The rapid development of conductor technology has led to the use of VVVF voltage regulation and frequency 

modulation traction inverters and CVCF auxiliary inverters in the traction control and auxiliary power supply 

systems of modern and advanced urban subways and light rail vehicles. Like mainline AC-DC-AC transmission 

vehicles, current sensors and voltage sensors are also widely used in the DC and AC circuits of the aforementioned 

systems to achieve closed-loop control of the entire system. In the air conditioning system of urban rail transit 

vehicles, sensors and electronic temperature controllers are often used in combination for temperature control. 

Temperature controllers often use electronic regulators and sensors for temperature detection, usually using 

thermocouples or thermistors as sensors. The temperature and displacement sensors developed by Longlv 

Electronic Needle for its characteristics are widely trusted by rail transit units due to their stable performance 

and precise monitoring