Mixing and blending controllers govern the ratio, mixing or blending parameters of two or more ingredients in a process automation system (PAS). They are used to control the addition of gas or air, liquids, and/or solids. Mixing controllers and blending controllers receive inputs from sensors and systems such as weigh feeders, belt conveyors that control the flow of bulk solids by continuously weighing material and adjusting the belt speed accordingly. Choices for mixing and blending controllers with regard to functionality include: rate indication, data logging, and totalizing. The user interface for a mix controller or blend controller may consist of a digital front panel or analog components such as knobs and switches. Computer-programmable, web-enabled, and network-ready mixing controllers and blending controllers are also available. A mix controller or blend controller with digital controls may include human machine interface (HMI) software or provide supervisory data acquisition and control (SCADA) functionality. Mixing and blending controllers that incorporate a programmable logic controller (PLC) or interface with a personal computer (PC) are also available.