The digital density monitoring unit is used as the measuring element which is directly installed in the switchgear. The data is processed by the internal digital analog and the digital signal is directly output and sent to IED. The digital density monitoring unit uses electronic pressure sensor and temperature sensor to measure the pressure and temperature of gas, then the gas scalar pressure is calculated by numerical operation, P20 value .
Micro water sensor using resistance and capacitance method, the structure of the micro water sensor is a high purity aluminum rod, the surface oxidized into a layer of aluminum oxide thin film, and it is coated with an reticular gold film with porous structure. The capacitance is formed between the gold film and the aluminum rod, due to the water absorption characteristics of the aluminum oxide film, the capacitance value changes with the moisture content of the sample gas, and the humidity of oxygen can be obtained by measuring the capacitance value.