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The rocker pin load cell is a transducer that converts a load into an electrical signal, usually by the use of four or more strain gauges in a Wheatsone bridge configuration.

The rocker pin load cell is basically a compression strut that that has each end formed into a spherical surface. By loading the rocker pin through load cups of a different spherical radius, the assembly can be made to be self-uprighting and self-centering.

The rocker pin load cell provides a convenient means of providing a self-centering capability to the load cell installation, thereby eliminating the effects of parasitic stresses that are often introduced by shock loads and by temperature changes (expansion/contraction). The typical area of application is in truck scales (weighbridges) and other large industrial platforms such as those found in railway scales and in bulk materials handling installations.

The rocker pin load cell is usually provided with a kit of parts that include upper and lower hardened steel (or hardened stainless steel) load cups that have internal spherical surfaces that are of a different radius to that of the rocker pin ends. The combination of this detail and the height of the rocker pin provides the self-uprighting properties that are essential for the stability of the installation.

In the event that the limit of the self-uprighting capability is exceeded, the installation will be liable to collapse unless proper restraining rods and bump stops are provided. Such restraints are usually provided anyway as safety measures in most heavy industrial installations, to protect against the accidental impact of transportation vehicles such as fork lift trucks or dump trucks. Therefore the overall cost effectiveness of the rocker pin installation is not adversely affected.

Multiple load cell outputs are wired in parallel and their outputs are then summed to give the total load result. In the case of floor scales and other applications where the load can be positioned off-center, then it may be necessary to trim the outputs of the individual load cells so that the load result is the same, regardless of load position on the scale. Such devices are known as summing junction boxes or trimming boxes, and can be found in the OTHER PRODUCTS selection on the Mantracourt website.

The output of such load cells is usually in the region of 2 to 3 mV/V at full load, which makes them suitable for use with any of Mantracourt's strain gauge amplifiers, digitisers and controllers.