The electrical characteristics of the discharge path of open gas discharge tube mainly depend on the environmental parameters, so the stability of the work can not be guaranteed. In order to improve the working stability of the gas discharge tube, the gas discharge tube mostly adopts the metallized ceramic insulator and electrode welding technology, so as to ensure the sealed shell and the air tightness of the discharge gap, which creates conditions for the selection of gas types and pressure in the discharge tube. The gas discharge tube is generally charged with neon or hydrogen gas.
Various electrical characteristics of the gas discharge tube, such as DC breakdown voltage, impact breakdown voltage, impact current resistance, power frequency current resistance and service life, can be adjusted and optimized according to the requirements of the system. This adjustment is usually achieved by changing the gas type, pressure, electrode coating material composition and electrode distance in the discharge tube.
There are two types of gas discharge tube: two electrode discharge tube and three electrode discharge tube. Some gas discharge tubes have electrode leads, while others do not.
In terms of structure, the gas discharge tube can be regarded as a symmetrical switch with a small capacitance. Under normal working conditions, it is turned off and its inter-electrode resistance reaches more than megohm level. When the surge voltage exceeds the voltage strength of the circuit system, the gas discharge tube is broken down and arc discharge occurs. Due to the low voltage of arc light, only tens of volts, which can limit the further rise of surge voltage in a short time. The gas discharge tube uses the above principle to limit the surge voltage and protect the circuit from overvoltage.
As the overvoltage decreases, the current passing through the gas discharge tube also decreases. When the current falls below the minimum current value required to maintain the arc state, the arc discharge stops and the glow of the discharge tube is extinguished.
Gas discharge tube is mainly used to protect the communication system, traffic signal system, computer data system and all kinds of electronic equipment external cables, electronic instruments safe operation. Gas discharge tube is also the circuit protection element against lightning and instantaneous overvoltage.
Gas discharge tube has the characteristics of large current carrying capacity, fast response time, small capacitance, small volume, low cost, stable performance and long life. The disadvantage is that the ignition voltage is high, can not restore the cut-off state under DC voltage, can not be used to protect the low voltage circuit, each time after the transient voltage action, the performance will decline.