A capacitance-type transducer used for the measurement of bending strains test elements which are not sufficiently strong to support a strain element or for test elements in which a strain element would strengthen the test element and not give an accurate test. The transducer is formed by a spring wire which has a portion perpendicular to the test specimen with a U-shaped end extending from the perpendicular portion. One portion of the U-bend has an insulator about the wire where the insulator parallels the test specimen surface and is in contact therewith. The end of the wire has a flat conductive plate secured thereto with the flat plate parallel with the specimen. The spacing between the flat plate and the specimen forms the capacitance spacing which changes as the specimen is strained in a direction perpendicular to the flat plate. The distance between the flat plate and specimen is represented by a change in capacitance which is measured by an oscilloscope. The change in capacitance is used to calibrate the strain on the specimen.

Apparatus for measuring at least one component of the forces applied to a beam comprises supports at a pair of spaced locations along the beam, each support having an arm, the arms extending axially toward each other. One arm carries a displacement sensor and the other arm carries a transmission element coupled to the moveable part of the displacement sensor. Each support represents arbitrary points d and e, and measurement of the component parallel to a straight line through the displacements of the point d with respect to the point e makes it possible to obtain the above-mentioned component. This result is independent of the position of the resultant of the forces applied to the beam with respect to the point of measurement.

Above the base are a pair of arms pivotally mounted about a common axis and extending in opposite directions from the axis. At the distal ends of the arms are a pair of downwardly extending pins which form sensors and position the arms at various angular positions depending upon the tension of the tensioned sheet upon which the base rests. A pair of plates extend upwardly from the arms, intercepting a light beam. The amount of the beam intercepted will vary depending upon the angular position of the arms. A photo detector is positioned to receive the unintercepted part of the beam and to produce an electrical signal varying with the amount of light received. A digital voltmeter provides a visual indication of the magnitude of the electrical signal.

Apparatus for removably connecting a strain cell to a polished rod of a well pumping unit and for preventing the development of strain cell output signals due to bending of the polished rod. The strain cell is connected to a frame member which can be clamped to the polished rod where strain cell output signals are obtained due to a change in tensile load on the rod. A pair of hinges, between the frame member and the polished rod, minimizes the development of strain cell output signals due to bending of the polished rod. The frame member can be adapted to mount on a variety of sizes of polished rods. The apparatus can be removed or replaced without the use of special skills or special equipment.

A devised strain meter detects displacement on the lateral side of the receptacle after magnification of the displacement by a lever in the receptacle. A cavity exists near the middle of the receptacle with a lever and a detector along the lateral side of the receptacle of the strain meter. Wires for signal and power lines of other strain meters are easily passed through this cavity. This mechanism with a cavity near the middle of the receptacle is very useful for an array observation of strain in the ground and/or in a solid construction.