Constant pressure control device of helium of vacuum system

The utility model provides a constant pressure control device of helium of a vacuum system. The constant pressure control device of helium of a vacuum system provided by the utility model is characterized in that a vacuum gauge is used for measuring the pressure signal of helium within the vacuum system, the pressure signal is compared with the pre-determined value to generate a feedback signal, the heating power of a filtering type helium gas microleak valve (hereinafter referred to helium leak, see the patent CN1479031A) is regulated according to the feedback signal, and therefore the pressure of helium of the vacuum system is finally reached to the pre-determined value. The device and the method provided by the utility model have the following advantages: the pressure signal is directly fed back by using a vacuum gauge, the heating power of helium leak heating wire is controlled by means of the feedback signal, the permeability of helium is regulated, the purpose for directly controlling the pressure of the helium which is injected into the vacuum system is realized, the influences of the environmental temperature, the pumping speed of vacuum pump and the pressure difference change for the helium of two sides of the helium leak are prevented; the control purpose of heating power of helium leak, namely the permeability of helium is realized by the control device by means of pulse width modulation, and the control sensitivity to the pressure of the helium which is injected into the vacuum system is high.