Liquid level monitor tracks LN₂ liquid level and temperature continuously and reliably inside the tank and informs users to refill LN₂. It is suitable for institutes requiring long time cryopreservation. Available in 3 different configurations: A. single-point level alarm through the temperature: with buzzer alarm function available B. single-point level alarm through the temperature; with buzzer alarm function available; with output switch control signal and direct-driven solenoid C. single-point level alarm through the temperature; with buzzer alarm function available; with output switch control signal and direct-driven solenoid