What is a Load Cell?
Let's review the operating mechanism, types, and recommendations for selection.
A load cell is a sensor that detects a force or mass and converts it into an electrical signal. They are used in a variety of fields, from scales and weighing instruments in day-to-day life to performance testing of presses and engines in industrial applications, helping to improve product quality and productivity. Since load cells are rarely visible, few people know what they are and how they operate. The following is an explanation of the mechanism and use cases of load cells, as well as key points for selecting types and products.
A Load Cell is a Sensor That Detects Force or Mass
A load cell is a sensor that detects force or mass (tension, pressure, torsional force, etc.) and can also be called a load transducer. Force or mass is converted into an electrical signal and output as an electrical signal. This signal is amplified and given a numerical value using a dedicated device connected to the load cell.
As force and mass values digitized by load cells can be stored as data, they are used for product inspection, data aggregation and other purposes throughout the industry.
For example, by measuring the mass of a product, it can be used to detect defective units that do not meet the specified weight. Measuring force and mass and recording them as data helps to improve product quality and productivity, and reduce costs.
Load cells are used in a variety of fields because they are relatively inexpensive and have a longer service life than other sensors.
Load Cell Mechanism
A load cell has components, where strain gauges attach, that deform in proportion to the applied force or mass. A strain gauge measures the ratio of the amount of change (strain) before and after deformation, When a load cell is deformed by a force or mass, the attached strain gauge is also deformed at the same time. The change in electrical resistance of the strain gauge due to deformation is converted into an electrical signal by the load cell, thereby giving the force and mass a numerical value.
The deformation of the load cell when a force or mass is actually applied is such a small change that it is not visible with the naked eye.
Load Cell Application Examples
Load cells are used in a variety of situations where force and mass are measured, from familiar products such as digital scales and weighing instruments to performance testing in engine development. Let’s take a closer look at an example of a load cell in use.
Medical Monitoring Equipment
Load cells can be used to monitor the weight of liquid in an intravenous drip bag and inform the user when it is time to refill the bag. By attaching it to the bed, it can also monitor changes in the patient’s weight and sleep patterns based on how the patient tosses and turns.
Home Appliances
Load cells are also used in systems that determine the cooking time for automatic heating and defrosting in microwave ovens based on the weight of the food. It is also used for controls such as with bidet toilet seats that require the user to be seated to use the bidet function.
Vehicle Crash Testing
Load cells are often used for testing the strength of products. Examples include measuring the impact of automobile collisions or the load of seatbelts when under tension. Other tests, such as material tensile and bending tests, are conducted to study strength and performance by measuring changes in the material.
Types of Load Cells
There are four main types of load cells, that relate to the shape of the components that deform when a force is applied. Let’s take a closer look at the characteristics of each type.
Diaphragm Load Cell
Diaphragm load cells are those with a circular-shaped body. A strain gauge is attached to the underside of the circle and a load is applied to the center to measure the amount of deformation. Compared to S-type and canister type load cells, this type is beneficial because the height of the body can be minimized.
S-type Load Cell
S-type load cells have a body in the shape of the letter S. A strain gauge is attached to the middle part of the S shape, and deformation can be measured by applying load to both ends. This type is suitable for measuring compressive and tensile loads, and is often used for fatigue and tensile testing of materials.
Canister Type Load Cell
Canister type load cells are those with a body in the shape of a cylinder. A strain gauge is attached to the center of the cylinder to measure the amount of deformation in the compressive direction of the cylinder surface when a load is applied from the top of the cylinder. They are suitable for measuring large loads.
Beam Type Load Cell
Beam type load cells are those with a main body shaped like a diving board. Strain gauges are attached to the top and bottom of the board to measure the amount of deformation caused when applying a load to one of the edges. Load cells are suitable for measuring bending and shear loads, and are also used for platform scales.
Load Cell Peripherals
Given the very small electrical signal detected by the load cell, instruments must be integrate to amplify the signal and convert it to a numerical value. Digital display indicators are commonly used, and selection involves considering the number visibility, required accuracy, and response time.
Graphic Digital Indicator “CSD-912B”
A graphic digital indicator that displays signals from load cells as weighing values. It provides various functions such as notifying weighing status via status indicator lamps, controlling weighing operations, and expanding weighing systems for measurements and instruments by connecting external devices. Up to 100 weighing objects can be registered.
“PR1626” Explosion-proof Interface
An interface between the load cell and instrumentation equipment is also available to minimize changes in load cell output due to temperature effects and to enable highly accurate measurements in harsh environments. Developed especially for load cells installed in hazardous locations, up to 4 load cells can be connected to the PR1626/60 and up to 8 load cells to the PR1626/61.
Load Cell Selection
Load cells come in a variety of shapes, including diaphragm and S-types. The appropriate load cell depends on the type of force or mass to be measured, such as measuring compressive or tensile forces or mass, so the load cell that best suits the purpose of the required measurements should be selected. When loads are being measured, attention should also be paid to the corresponding load capacity of the load cell. Select a unit with a margin greater than the rated capacity. The environment in which the load cell will be installed should also be verified. As load cells are subject to force and mass, they cannot be installed in unstable locations. If a load cell is installed in a location where the applied force or mass causes it to sink into the ground, the correct values cannot be measured. An installation site with the sufficient strength must be available. For environments with harsh surroundings such as large temperature fluctuations, be sure to check temperature, dustproofing, waterproofing, and other specifications.
If you need a load cell, contact MinebeaMitsumi an inquire about our extensive product lineup.
Load cells are used in a variety of situations, from familiar home appliances to product research and development sites, and their applications are continuing to grow due to their high level of precision and long service life. There are various types of load cells, and the appropriate model depends on the type of force or mass to be measured—expertise is required for deploying load cells.
MinebeaMitsumi load cells use strain gages with proprietary design and development for outstanding long-term stability, and an extensive lineup of load cells is available, ranging from small, low-capacity scales to high-capacity industrial load cells. MinebeaMitsumi offers advice and suggestions catering to the needs and required measurements of customers. If you are seeking to deploy load cells, don’t hesitate to send us an inquiry.