The ultrasonic web edge sensors bks+ sense the edge of web-form materials which are decoiled from a spool and guided through a processing machine. The position of the edge is required in order to readjust the web run in such a fashion that the material run always remains “on track”.
The ultrasonic web edge sensors are structured as a fork sensor and work as a through-beam barrier. A transmitter is located in the lower prong of the fork, which emits continuous ultrasound. A receiver transducer in the upper prong receives the emitted ultrasonic signal and evaluates its intensity. A web material inserted in the fork of the web edge sensor more or less covers the sound path between the transmitter and the receiver. The intensity of the receiver signal varies depending on the degree of coverage. This change is issued as an analogue signal 4-20 mA or 4–20 mA for the purpose of controlling the web run.
