The use of microelectronic (MEMS) sensors in process control systems – the main line of development of modern means of automation. Introduction of smart sensors is driven largely by low cost (thanks to the use of high technologies in their production). However, the situation in the market of gas flow sensors, thermal conductivity and the like, using in its structure, precision temperature control system heating gas to be measured, it remains at 20 30 years ago. Most common in hot-wire anemometer acquired three-element modules consisting of a heater and two thermometers based on measuring the temperature difference between the gas before and after heating

The advantage of this module is the clear physical principle of operation and use as active elements in the traditional wires, and the latest designs – thin-film thermistors. Their common drawback is the low resistance of thermistors, and consequently overheating measuring current, which reduces the accuracy of the instrument. The desire to minimize the size of the module, its thermal inertia and energy consumption requires placing the module inside the measured flux, and therefore must take into account the gas-dynamic characteristics that affect heat transfer. In particular, the thin-film design is imperfect in gasdynamic regard as a platform. Conditions of flow and heat transfer due to forced convection are dependent on many factors: the geometry of the channel, location relative to the flow core, the angle attack, the presence of turbulence, and others is not measured by the gas temperature and the temperature sensor housing that does not introduce errors only in the steady state..

« »