Program temperature drop, also known as programmed freezing apparatus, embryo freezing device, through the microcomputer control temperature drop is the key equipment to realize deep low temperature preservation of biological materials, according to the principle of cooling and control, it can be divided into two categories: liquid nitrogen injection program temperature drop and elevating programmable freezing apparatus.
they are source in liquid nitrogen for cooling.
Liquid nitrogen injection temperature drop is developed in the late 1970 s to succeed.
Mainly by the cooling chamber, solenoid valve, fan at low temperature, temperature sensor, amplifier circuit, microprocessor and liquid nitrogen container.
the cooling process is carried out by computer according to the preset program, can carry out different cooling rate in different temperature range.
Nitrogen by liquid nitrogen bottle through a pipeline to nitrogen gas entrance, electromagnetic valve regulating nitrogen flow at low temperature.
The jet temperature drop temperature range has reached 60 ~ + -
180 ℃, the cooling speed of -
0.
01 ~ -
60 ℃ / min, a speed of 0.
01 ~ 10 ℃ / min, temperature control accuracy reached 0.
01℃/min。
liquid nitrogen injection temperature drop is suitable for large bulk samples to chill, advantage is that the temperature control precision, interference by the external environment is small, but the price is expensive, liquid nitrogen consumption, if there is a small amount of water in liquid nitrogen can cause pipeline plugging and electromagnetic valve failure at low temperature.
elevating program-controlled frozen by liquid nitrogen container, step machine, microcomputer control system, and a recorder.
It is the use of liquid nitrogen in natural evaporation in the dewar temperature field which is formed by the bottleneck department (
0 ~ -
196℃）
By stepping machine according to the preset temperature, complex temperature program control biological specimens the rate at which the temperature in the area to move up and down, to control the temperature and cooling rate of the specimen.
Its operating temperature from room temperature to -
Between 196 ℃, the cooling speed
0.
01 ~ -
10℃/min。
Elevating temperature drop is suitable for small sample volume to freeze, the advantage is low cost, less liquid nitrogen consumption, simple operation, but the temperature control precision is better than injection temperature drop.
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