Microwave Barrier Switch detects the upper and lower limits of silo, hopper, etc.The microwave system enables non-contact detection and easy maintenance. Further the mounting positions can be easily decided because detection works when the accumulation of material blocks the straight line between transmitter and receiver. Max.detection distance 100m realized. Small detection area dia.25mm of transmitter/receiver enables easy installation. Free voltage model from AC80 to AC240V reliable against unexpected voltage variation and disturbance noise. Exact and stable sensitivity setting can be made easily. Self-diagnosis function automatically detects decrease of sensitivity due to adhesion etc.