Increase of catalytic sensors stability

Silicon MEMS Thermocatalytic Gas Sensor in Miniature Surface Mounted Device Form

“…The typical sensor response with "fresh" catalyst is presented in Figure 4. This was followed by tests for long-term stability, since it is known that in order to stabilize the properties of a catalytic material, a few weeks of its annealing in methane containing ambient is required [18].…”

“…Modern research is focusing on the miniaturization of the sensors [14,15], reducing the energy consumption [16] and increasing the stability of the catalysts to provide stable sensitivity in long term [17]. As the thermocatalytic sensor technology has been used in its current form since the beginning of the 1950s [18], they are now going to be outdated in view of their energy consumption and the related encapsulation requirements as well as the latest technology improvements. The small size and the consequent minimized power consumption of the sensor are essential for wearable alarming devices, especially when the sensor is operated in a harsh, explosive environment.…”

“…Currently, the power consumption of the best bead type thermocatalytic sensor is at least 140 mW for the two sensors, using 10 µ Pt wires covered by 2 µ SiO 2 glass [19], but the typical bead type of the sensors on the market are made from non-covered 20 µ Pt wire [20] and have 190 mW power consumption at 450 • C constant working temperature. Three ways are seen to reduce the power consumption: improving the technology of the microhotplate platforms to get a uniform temperature profile at the lowest temperature needed for the catalysis and achieve it by minimum power dissipation [21][22][23][24], increasing the catalyst activity and stability of the gas sensing material [15,18], or by using non stationary methods for measuring flammable gas concentrations in pulsed temperature mode [21,25]. The present work describes the progress in these fields, aiming at the development of a battery-operated wearable methane sensor by introducing a reduced power dissipation hotplate and an SMD compatible ceramic encapsulation technique.…”

Method for Determining the Concentration of Unknown Combustible Gas

“…A core diameter is 10 µm and insulation thickness is 2 µm. A principle of operation of such sensors based on flameless burning (oxidation) of combustible gas on the catalytic active surface and measuring the amount of released heat, which is proportional to the concentration of combustible gas [4]. Figure 1b shows the scheme of test stand.…”

“…A correction factor K = S1/S2, characterizing the rate of sensitivity decrease on the analyzed gas during the temperature increase, is calculated. 4 Corrected signal is calculated using empiric formula:…”