In challenging environments, ultrasonic sensors have the advantages of longer and wider sensing ranges and ability to ignore color, ambient noise, and dust. Topics covered include a short course on ultrasonic sensors and the advantages of the newest ultrasonic sensors, which include features that facilitate monitoring and make monitoring more precise and efficient. Multiplexing also allows sensors to be mounted in close proximity to stagger ultrasonic bursts to prevent two or more units from concurrently sending or receiving signals (crosstalk). Multiplexing is very useful, particularly for assembly lines where multiple sensors have to monitor products that are close to each other on the line. Addition of serial communications abilities is another improvement. For instance, Pepperl+Fuchs provides a series of RS-232 programmable ultrasonic sensors that provide high-resolution control of switch point/span settings, compensation for turbulent or unstable target surfaces, and access to extended sensing ranges and other parameters. Therefore a sensor can be adjusted to provide optimal performance under current applications conditions and to show those parameters or measurements to a PC. A software program provides a communications link between an RS-232 programmable ultrasonic sensor and a Microsoft Windows-based computer. Programmable sensors can be beneficial for such applications as distance measuring in tight spaces and liquid level control for agitated liquids.