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A radar sensor detects unwanted reflections when something other than the intended target enters its beam: tank walls, nozzles, agitator blades, internal fittings, weld seams or nearby metal structures all return echoes, and mounting angle or position decides whether those echoes compete with the real one. The first safe check is a geometry review on drawings: map what physically sits inside the beam at every target position, then compare with the sensor's mounting location and beam direction. Configuration changes (blanking, thresholds) belong to the exact model manual; never open or climb into a vessel for inspection without the site's confined-space and process-safety procedures.
Radar sees everything in the beam, not just the target. Microwaves reflect from any surface with suitable dielectric contrast — metal strongly, but also walls, fittings and buildup. "Unwanted reflection" means the echo list contains more than the target.
False echoes are usually fixed, the real echo moves. A wall or nozzle echo sits at one distance regardless of level; that property is the basis of both diagnosis and the blanking techniques below.
Mounting position and angle decide the problem before configuration does. A sensor aimed across an agitator or too close to a wall will fight geometry forever; relocation beats parameter tuning.
Blanking (false-echo suppression) is powerful but must be learned with the real installation. Suppression configured without verifying the real target can hide the true echo instead — configuration is manual-plus-verification work.
Some vessels need a site review, not a sensor swap. Complex internal geometry, foam, or multiple measurement points justify a structured review with the sensor manufacturer before hardware changes.
This article covers three unwanted-reflection patterns:
Static false target — the reading locks onto a fixed distance that is not the target (classic wall/nozzle echo);
Intermittent false target — the reading jumps to a false echo only at certain levels, agitator positions or process states;
Echo confusion after a change — correct before, wrong after a nozzle extension, fitting addition or sensor relocation.
For level applications specifically, media-related difficulties (dust, foam, condensation on the antenna) are a selection topic owned by the level-sensor selection guide ({{URL_E07}}); this article covers the reflection/geometry side.
