PCR machine is also called gene amplification instrument or thermal cycler. It is developed according to polymerase chain reaction technology. According to the purpose of DNA amplification and detection standards, PCR machines can be divided into ordinary PCR machine, gradient PCR machine, real-time fluorescence quantitative PCR machine and so on.

The function of the thermal cover of the PCR system is not to prevent evaporation, but to prevent the evaporated water vapor from condensing on the tube cover. The thermal cover of the PCR system can be generally divided into four types, namely, non-adjustable thermal cover, adjustable thermal cover, self-adaptive thermal cover and automatic thermal cover.

1. Non-adjustable thermal cover: It refers to the thermal cover that is not suitable for both high and short tubes;

2. Adjustable thermal cover: The height of the thermal cover can be adjusted manually, and it is suitable for all kinds of high and short tubes, but the pressure needs to be felt by oneself, and there may be troubles if the force is too small or too large. Torque-type adjustable thermal cover, that is, the built-in mechanism slips after the thermal cover rotates to a certain torque, so as to ensure a certain thermal cover pressure.

3. Self-adaptive thermal cover: the thermal cover comes with a pre-compressed spring, which is combined with the handle mechanism for opening and closing the thermal cover, so that the thermal cover is automatically compressed when the handle is pressed, and is automatically released when the handle is opened. It can adapt to high and low tubes, so don't worry about the pressure and not loosening the cover.

4. Automatic thermal cover: the thermal cover is pressed and loosened by the motor. It is generally used for a PCR machine that cooperates with laboratory automation, or is called a fully automatic PCR machine.