Street Address: 16 Floor, Building #3, Zhongke Mansion, Gaoxin South 1st Rd, Hi-Tech Park, Nanshan
City: Shenzhen
Province: Guangdong
Country/Region: China
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DESCRIPTION The sensor element consists of a silicon chip with a thin membrane approximately 1mm2 in size of a material with extremely good electrical and thermal insulating properties. On the membrane are two thin film resistors (Rm1, Rm2) which are both used for heating the membrane and for measurement of membrane temperature Tm. The resistors are passivated to protect them from the effects of the gas. The membrane is completely covered by a second small silicon chip with a rectangular cavity etched in. The hollow space thus formed above the membrane is the thermal conductivity section. The gas comes to the measuring section through a small lateral opening in the membrane cover by diffusion only, and not by flow. The sensor chip and its cover are attached to a silicon support which also permits gas exchange to the lower side of the membrane. The sensor is electrically connected to an eight pin base by gold wire bonding. Due to the thermal conductivity l of the gas surrounding the membrane, thermal energy is dissipated from the membrane held at higher temperature Tm. Measured is the signal needed in a temperature stabilization circuit to keep the excess temperature of the membrane DT constant. On the solid part of the chip are two more resistors (Rt1, Rt2) to measure and compensate for the effect of the ambient temperatur. FEATURES