A low-cost integrator for preparative ultracentrifuges

An integrator is described for the measurement of the time integral ∫₀^t rpm²dt in preparative ultracentrifuge where linearity exists either (a) between tachometer generator ac voltage amplitude and rpm (e.g., Sorvall RC2-B) or dc voltage and rpm, or (b) between the square-wave frequency from the tachometer generator and rpm (e.g., Beckman L2-65B). The construction and the precision levels of an integrator for Sorvall RC2-B preparative ultracentrifuge in the range 0–10,000 rpm and for Beckman L2-65B preparative ultracentrifuge in the range 0–40,000 rpm are described.