A solids level indicator assembly comprising: a shaft housing (526; 626) having a housing interior end and a housing exterior end, wherein the shaft housing exterior end is disposed outside a vessel, and wherein the shaft housing (526; 626) fixedly engages the vessel so as to resist torsional movement; a torsion shaft having a shaft interior end and a shaft exterior end, wherein the torsion shaft is disposed within the shaft housing (526; 626) such that the shaft interior end extends past the housing interior end to engage a paddle cap (508; 608) disposed within the vessel; a paddle (517; 617) engaging the paddle cap (508; 608) perpendicularly to a length of the torsion shaft so as to cross a path of solids in the vessel, wherein the paddle (517; 617) torsionally communicates with the shaft interior end; and a support structure engaged to the solids level indicator assembly; characterized in that the assembly further comprises: a modular external sensor having a rotary end adjacently disposed to a stationary end, wherein the rotary end is adjacently disposed to the shaft exterior end and the shaft exterior end torsionally communicates with the adjacently disposed rotary end, and wherein the modular external sensor is configured to be slidably disengaged from the shaft exterior end; and a torsion spring (528; 628) disposed around the support structure, wherein the torsion spring has a first spring end (564; 664) distally disposed from a second spring end (566; 666), wherein the first spring end (564; 664) is in torsional communication with the modular external sensor, and wherein the second spring end (566; 666) fixedly engages the support structure such that the torsion spring (528; 628) bends to store torsional energy when solids exert a downward force on the paddle (617; 617) and wherein the torsion spring (528; 628) releases the stored energy into the torsion shaft in a direction opposite the direction of the torsional force exerted on the paddle (517; 617) by the mass of solids when the force exerted by the solids subsides. a shaft housing (526; 626) having a housing interior end and a housing exterior end, wherein the shaft housing exterior end is disposed outside a vessel, and wherein the shaft housing (526; 626) fixedly engages the vessel so as to resist torsional movement; a torsion shaft having a shaft interior end and a shaft exterior end, wherein the torsion shaft is disposed within the shaft housing (526; 626) such that the shaft interior end extends past the housing interior end to engage a paddle cap (508; 608) disposed within the vessel; a paddle (517; 617) engaging the paddle cap (508; 608) perpendicularly to a length of the torsion shaft so as to cross a path of solids in the vessel, wherein the paddle (517; 617) torsionally communicates with the shaft interior end; and a support structure engaged to the solids level indicator assembly; a modular external sensor having a rotary end adjacently disposed to a stationary end, wherein the rotary end is adjacently disposed to the shaft exterior end and the shaft exterior end torsionally communicates with the adjacently disposed rotary end, and wherein the modular external sensor is configured to be slidably disengaged from the shaft exterior end; and a torsion spring (528; 628) disposed around the support structure, wherein the torsion spring has a first spring end (564; 664) distally disposed from a second spring end (566; 666), wherein the first spring end (564; 664) is in torsional communication with the modular external sensor, and wherein the second spring end (566; 666) fixedly engages the support structure such that the torsion spring (528; 628) bends to store torsional energy when solids exert a downward force on the paddle (617; 617) and wherein the torsion spring (528; 628) releases the stored energy into the torsion shaft in a direction opposite the direction of the torsional force exerted on the paddle (517; 617) by the mass of solids when the force exerted by the solids subsides.