When low temperature gas molecules collide with high temperature solids, they take heat from the solids. The vacuum gauge that calculates the pressure by the heat taken by the gas molecules is called a heat conduction vacuum gauge. Thermal conductivity vacuum gauges are mainly used in the field of low and medium vacuum. Representative heat transfer vacuum meters include Pirani gauges and thermocouple gauges. The world-famous vacuum company uses platinum wire instead of the traditional filament in the production process of the Pirani vacuum gauge. Greatly improved product stability. The improved stability makes the Pirani vacuum gauge more widely used. With the popularization of vacuum technology, it is widely used in single crystal furnace equipment to meet the basic single crystal silicon production in the photovoltaic industry. It is applied to the energy-saving lamp capillary exhaust station, which solves the problem of the vacuum gauge crash caused by the ignition and high temperature of the spark leak detector. If you look closely at many modern vacuum technology line equipment, you will find this Tamagawa vacuum gauge widget, which is widely used. Vacuum has progressed with the commercial industry and has entered a field that is closely related to everyday life. Resistance vacuum gauge principle The Pirani Pirani gauge is constructed as shown. The inside of the metal cylinder is provided with a thin white gold wire, and the electrodes are connected at both ends. When the current is supplied to the thin platinum wire through the electrode, the thin platinum wire will generate heat, and the gas molecules collide with the thin platinum wire or the heat radiation or the solid heat conduction, and the heat of the platinum wire will be taken away. The heat taken away by the above three methods per unit time is Qg, Qr, Qs, and the following formula is established under equilibrium conditions. Q = I2R = Qg + Qr + Qs (1) Q is the heat released by the thin line per unit time, R is the resistance of the thin wire, and I is the current of the thin wire. When the average free path of the gas is much larger than the diameter of the thin wire, Qg is expressed as heat transfer by free molecules. Qg = αΛπda(T-T0)p (2) As shown, T and T0 are the temperature of the thin wire and the metal cylinder, respectively, P is the gas pressure, and a is the length of the thin wire. The remaining Qs and Qr can be expressed as follows Qs = Sκ(T-T0)/L (3) Qr = πdaσε(T4-T04) (4) (3) is the thermal conduction of the electrode, where S is the cross-sectional area of ​​the thin line, κ is the conductivity of the solid, and L is the length of the electrode. Equation (4) represents thermal radiation, and σ and ε are referred to as constant and solid radiance, respectively. If T and T0 are kept constant, then equations (3) and (4) are constant. If I02R is used to indicate a certain amount of solid heat conduction and heat radiation, Equation 1 can be expressed as I2R = Ap + I02R (5) A = αΛπda(T-T0) (6) I0 is the current of the thin wire when the pressure is 0, which is to compensate for the heat loss caused by solid heat conduction and heat radiation. The formula A is a constant that does not depend on the pressure. If the resistance R of the thin wire, the current I0, and the constant A are known, the pressure P can be obtained by the equation (5). Calibration of resistance vacuum gauge Generally, the zero point is calibrated first, and then the full scale is calibrated. (1) Calibration zero point. To calibrate the zero point, vacuum the vacuum system to be tested. Once the ionization gauge measures a vacuum higher than 1.0^-1Pa (such as 9.9 X10^-2Pa), press the "zero calibration" button, the corresponding indicator light is flashing or flashing quickly, and the vacuum gauge is automatically Correct the zero point. When 1.0^-1Pa is displayed, it indicates that the regulatory zero point has been calibrated. For resistance vacuum gauges without automatic zero calibration, they can be manually adjusted via the potentiometer knob on the operator panel. (2) Fullness correction. After the zero point has been calibrated, its full scale correction is required. According to the requirements of the full-scale calibration process, the atmosphere of the furnace to be tested is placed in the atmosphere to ensure that the position measured by the resistance gauge is atmospheric, and it is operated at atmospheric pressure for about 10 minutes. Press the "Fullness" button, the corresponding indicator lights up or flashes quickly, the vacuum gauge automatically corrects the fullness. When 1.0^5 Pa is displayed, it indicates that the regulation fullness has been calibrated. For resistance vacuum gauges without automatic full-scale calibration, they can be manually adjusted via the potentiometer knob on the operator panel. 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