Selectable servo ratio and dual speed control system for large centrifuge units

In a large centrifuge unit having a variable RPM arm and a main arm frequency signal fm the improvement comprising,

• a frequency synthesizer generating a precision frequency signal fp adapted to effect a selected centrifuge main arm RPM,
• digital means for digitizing the precision frequency signal fp and the centrifuge main arm frequency signal fm and for generating an acceleration signal and a deceleration signal in response to relative values thereof, said acceleration and deceleration signals effecting control of the centrifuge main arm RPM,
• summing means receiving the precision frequency signal fp from said frequency synthesizer and outputting a current control signal,
• a servo ratio selector circuit connected between said frequency synthesizer and said summing means and generating servo control signals, said servo control signals effecting selected operating mode ratios,
• a power supply means to drive the centrifuge main arm, said power supply means being current controlled, said power supply means receiving said current control signal from said summing means and providing an output current signal in response thereto, said output current signal driving said centrifuge main arm at a corresponding RPM,
• a track and hold circuit connected between said summing means and said power supply means,
• a digital tachometer receiving said precision frequency signal fp, said digital tachometer converting said precision frequency signal fp to a velocity signal, and
• an analog function module connected to said digital tachometer to receive said velocity signal, said analog function module providing an analog voltage proportioned to said velocity signal, said analog function module being connected to said summing means.