KOBOLD KSK plastic low volume flow meters, or rotameters, and flow switches operate on the basis of the well-known variable area principle. The media flows upward through a conical measuring tube. The float is lifted by the flowing media and indicates the instantaneous flow rate on the scale attached to the flow meter. These are constructed of all-plastic materials with bodies made of polyamide or polysulfone to handle aggressive media. For the control of flow setpoints, a bistable switch can be provided for the instrument. Available reed contacts or transistor switches can be used to monitor and alarm on an upset flow condition. The transistor switch has an LED on the contact housing to indicate switching status.