Low cost micro variable area flow switch. The float is controlled by a spring in a cylindrical measuring tube. The passing medium pushes the float in the di-
rection of flow. The reed contacts on the outside of the measuring tube are
sealed. When the float reaches the reed contact, the switch closes. When the
flow increases, the float continues to move upward until the built-in float
baffle, while keeping the switch closed, thus ensuring that the function of
the bistable switch can be realized at any time. Reed contact can be adjusted
in all switching range of the instrument.