Stilling well is a cylinder shaped cage installed within a tank to protect level instrumentation such as displacer from fluid agitation that would result measurement error.
The stilling well should be perforated (provided with holes) to allow the level of fluid inside and outside stilling well within a tank be always equal.
Stilling well shall have diameter with size providing adequate gap between stilling well and displacer. This is to avoid liquid or particle being clogged in between.