- Define Load Cell
- How does a Load Cell work?
- How does a Resistive Load cell work?
- Wheatstone bridge Circuit
- What are the benefits of Strain Gauge-based Load Cells?
- What are the disadvantages of Strain Gauge-based Load Cells?
- What are the types of Load Cells?
- Frequently asked Questions
Define Load Cell
A load cell is a kind of force sensor based on a strain gauge in which force transducers employ piezo-resistive force detectors. These force sensors detect the force directly Instead of associating the force with the deformation in a strain gauge.
How does a Load Cell work?
A load cell is a force transducer that produces a measured electrical output signal such as tension, compression, pressure, or torque into a quantitative electrical output signal that can be evaluated and controlled.
The electrical signal changes in accordance with the force applied to the load cell.
Resistive Load Cells
- Resistive load cells work on the piezo-resistivity concept.
- As a load/force/stress is applied to the sensing element, its resistance varies.
- When an input voltage is provided, this change in resistance causes a change in output voltage.
Capacitive Load Cells
- Capacitive load cells work on the basis of capacitance change, which refers to a system’s capacity for storing a certain charge level when a voltage is added to it.
- The capacitance of common parallel plate capacitors is directly related to the rate of plate overlap and the dielectric constant between the plates and is inversely proportional to their separation.
How does a Resistive Load cell work?
- Load cells operate on the strain gauge idea.
- A bending beam with a strain gauge is the most basic sort of load cell.
- The electrical resistance of a metal foil strain gauge fluctuates with applied force.
- Force, pressure, tension, compression, torque, weight, and so on are converted (or transduced) into a change in electrical resistance, which may then be measured.
- The force sensor’s building piece is a metal foil strain gauge.
- One of the interesting uses of this technology is weight measuring through a strain gauge bridge.
- A strain gauge (SG) fitted on the spring element converts this strain (positive or negative) into an electrical output.
- Strain gauges are conductors of electricity that are zig-zagged affixed to a film.
- When this film is stretched, it stretches and extends, just like the conductors.
- When stroked, it contracts and then becomes shorter.
- The resistance in the electrical conductors varies because of the structural change.
- Based on this concept, the strain applied in the load cell may be measured, as strain gauge resistance increases with applied strain and decreases with contraction.
- We apply a Wheatstone bridge circuit in order to translate the strain/resistance change into a voltage proportional to the load.
- The sensor body often is composed of aluminum or stainless steel, which provides the sensor with two essential characteristics: (1) toughness to bear large loads and (2) flexibility to bend slightly and return to its original shape when the force is released.
Wheatstone bridge Circuit
- The four strain gauges are linked together in a Wheatstone Bridge structure, having four individual resistors coupled as illustrated in the Wheatstone Bridge Network.
- An activation voltage – normally 10V – is delivered to one pair of corners, and the voltage differential between the other two corners is determined.
- When the four resistors are closely matched in value, the voltage output is zero or very near zero when no load is applied.
- That is why it is called a balanced bridge circuit.
- When a force is applied to the metallic element to which the strain gauges are mounted, the ensuing strain causes a change in resistance in one (or more) of the resistors.
What are the benefits of Strain Gauge-based Load Cells?
- Accuracy is high
- Robust Construction made of Stainless steel or Aluminium
- Performance is high in rigorous conditions
- Better lifespan
What are the disadvantages of Strain Gauge-based Load Cells?
- Since extremely reactive or corrosive substances might destroy the gauge material, strain gauge load cells cannot be utilised for the pressure measurement of certain types of substances.
- The signal that is produced by the gauge is on the order of millivolts, which means that it needs to be amplified in order to be displayed on the output.
- It is not possible to measure very high loads with this instrument.
What are the types of Load Cells?
1. In-Line Load Cell
- Generally, In-line force transducers are force sensors with male threads.
- This type of load force transducer is appropriate for both pushing and pulling forces.
- In-line sensors enable extreme precision and durability while demanding little mounting gap.
