Load cells, the heart of weighing systems, are mechanical devices that use strain gages to provide a measurable electrical output which is proportional to the force applied. The electrical output can be either an analog voltage or current output, or a digital on/off output.
Used for tension, compression, and or shear measurement, load cells are packaged and oriented to perform in testing equipment, electronic scales, and monitoring systems. Tension load cells are used for measuring forces that are in-line and "pull apart". Compression load cells are used to measure forces that are in-line and "push together". Shear load cells are used to measure tension or compression forces that are offset (not in-line). When selecting load cells, there are many form factors or packages to choose from to insure their physical size is compatible with space available for the application, such as inside an electronic weighing scale.
The strain gage is a resistive sensor whose resistance changes based upon the applied strain. A strain gage is attached to some structure, and when that structure is deformed (tension, compression, shear), the resistive strands in the strain gage follow the structure deformation, causing an electrical resistance change. This change in resistance is converted to units of strain or stress.
Strain gages are used in transducers that measure force, pressure, and tension, and are often used providing stress analysis in structures such as airplanes, cars, machines, and bridges.
When specifying strain gages one must consider the application variables, such as operating temperature, the state of the strain (including gradient, direction, magnitude, and time dependence), and the stability required by the application.
For more information about strain gages and load cells, contact AP Corp. Call them at 508-351-6200 or visit their web site at https://a-pcorp.com.