Golden Plated Lift Hold
Golden plated Lift Hold Gas sensor At present, there are two kinds of domestic gas sensors. One is a direct heating type, and the heating wire and the measuring electrode are sintered together in the metal oxide semiconductor die; the other is a side heating type, the gas sensing element is...
Golden plated Lift Hold
At present, there are two kinds of domestic gas sensors. One is a direct heating type, and the heating wire and the measuring electrode are sintered together in the metal oxide semiconductor die; the other is a side heating type, the gas sensing element is based on a ceramic tube, the tube is covered with a heating wire, and the tube has an outer side. Two measuring poles, the metal oxide gas sensing material between the measuring poles, is sintered at high temperature.
Taking the SnO2 gas sensor as an example, it is composed of a crystal of 0.1--10 um, which works as an N-type semiconductor. Under normal conditions, it is in a state of oxygen ion vacancy. When a combustible gas molecule having a small dissociation energy and easily losing electrons is encountered, electrons migrate from the gas molecules to the semiconductor, and the carrier concentration of the semiconductor increases, and thus the electrical conductivity increases. For a P-type semiconductor, its crystal lattice is in a cation-deficient state, and its conductivity is reduced when a flammable gas is encountered.
The temperature characteristics of the gas-sensitive resistor are shown in Figure 2.4.1. In the figure, the ordinate is the sensitivity, that is, the value of the voltage obtained on the load due to the change in conductivity. It can be seen from the curve that SnO2 can adsorb gas at room temperature, but its conductivity does not change much. However, when the temperature is increased, the conductivity changes greatly, so the gas sensor needs to be heated during use.
In addition, a small amount of lead, platinum, gold, silver and other elements and some metal salt catalysts can be added to the material of the gas sensor to obtain sensitivity at low temperatures and to enhance selectivity to gas species.
According to the heating method, the gas-sensitive resistor can be divided into two types: direct heating type and side heating type. The direct heating type consumes a large amount of power and has poor stability, so the application is gradually reduced. The side-heating performance is stable, the power consumption is small, and the structure is often explosion-proof with a double-layered stainless steel wire mesh, so it is safe and reliable, and its application surface is wide.