- They are suitable for endurance testing, press-in force measurement, and force measurement detectors for gym training equipment.
- Micro load cells are also available in smaller forms such as micro force sensors, miniature load cells, miniature force sensors, or milli-gram load cells.
2. Column Load Cell
- Column Load Cells, termed Canister Load Cells.
- These load cells are intended for powerful compression tests, such as CNC Machine Vise Clamping Force Tests.
- These devices are intended to endure and feature capacities ranging from 2,000 to 30,000 lbs.
- Small Load Cell Canister series for applications where space is limited.
3. Load Button
- The compressive stress is exerted on a single flat, raised surface (referred to as a button) on these force transducers.
- The low profile load cell design is the load buttons. Regardless of their tiny size, they are known for their durability and are used in exhaustion applications.
- Miniature modes, like LLB-130 subminiature load cell load button, are crucial in most industrial applications.
- Load buttons are used in the evaluation of rolling element-bearing loads.
4. S Beam Load Cell
- The S Beam Load Cell, commonly referred to as the Z Beam Sensor or the S Type load cell,
- This is a tension and compression load cell with female threads for installation.
- This force sensor type is excellent for in-line processing and automated control feedback applications due to its high accuracy and narrow beam load cell, and compact profile.
- In fluid flow measurement applications, S Beam Load cells can also be employed as a non-contact flow sensor.
5. Thru Hole Load Cell
- Thru Hole Load Cell is termed a donut load cell or washer load cell.
- A through-hole load cell has a uniform non-threaded inner diameter which is employed to detect compressive forces that necessitate a shaft to travel itself through the center.
- One of the most common applications for this sensor type is to determine bolt loading.
6. Pancake Load Cells
- A pancake load cell, universal load cell, or shearing web load cell has a center drilled hole for measuring tension or compression stresses.
- These force transducers are employed in applications in which high durability, extended service life, or elevated in-line measurements are desired, including material force testing, tank balancing system load cells, or crane load cell activities.
- They are also very resistant to off-axis loads and come in a low-profile pancake load cell design.
7. Rod End Load Cell
- This load sensor design, also known as Actuator Load Cell, contains a single male thread and one female thread for attachment.
- The male and female thread combinations are best suited for uses that require force sensor integration into the actual fixtures.
8.Bending Beam Load Cell
- It has a thin form that makes it suitable for Industrial applications.
- Bending Beam Load Cells are employed in compression to quantify force, surface pressure, and displacement for Industrial applications.
- The Cantilever Load Cell is an excellent choice for limited spaces because of its compact size.
9. Single Point Load Cell
- Shear Beam Load Cell is another name for Single Point Load Cell.
- Side-mounted load cells with such a single-point design, are intended specifically for Industrial applications that demand high accuracy or large bulk operations.
- These strain-gauged force detectors, also referred to as miniature parallelogram sensors or single-point load cells, monitor both compression and tension.
- Side mount load cells, such as those seen in bottle-filling plants, are an approved OEM weight measuring option.
Frequently asked Questions
What is the load cell principle?
A load cell transforms a force, including such tension, compression, pressure, or torque, into a defined and standardized electrical output.
When strain gauges are bonded to an elastic material, the resulting device is called a load cell.
• Strain gauges are bonded to the location on the elastic material that would see the greatest effect from the stress. This ensures that the measurements are as precise as possible. The strain gauge works on this principle, detecting strain through changes in electrical resistance.
What are load cells and their types?
Load cells are a particular kind of sensor that determines force and load.
- In-Line Load Cell
- Column Load Cell
- Load Button
- S Beam Load Cell
- Thru Hole Load Cell
- Pancake Load Cells
- Rod End Load Cell
- Bending Beam Load Cell
- Single Point Load Cell
What is the working principle of strain gauge load cell?
It transforms an input mechanical force, such as a load, weight, tension, compression, or pressure, into another physical variable, in this case, an electrical output signal that can be measured, converted, and standardized. The electrical signal varies proportionately to the force applied to the force sensor.