I'm using General-purpose 61F Floatless Level Controllers with cable conductor of 2 mm2 and a length that is less than 1 km, but it malfunctions. Is there a solution for this?
It's possible that the cable conductor diameter is too large. Try changing to 0.75-mm2 conductor, or replace 61F with a long-distance model.
*Stray capacitance increases with thick cable diameters, which shortens the applicable cable length.