MessKonzept FTC300, Руководство по эксплуатации

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Gas Out
130
˚
C
60
˚
C
Gas In
Figure 2.1: Schematic drawing of thermal conductivity measurement. The sensor is comprised in the
stainless steel block which is kept at a constant temperature.
The FTC300 contains a thermal conductivity sensor to analyze the quantitative composition of gas
mixtures. The measurement is based on the heat transfer between a heat source and a heat sink.
The measuring gas is led through a stainless steel block that is kept at a constant temperature
of 63
◦
C (for most applications). The block temperature is stabilized using a control loop - it serves as
a heat sink of constant temperature. A micro mechanically manufactured membrane with a thin-film
resistor serves as heat source. A control loop stabilizes the membrane temperature at 135
◦
C (for
most applications).
Above and below the membrane two small cavities are etched into the silicon. These cavites are filled
with measuring gas by diffusion. The surfaces opposite to the membrane are thermally connected
with the heat sink. Through maintaining a constant temperature gradient between the two opposite
surfaces, the heat flow is dependant of the gas mixture’s thermal conductivity alone. Hence the
voltage needed to keep the membrane temperature constant is a reliable measure for the thermal
conductivity of the mixture and can be used further to determine the gas mixture’s composition.
File name:
FTC300 Manual 1.09KD140704CWI1V05.pdf