Low Profile Load Cells versus Simple Single Column Load Cells

Interface standard load cells are designed around either the bending beam, the shear beam, or the pipe column. To understand the reasons behind this metrology and engineering decision, we must understand the simple column cell versus the low profile design.

Based on quality, performance, and durability, Interface trademarked our LowProfile® design more than five decades ago. This post contains information from Interface’s Load Cell Field Guide. You can download a free copy of this essential test and measurement tool here.

While a simple single-column load cell may appear straightforward compared to a LowProfile Load Cell, its design is far from simple. The physical components are relatively easy to manufacture, but several intricate characteristics severely limit its practicality for use in high-accuracy test and measurement applications. Interface’s precision pipe column designs are not simple column load cell designs. The following details the drastic differences.

The Interface LowProfile Load Cell, a pancake design, is dramatically better than the simple single column cell in every respect. Here is an inside look at the LowProfile design.

LowProfile Load Cell Considerations

• The thermal path is massive and surrounds the whole cell. The thermal path between the outside surface and all the gages is very short. Temperature gradients are almost non-existent, and they settle out very quickly.
• Compensating resistors are mounted on the flexure near the gages.
• The diaphragms are used only as a sealing mechanism, not as a support, so they do not introduce appreciable errors into the cell.
• There are two opposing diaphragms, one on the top and one on the bottom of the cell. Their opposing forces due to pressure are equal and opposite, thus canceling out pressure effects.
• The cell is short and squat, thus making it much easier to integrate into system designs. Column cells range in height from 6″ to 24″, compared to a LowProfile cell’s height with a base of 2.5″ to 6.5″.
• The design is intrinsically moment-canceling and rotationally symmetrical. In addition, special testing and adjustment in the factory enhance moment cancellation. Learn more by reading: What is Moment Compensation?
• Since the flexure’s cross-sectional area does not change appreciably with loading, the output is intrinsically more linear and symmetrical between tension and compression modes.
• At the same stress level in the flexure, the output of the shear beam cell is up to 2.5 times that of a column cell.

The overall proprietary Interface LowProfile design is more compact, with all the components bonded to the flexure structure, making it better able to withstand the 100 million-cycle fatigue life. Our standard 1200 “Blue” LowProfile Load Cell is the most popular load cell in the market and is used in testing labs and industry applications worldwide.

Simple Single Column Load Cell Considerations

• One of the most significant drawbacks of a simple single column load cell is its thermal path. This path, which is long and has a thin cross-section, can lead to prolonged temperature stabilization. For instance, if heat is applied to one side of the case, the case will expand on the hot side, causing a zero shift in the column. This thermal issue is a critical limitation that needs to be addressed.
• If heat is applied to the doghouse side of the cell, the compensating resistors will change resistance before the column sees the temperature change. Thus, the resistors will attempt to compensate for a change that has not yet occurred, causing a zero shift and an output shift.
• The diaphragms are an important support, keeping moment loads away from the column. However, since they are outside of the gaged areas of the column, they are a non-gaged parallel path, which introduces their errors (nonlinearity, hysteresis, and thermal response) directly into the measurement path. The diaphragms cannot be enough to protect the column from pure moment loads without introducing significant errors.
• Changes in pressure due to barometric change or altitude testing act on the diaphragm, causing a zero shift. For example, a six-inch diameter diaphragm would induce a force change of 375 pounds into a column cell from sea level to space orbit altitude in a test.
• Since the column’s cross-sectional area changes with loading and is different between tension and compression modes, the output is non-linear and unsymmetrical. Non-linear semiconductor gages can compensate for the non-linearity, but only in one mode.

On the other hand, low profile load cells offer a more compact solution, making integration into testing equipment much easier. This advantage not only enhances the efficiency of the equipment but also opens new possibilities for testing in confined spaces.

If you have questions about which type of load cell is best for your testing application, please get in touch with our application engineers or use our Load Cell Selection Guide.