Abstract: A method and an apparatus for workpiece installation capable of carrying out workpiece installation operation without a stopping of a rotational motion of a rotatable table member. In the apparatus, rotatable drum is continuously rotated while workpiece carrier member, provided along a circumference of the rotatable drum, for carrying a workpiece from a workpiece supply station to a workpiece installation station, which is capable of spinning on the circumference while carrying the workpiece, is controlled such that the workpiece carrier member spins while the rotatable drum rotates so as to move along a prescribed trajectory which is preferably a cycloidal or quasi-cycloidal trajectory, and that the workpiece is picked up by the workpiece carrier member at a prescribed pick-up position on the workpiece supply station and released at a prescribed installation position on the workpiece installation station.

Abstract: A density meter which is immersed in a liquid to be measured to optically measure the degree of opacity thereof is disclosed. The meter comprises a density measurement system in which the liquid is sucked into a transparent inner cylinder by moving a piston upwardly and the transmittance of the liquid is measured by an optical system provided outside the transparent inner cylinder, and a calibration system in which a calibration liquid flow path is formed. The outlet of the calibration liquid flow path is communicated with the transparent inner cylinder, and the outlet is above a position at which the end of the piston is set during density measurement. In calibration, the piston is raised to a position higher than the position of the outlet to introduce a calibration liquid into the inner cylinder to calibrate the density meter by the optical system.