Do I need to clean the sensor often to keep it working normally·?

This depends on the using times. After a period of using, we should clean the sensor mainly the latent smutch from fingers. Please do not use paper or any organ solvents like alcohol or gas.
Recommended clean method: Use one-sided adhesive tape to stick on the sensor and then remove the tape. After a long time of using, the sensor will be dirty and obscure due to the accumulation of the latent salinity from finger sweat. Please use soft cloth with glass cleanser. Please do not pour glass cleanser to the sensor directly or dip the sensor in any liquid.