Abstract: A teeter bed density control device is disclosed in a hindered-settling fluid classifier of the type having a teeter fluid supply system in a chamber with a fluidized teeter bed zone, an overflow zone and an underflow discharge outlet with the control device comprising an upper sensor for measuring average particle density from the upper boundary of the teeter bed zone to the top of the overflow zone, a lower sensor for measuring average particle density from the lower boundary of the teeter bed zone to the top of the overflow zone, a controller connected to the sensors for generating a compensating control signal based upon a preselected density standard and the average density of the teeter bed zone as determinable from the upper and lower average particle density measurements, and an actuable valve for regulating the discharge of the underflow discharge outlet with the controller being connected to the valve for actuation thereof responsive to the compensating control signal.