Tags – How Do Load Cells Work?
Load cells are sensors that are used to measure weight or force.
They are commonly found in industrial and manufacturing settings, but they can also be used in a variety of other applications.
In this comprehensive guide, we will discuss the different types of load cells, how they work, and some of the common applications for them.
What Are Load Cells?
Most industrial weighing equipment contain load cells, which are essential components.
The most basic definition of a load cell is that it measures weight – or, more accurately, directional force – by means of a combination of springs and strain gauges converted into an electrical output.
Depending on the intended application and environment, load cells come in a variety of forms and standards.
Some types, however, require calibrated proving rings to determine load displacement – although this is less common. Strain gauge load cells are widely used in the weighing sector, with the exception of certain laboratories where precise mechanical balances are still utilised.
Among the many sorts of load cells available, distinct types and designs can be distinguished in two key ways:
- By the specific technique they use to detect weight (compression load cells, tension load cells, and other measurement types)
- By the type of output signal generated (hydraulic load cells, piezoelectric load cells and other various configurations)
It should be stated that, in a strict sense, any true load cell will always be designed to operate (and should therefore be aligned) in the direction of gravity.
However, the term “load cell” is frequently used to refer to a wide range of force-sensing device kinds, many of which are specifically designed to detect forces applied from all directions.
Many workplaces nowadays have a similar meaning for these phrases, so it’s good to be precise about the sort of device you’ll be using for your intended application when calculating load cell prices or planning to purchase load cell components.
How Do Load Cells Work?
Spring elements attached to strain gauge materials (usually foil meshes or semiconductors) are most often made of steel or aluminium, resulting in a strain gauge that is both extremely durable and somewhat elastic.
Deformation will occur to some extent under enough pressure, whether it is down force from above (compression) or a pulling force from below (tension), before returning to their original form and shape. The strain gauges can precisely measure the degree of this deformation in the spring components.
In a typical load cell, it’s this micro deformation analysis that is transformed into an extremely precise weight reading using electronic means. In this way, directional pressure affects a load cell transducer and generates an electrical signal that is proportional to the measured force.
Because they are sensitive to changes in temperature and humidity, load cells may be affected by a variety of external factors that must be adequately controlled, monitored, and adjusted.
Overall temperatures, for example, might influence the structure (and therefore electrical resistance) of any material, as well as a wide range of other environmental issues such as bad weather, dampness and dust ingress, and changes in ambient conditions between sites.
Types of Load Cells
In the UK and the rest of the world, there are several load cell types and configurations available for industrial, manufacturing, and household usage.
In this section, we will give a brief outline of each of these types and what sorts of applications they might be best suited to.
Compression Load Cells
A compression load cell measures downward or lateral “pushing” forces only, much like a traditional weighing machine. They are also known as “column load cells,” “pancake load cells,” or “donut load cells.”
They’re often equipped with an integrated button design, making them a lightweight and efficient type of load cell for use in tight spaces. They’re especially prevalent at silo and boat weighing stations in industrial settings.
Tension Load Cells
A tension load cell is a type of strain gauge that measures forces that “pull” on it – usually from below – in the same way as a hanging digital scale at a grocery store fresh produce aisle.
Tension load cell transducers (also known as tensile load cells, tension links, or load links) are frequently used on an industrial scale for weighing vessels and suspended hoppers, material research and testing, laboratory environment general force measurement applications, and in aerospace process monitoring.
Hydraulic Load Cells
Hydraulic load cells incorporate a diaphragm attached to the piston that measures displacement under force. The tube of filling fluid is compressed or expanded as pressure rises or falls, which is then detected and converted by the load cell into a readout.
Hydraulic pressure load cells are frequently used in riskier, more environmentally harsh, or difficult-to-reach places because of their greater robustness compared to the delicate electrical circuitry of many other load cell types.
That said, they are typically used in simple industrial and agricultural weighing applications, where common environmental challenges include moisture, dirt or chemical exposure.
Micro Load Cells
Due to its compact nature, micro load cells usually rely on semiconductors, rather than foil strain gauges to sense and measure deformation.
They’re available in a number of configurations and styles, including both compression and tension varieties, and they may be used in a wide range of settings as bigger versions (as long as they can tolerate enough pressure).
Miniature or micro load cells are frequently used in cases where space is limited. They generally provide extremely accurate and precise readings ranging from 10 g to 2000 pounds, depending on the brand and model.
When shopping for micro load cells, it’s important to note that the majority of micro versions are restricted to measuring force from a single direction, so it’s vital to understand any “parasitic forces” (i.e., forces being applied from another direction) that may jeopardise the measurement’s accuracy or usefulness.
Piezoelectric Load Cells
In the case of dynamic loading, less sturdy strain gauge-type load cells can fail as a result of repeated application of sufficiently high dynamic load cycles.
Essentially, piezoelectric load cells function on similar principles to conventional strain gauge load cells – that is, they use the basic principles of deformation.
However rather than strain gauge foils, piezo cells are constructed of a different sort of transducer material. This material is able to transform the readings of dynamic and frequent force applied on it into an electrical output based on changes in resistance across the material.
Compared to regular load cells, piezoelectric sensors can’t be used for taking static measurements of weight or strain, because these create a fixed amount of charge on the material.
As a result, the voltage output does not change under static load, but some piezoelectric applications can be adapted with accessories like charge amplifiers to provide quasi-static measurements in the right conditions.
The Takeaway
An often overlooked but crucially important component, load cells are used in almost every modern industrial, manufacturing, weight-based sales or quality assurance environment you could name.
Today’s markets offer a wide range of configurations, brands, and load cell transducer types, and some understanding of what they are and how they function is necessary when selecting the best product type for your intended application.
To find out more, please get in touch today.
In the meantime, take a look at our Vehicle Weighing Solutions here.
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