AM-FLS Fork Level Switch

A fork level switch answers one question and only one: is the medium at this height, or is it not. Two piezo crystals drive the fork at roughly 200 Hz; when the medium covers it, the vibration stops and the contact changes. There is no reading to calibrate and no zero to drift, which is why this is still the instrument on the tank that has to work after ten years of being ignored.

It earns its place on the awkward media — cement, sugar, plastic pellets, dye powder, milk, pulp, sludge with sediment — and it loses it on anything that coats the fork, anything that attacks the copper alloy or stainless tines, and particles larger than 10 mm. Above 60 °C in the vessel the remote version keeps the electronics out of the heat; the rest is placement, and the datasheet’s four wrong ways to mount it are worth reading before the nozzle is welded.