A system comprising: a flow meter comprising (i) a housing defining a chamber having a fluid inlet and a fluid outlet wherein at least a portion of the housing is substantially transparent to a first wavelength of light; and (ii) a first rotating element within the chamber configured to rotate as fluid travels through the housing , wherein the first rotating element comprises a detectable area which reflects light of the first wavelength differently than portions of the first rotating element that are not the detectable areas; an optical assembly comprising an optical emitter configured to emit light of at least the first wavelength into the chamber via the substantially transparent portion of the housing and an optical detector configured to detect light of at least the first wavelength reflected from inside the chamber ; characterized in that a capacitive sensor is positioned proximate the housing , the capacitive sensor comprising a first electrode , a second electrode , and a first insulator separating the first and second electrodes ; wherein the capacitive sensor is positioned on a first side of a capacitive sensor board , the first side of the capacitive sensor board facing the first sidewall of the housing ; and wherein the capacitive sensor board comprises a second side, opposite the first, and a ground layer and a powered layer each positioned between the first and second sides of the capacitive sensor board . a flow meter comprising (i) a housing defining a chamber having a fluid inlet and a fluid outlet wherein at least a portion of the housing is substantially transparent to a first wavelength of light; and (ii) a first rotating element within the chamber configured to rotate as fluid travels through the housing , wherein the first rotating element comprises a detectable area which reflects light of the first wavelength differently than portions of the first rotating element that are not the detectable areas; (i) a housing defining a chamber having a fluid inlet and a fluid outlet wherein at least a portion of the housing is substantially transparent to a first wavelength of light; and (ii) a first rotating element within the chamber configured to rotate as fluid travels through the housing , wherein the first rotating element comprises a detectable area which reflects light of the first wavelength differently than portions of the first rotating element that are not the detectable areas; an optical assembly comprising an optical emitter configured to emit light of at least the first wavelength into the chamber via the substantially transparent portion of the housing and an optical detector configured to detect light of at least the first wavelength reflected from inside the chamber ; characterized in that a capacitive sensor is positioned proximate the housing , the capacitive sensor comprising a first electrode , a second electrode , and a first insulator separating the first and second electrodes ; wherein the capacitive sensor is positioned on a first side of a capacitive sensor board , the first side of the capacitive sensor board facing the first sidewall of the housing ; and wherein the capacitive sensor board comprises a second side, opposite the first, and a ground layer and a powered layer each positioned between the first and second sides of the capacitive sensor board . <EOS>