Drawing methods of angle scale line on a common psychrometric chart

Analyses the relationship between state parameters of wet air, gives the definitions of the length to unit humidity and unit specific enthalpy, and presents two angle scale line drawing methods of two points and using angle measurement. According to representing method of coordinates in oblique coordinate system and the law of sine and the definition of angle scale, demonstrates the relationship between an angle scale and the angle between the angle scale line and an isohume on a common psychrometric chart, and takes it as the theory basis of drawing an angle scale line with angle measurement method. Illustrates the application of the two drawing methods of two points and using angle measurement, and compares the advantages and disadvantages of the two methods. The result shows that with the two point method can conveniently and quickly draw an angle scale line on a psychrometric chart.