Abstract: An improved photoelectric displacement detector is disclosed which includes (a) a light receiving part (1) having a pair of solar battery panels (1b, 1c) vertically arranged adjacent to each other, (b) a vertical motion mechanism (2) which is driven by a motor (3) to vertically linear-shift the light receiving part (1), (c) a vertical light quantity difference detection part (4) for detecting, based on signals from the solar battery panels (1b, 1c), a difference between the quantity of light received in the solar battery panel (1b) and the quantity of light received in the solar battery panel (1c) and (d) a CPU (5) for controlling the operation of the motor (3) according to the received light quantity difference detected by the vertical light quantity difference detection part (4). Reference laser light is sent onto the light receiving part (1) and the light receiving part (1) is vertically shifted in order that the aforesaid received light quantity difference is cancelled to zero.

Abstract: A reflector provided on a land is automatically collimated in such a way that it always comes to the center of the field of view of an automatic tracking type measuring apparatus provided on a platform. When the platform moves vertically or horizontally in this state, the reflector moves within the field of view. Then, a drive signal is supplied to a servo system to cause the reflector to come to the center of the field of view. Based on data measured by the apparatus, the platform is positioned.

Abstract: An improved desilter for drilling muds consists of one or more hydrocyclones with certain features providing for better separation of large particles from the mud. Drilling muds used in drilling oil wells and the like give substantially improved performance when the larger particles are removed therefrom and the mud consists of fine particles having a narrow range of particle size.An improved hydrocyclone for removing coarser particles from the drilling mud has overflow and underflow outlets which discharge openly rather than into a collection manifold. The overflow outlet is in the form of a controllable syphon which may be adjusted in syphon length or which may include means to adjust the effective length of the syphon leg. The adjustment of the syphon leg controls the overflow of the thin, more uniform mud and effects a superior separation of the larger particles from the mud.