuture content: 0.6% of less at 0°C [23°F]
Pressure: Approx. 300kPa
Consumption: Approx. 3 L/min.

Sample gas condition*5

Pressure: ±3kPa (constant with no fluctuation)
Velocity: 20m/sec. or less
Temperature: 400°C [752°F] or less
Dust: 20g/m3 or less
O2: 1 to 25 voL%
CO2: 0 to 20 voL%
H2O: 3 to 20 voL%
SO: 1000ppm or less
NH3: 1ppm or less
H2: 500ppm or less

*1 Compared to the actual value, the measured value changes according to the moisture content in the target gas because of wet-basis measurements (effect on the indicated value by partial pressure of water).

*2 First week of operation at ±2.0% of full scale per day. 

*3 No oil, mist and dust. When instruments air cannot be arranged that safisfies these conditions, handle by arranging a small compressor or similar equipment.

*4 Instead of cylinder air, instrument air that is free of oil and mist may be used for calibration and purge air.

*5 Make sure not to include components other than those listed in the sample gas conditions. Speficically, when there are corrosive or poisonous components (such as F, Cl, Si, Pb, Zn, Sh, As) , the sensor may degrade in a short period of time.