A leveling pole comprising telescopically slidable inner liners, wherein an outermost liner is provided detachably with a case for receiving a tape-line connected to an innermost liner through the outermost liner and each inner liner except for the innermost liner, the tape-line being bilaterally graduated in selected two kinds of linear measure systems to alternatively indicate one of the graduations corresponding to the movement of each inner liner to and from the outermost liner through an aperture which is formed on the case and covered with a shutter slidable across the aperture. The invention further involves the art wherein a hook is detachably mounted onto the foremost end of the innermost liner thereby making it possible to measure the height of an object exceeding the total length of the pole.

The measuring probe at the top end of a telescopic tube of a radiation counter for measuring an ionizing radiation is connected to the measuring circuit via a thin ribbon cable capable of being wound onto a take-up drum of a metering instrument. A thin steel tape is attached to the ribbon cable and extends in parallel therewith. When a mutual twisting of the individual sections of the telescopic tube occurs while the same is being extracted, the ribbon cable is prevented from being twisted as well, because the measuring probe is axially rotatable and runs in ball bearings, and because the thin attached steel tape has the necessary torsional rigidity. Together with the steel tape, the ribbon cable can be wound onto the take-up drum even at very low temperatures (such as -30.degree. C.) without any noteworthy additional winding force being required to this end.

An extensometer for measuring changes in the vertical distance between the roof and floor of a mine opening which comprises; a pair of rigid telescoping members, a tension spring securing said members to each other in a telescoping relationship, a hook for attaching a non-extensible cable to each of said members, and an indicator for determining telescopic movement of said members. The extensometer of this invention is utilized by securing one of said telescoping members to the roof of the mine and the other telescoping member to the floor of the mine with the axis of said members being disposed along the vertical. The telescoping members are secured, under tension, to the mine roof and floor by means of a non-extendible cable such as a steel cable. The indicator for determining the telescopic movement of the members may be a pair of lugs or flanges or other indicating marks, each member of which pair is affixed to a separate telescoping member.

A measuring system is disclosed for surveying and very accurately positioning objects with respect to a reference line. A principal use of this surveying system is for accurately aligning the electromagnets which direct a particle beam emitted from a particle accelerator. Prior art surveying systems require highly skilled surveyors. Prior art systems include, for example, optical surveying systems which are susceptible to operator reading errors, and celestial navigation-type surveying systems, with their inherent complexities. The present invention provides an automatic readout micrometer which can very accurately measure distances. The invention has a simplicity of operation which practically eliminates the possibilities of operator optical reading error, owning to the elimination of traditional optical alignments for making measurements. The invention has an extendable arm which carries a laser surveying target. The extendable arm can be continuously positioned over its entire length of travel by either a coarse or fine adjustment without having the fine adjustment outrun the coarse adjustment until a reference laser beam is centered on the target as indicated by a digital readout. The length of the micrometer can then be accurately and automatically read by a computer and compared with a standardized set of alignment measurements. Due to its construction, the micrometer eliminates any errors due to temperature changes when the system is operated within a standard operating temperature range.

The retractable tape of the present invention includes a housing from which a flexible, metallic retractable tape can be withdrawn. The tape has, at its outer end, a telescoping arm which extends at right angles to the zero-mark on the tape. A second telescoping arm is fastened to the housing from which the tape is withdrawn and is positioned at right angles to the tape and housing at a point where the tip of the telescoping arm is in alignment with the index marker on the housing. The telescoping arms can extend twelve inches from the tape and housing. The tape can be retracted into the housing, and the arms can be telescopically contracted so that when the tape is retracted into the case and the arms are contracted, the device occupies a minimal space in a mechanic's toolbox.