How Do Load Cells Work?
Interface, Inc.
The World Leader in Force Measurement Solutions since 1968. The most accurate load cells, torque sensors + strain gages.
A load cell?converts an applied mechanical force, whether that is tension, compression, or torsion, into a measurable electrical signal. Any change in force, increases or decreases the signal output change in proportion.
A load cell has two basic components. It has a spring element that is often known as a flexure that mechanically supports the load to be measured and a deflection measurement element that responds to flexure movement resulting from the application of force.
In simpler terms, there is a bending beam under the load and when weight or force is applied, the change in bend (deflection) results in change in output.
A load cell’s basic function is to take applied force and convert it into an output signal that provides the user with a measurement. This process of converting a force into data is typically completed through a Wheatstone bridge that is comprised of strain gages.
Strain Gage Load Cells
A?strain gage?is typically constructed of an exceptionally fine wire or metal foil that is arranged in a grid-like pattern. Strain gages are strategically placed on the load cell flexure and bonded securely, such that the force induced deflection of the flexure causes the gages to stretch or compress. Thus, when tension or compression is applied, the electrical resistance of the strain gages changes and the balance of the Wheatstone bridge then shifts positive or negative. Fundamentally, the strain gages convert force, pressure, or weight into a change that can then be measured as an electrical signal.
Why use strain gages in load cells? Strain gage characteristics include thermal tracking, temperature compensation, creep compensation, frequency response, and non-repeatability. The major advantage of the strain gage as the deflection measuring element is the fact that it has infinite resolution. That means that no matter how small the deflection, it can be measured as a change in the resistance of the strain gage.
The strain gage is the critical foundation of a load cell and the most vital component for accurate and reliable measurements. One thing to understand about Interface load cells is that we develop our own strain gages in-house using a proprietary manufacturing process to ensure premium performance.
In addition to strain gage load cells, there are also two different less common load cells that use a diverse types of data collection method. This is defined as pneumatic and hydraulic methods.
Pneumatic Load Cells?
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These load cells are typically used for measuring lower weights with high degrees of accuracy. They measure weight in terms of force-balance, meaning that weight is reported as a change in pressure. Key advantages of pneumatic load cells are their resistance to electrical noise and inability to spark, in addition to their low reactivity to temperature changes.
Hydraulic Load Cells
As the name suggests, these load cells utilize fluid pressure for measurement. Like pneumatic load cells, hydraulic load cells balance force by measuring weight as a change in pressure, and the pressure of the fluid rises because of an increase in force. These load cells have no electric components, allowing them to perform well in hazardous conditions.
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