<p>"Determination of Biomass" Apparatus for the determination of biomass in a suspension and its use in a fermentation apparatus. The apparatus comprises electrodes to be placed in the suspension through which an alternating voltage is applied. A capacitance dependent signal indicative of biomass concentration is generated by determining the ratio of the value of a voltage electrodes to the value of a quadrature component of a current signal. Improved in-situ measurement of biomass is obtained.</p>
