In some applications the process flow does not keep the prism clean because of sticky process medium or low flow velocity. In these applications the prism can be automatically cleaned by installing a wash system.
The prism wash settings for sensors A and B are independent of each other. The wash system is active if a relay has been configured to be a wash relay, see Configuring relays, and the wash time is not zero. An automatic wash function can be configured so that both sensors have different parameters.