FTTC 1100 thermal conductivity analyser with Fourier transformation

For the constant regulation of Density and Calorific value in gas mixing stations, AMS has developed the Thermal Conductivity Analyser FTTC 1100 with Fourier transformation of the sensor signal. For this application fast responses of the thermal conductivity sensor are required, since the changing’s of density and calorific value occurs fast and within narrow boundaries. A typical application for this analyser is the measuring of methane, carbon dioxide and nitrogen in Bio-Gas and Natural gas.

The conventional measurement of the thermal conductivity of gases is limited to binary gases. However, the thermal conductivity measurement with Fourier-Transformation allows the simultaneous measurement of three and four gas components. Only with the invention of miniaturized thermal conductivity sensors, with an extremely low thermal mass, this technology could be realized. It has become feasible to use the physical effect of the varying thermal conductivity of gases with the change of the temperature.

Due to the modulation of the membrane temperature of the sensor, the measuring signals of a gas mixture shows periodic changes which can be displayed as Fourier-Coefficients. The first step in setting up an application is the definition of a calibration matrix which covers the range of the expected gas concentrations. In a mixture of three gas components this can be visualised in a two- dimensional diagram, as the third component is the supplement to 100 %. Calibration thereby means, to establish with the help of known gas mixtures a correlation matrix between a set of concentration values and a set of Fourier coefficients. The temperature of the sensor block, the average membrane temperature, the amplitude of the temperature modulation and the modulation frequency has to be defined and optimized for each and every application.

The thermal conductivity analyser FTTC 1100 is usually installed in a wall mounting housing IP 65. The micro-processor controlled electronics is seperated from the gas analytics. Calibration and service are controlled via the keyboard in the analyser menu. Integrated automation components such as the time-controlled calibration allow the remote operation of the Thermal conductivity Analyser FTTC 1100 from the control room.

Technische Daten

AnalyserFT-TC 1100 für Biogas / Erdgas
Measuring components / ranges
Methane (CH4) Carbondioxide (CO2) Nitrogen (N2)
The measuring ranges have to be selected specifically for an application
40...90 Vol%
5...50 Vol%
0...30 Vol%
Analogue output (Option)each measuring component 1* 4 ... 20 mA, galvanically sperated
Repoducability< 2% of the measured value
Long term drift< 0,5 Vol. % according to application
T90 time< 20 seconds
Digital communicationInterface RS 232 / RS 485
Ambient temperature+5 °C to +40 °C
Gas temperaturemax. +40 °C
6 mm Klemmringverschraubung
6 mm Klemmringverschraubung
Gas flowMeasuring gas 20 … 50 Nl/h
Gas pressure (inpet)min. 20 mbar (g)
max. 500 mbar (g)
Power supplyWide range 90...240 V AC / 24 V DC
Protection class / housing /IP65
Dimensions600 x 380 x 210 mm (hxwxd)
Weight10 kg, depending on protection class
OptionsSuitable for operation in Ex-Zone 2, flame barriers
Version: AMS FTTC1100 T V02-2014