Thermal Conductivity Analyser

8866 is an analyzer for harsh environment that allows very accurate and stable in line analysis of a gas in a binary (or almost binary) mixture, taking advantage of its own specific thermal conductivity, respect to the background gas.

 The weatherproof and explosion proof 8866 is designed for field installation in the most severe conditions, minimizing the sample conditioning requirements.

Measureable Gas

Hydrogen [H2]

Helium [He]

Air [Air]

Sulfur Dioxide [SO2]

Acetylene [C2H2]         

Argon [Ar]

Nitrogen [N2]

Special 3-Ranges Calibration for Hydrogen Cooled Generators [TR]



Carbon Dioxide [CO2]

Nitrous Oxide [N2O]

Methane [CH4]

Main Features

Extreme Roughness

  • No inner moving parts
  • Wet parts in AISI316 and glass
  • Resistant to the most severe industrial environments


High Performances

  • Sensing unit temperature controlled
  • Insensitive to ambient temperature variations
  • Installation position and vibration don’t alter the accuracy and stability of the measure
  • Available as 4-20 mA transmitter or combined with a powerful microprocessor-based control unit


Easy Maintenance

  • Modular construction
  • Fast access to the inner PCB just unscrewing the housing cap
  • Possibility to remove the entire sensing unit from the housing just by unscrewing 2 screws and leaving her housing connected to the sampling system.


European Compliance

  • Low Voltage Directive 2014/35/EU
  • EMC Directive 2014/30/EU
  • Directive ATEX 2014/34/EU (optional)



ATEX certification for Zone 1 / Zone 21 with protection mode:

 II 2 G D     Ex db IIC T6 Gb

                  Ex tb IIIC T85°C Db


 ATEX Certificate Number CESI 03 ATEX 130


Accuracy± 1% of span (output signal). Further improvable with
autocalibration and four port version with reference gas
Repeatability± 0.3% of span (short term).
Reproducibility24 hours: ± 1% of span.
Linearitybetter than ± 0.5% of full scale
Response TimeH2: Initial < 1 sec.; 60%: 13 sec.; 90%: 23 sec.; 99%: 40 sec.
CO2: Initial < 2 sec.; 60%: 24 sec.; 90%: 45 sec.; 99%: 80
sec. (with max. 2000 cc/min. flow rate)
DriftZero: max. ± 1% of span per week
Span: max ± 1% of span per week (without autocalibration).
Ambient Temp. Influencedepend on range; typically < 1% of FS over the entire temperature range (-10°C ÷ +50°C)
Pressure Influencenone for pressure variations between 0.1 and 10 bars (a)
Flow Rate Influenceless than 0.5% of span over flow range of 250 to 1000 cc/min.
Line Voltage Influencemax. 0.02% of span, for each 1% change of power voltage.
Sample RequirementsFlow Rate: 250 ÷ 1000 cc/min.
Pressure: 3000 Pa minimum (with filter and flow meter).
RangeRefer to ordering information
Outputnon-normalized output current that functions as input of the selected ADEV control unit
Relative Humidity90% maximum.
Operation Temperature-10 ÷ +50°C (14 to 122 °F).
Temperature controlledat 50°C
Storage Temperature+70°C (158 °F) max.
Power Requirements24 ÷ 30 Vdc, 45 VA from dedicated power supplier.
Pneumatic Connections¼” or 6 mm OD tubing (compression fittings supplied)
Wiring ConnectionsGeneral purpose: 2 openings for G 3/8" (PG 13 cable grip).
Ex-Proof: 2 openings for GK 1/2" (cable grip or conduit).



Heat treatments

Iron and steel industry

Galvanizing furnaces

Copper melting furnaces

Nuclear plants and electric power industry

Hydrogen cooled generators

Measure of H2 in hydrocarbons in petroleum industry


Hydrogen generators

Gas production industry (purity monitoring of H2, Ar, N2, He, CO2, N2O)

Synthesis gas & Fertilizers


Sampling System

The 8866 needs an external sampling system able to deliver an almost clean sample gas to the analyser at the proper temperature, pressure and flow rate.

ADEV has a wide experience in process and can provide the 8863 analyser combined with a sample and condition system designed for the specific application requirements. Contact ADEV for details.

Measuring Principle


The Cell Block assembly is made of stainless steel construction with two identical internal cells: the measuring cell and the reference cell. A highly stable thermistor is mounted in each cell.

 These matched thermistors form the active arms of a bridge circuit: the unbalanced current of the bridge provides the means of measuring the relative ability of the sample and reference gases to conduct heat away from their respective thermistors to the cell wall, which is held at a constant temperature.

 The standard two port version is used for zero-based ranges and has reference side sealed (air-filled). For suppressed ranges from 95%, the use of the four port version, with specific flowing reference gas, increase the accuracy to the maximum level.