Dwyer Instruments Flow Switches Flow switch sensors with an electrical contact output at a specific flow rate have different types of switches, which are a paddle, thermal, piezo, and shuttle/piston SERIES FS-2 VANE FLOW SWITCH SERIES V4 FLOTECT® VANE-OPERATED FLOW SWITCH SERIES V8 FLOTECT® VANE OPERATED FLOW SWITCH SERIES V6 FLOTECT® MINI-SIZE FLOW SWITCHES