How a load cell works

What is a load cell, what are the different types of force sensors and how do they work in force measurement? Get to know the functionalities and capabilities of various load cells, also known as force transducers, in this comprehensive guide.

Load Sensor manufactured in US by FUTEK Advanced Sensor Technology (FUTEK), a leading load cell manufacturer producing a huge selection of Force Transducers, utilizing one of the most advanced technologies in the Sensor Industry: Metal foil strain gauge technology. A Force Sensor is defined as a transducer that converts an input mechanical load, weight, tension, compression or pressure into an electrical output signal (load cell definition). Force Sensors are also commonly known as Force Transducer. There are several types of load cells based on size, geometry and capacity. 


What is a Load Cell, Force Sensor or Force Transducer?

By definition, load cell (or loadcell or load cell monitoring system) is a type of transducer, specifically a force transducer. It converts an input mechanical force such as load, weight (aka weight sensors), tension, compression or pressure (aka pressure sensors for pressure measurement) into another physical variable, in this case, into an electrical output signal that can be measured, converted and standardized. As the force applied to the force sensor increases, the electrical signal changes proportionally.

Load moniatoring systems became an essential element in many industries from Automotive, High precision manufacturing, Aerospace & Defense, Industrial Automation, Medical & Pharmaceuticals and Robotics where reliable and high precision load measurement is paramount (i.e. medical load cell). Most recently, with the advancements in Collaborative Robots (Cobots) and Surgical Robotics, many novel force measurement applications are emerging, such as miniature medical sensors for robotic surgery.

LCM100 Miniature In Line Load Cell

LTH300 Donut Thru Hole Load Cell - Force Washer



How does a load cell work?

Firstly, we need to understand the underlying physics and material science behind the load cell working principle, which is the strain gauge (sometimes referred to as Strain gage). Metal foil strain gage is a material whose electrical resistance varies with applied force. In other words, it converts (or transduces) force, pressure, tension, compression, torque, weight, etc… into a change in electrical resistance, which can then be measured. So, metal foil strain gauge is the building block of force sensor working principle. Weight measurement using strain gauge bridge is also one of the comment applications of this technology.

Strain gauges are electrical conductors tightly attached to a film in a zigzag shape. When this film is pulled, it – and the conductors – stretches and elongates. When it is pushed, it is contracted and gets shorter. This change in shape causes the resistance in the electrical conductors to also change. The strain applied in the load cell can be determined based on this principle, as strain gauge resistance increases with applied strain and diminishes with contraction.

load force transducer sensor working principle load cell monitoring system load monitoring systems
Fig 1: Metal Foil Strain gage. Source: ScienceDirect


Structurally, a force sensor (or transducer) is made of a metal body (also called flexure) to which foil strain gauges are bonded. The sensor body is usually made of aluminum or stainless steel, which gives the sensor two important characteristics: (1) provides the sturdiness to withstand high loads and (2) has the elasticity to minimally deform and return to its original shape when the force is removed.

When force (tension or compression) is applied, the metal body acts as a “spring” and is slightly deformed, and unless it is overloaded, it returns to its original shape. As the flexure deforms, the strain gage also changes its shape and consequently its electrical resistance, which creates a differential voltage variation through a Wheatstone Bridge circuit. Thus, the change in voltage is proportional to the physical force applied to the flexure.

Fig. 2: Strain gauge deformation in both tension and compression.



These strain gauges are arranged in what is called a Wheatstone Bridge Circuit (see load cell circuit animated diagram). This means that four strain gages are interconnected as a loop circuit and the measuring grid of the force being measured is aligned accordingly.

The load cell amplifier module (or load cell signal converters) provide regulated excitation voltage to the load cell Wheatstone bridge amplifier and convert the mv/V output signal into another form of signal that is more useful to the user. The signal generated by the strain gage bridge is low strength signal and may not work with other components of the load cell monitoring system, such as PLC, data acquisition modules (DAQ), load cell data logger, computers, or microprocessors. Thus, strain gauge amplifier functions include excitation voltage, noise filtering or attenuation, signal amplification, and output signal conversion (i.e. load cell ADC ).

Furthermore, the change in the strain gauge amplifier voltage output is calibrated to be linearly proportional to the Newtonian force applied to the flexure.

Fig. 3: Strain Gauge Load Cell – Full Bridge Wheatstone Circuit.

An important concept regarding force transducers is load cell sensitivity and accuracy. Force Sensor accuracy can be defined as the smallest amount of force that can be applied to the sensor body required to cause a linear and repeatable variation in the voltage output. The higher the force transducer load cell accuracy, the better, as it can consistently capture very sensible force variations. In applications like high precision factory automation, surgical robotics, aerospace, load cell linearity is paramount in order to accurately feed the PLC or DAQ control system with the accurate force measurement. Some of our Universal Pancake Load Cells presents Nonlinearity of ±0.1% (of Rated Output) and Nonrepeatability of ±0.05% RO.



What are the advantages of strain gage-based load cells?

Metal foil strain gauge load cell sensors (not a draw wire sensor) are the most common technology, given its high accuracy, long term reliability, variety of shapes and sensor geometry and cost-effectiveness when compared to other force measurement technologies. Also, strain gage force measuring sensors are less affected by temperature variations.

  • The highest accuracy which may conform to many standards from Surgical Robotics to Aerospace;
  • Robust Construction made of either high strength Stainless steel or Aluminum;
  • Maintain high performance at the longest possible work life even at the most rigorous conditions. Some load cell designs can go up to billions of fully reversed cycles (lifespan).
  • A plethora of geometries and customized shapes, as well as mounting options for ANY scale ANY-where.
  • A full gamut of selections with capacities ranging from 10 grams to 100,000 pounds.


What are the types of Load Cells?

Although there several technologies to measuring force, we will focus on the most common type of load cell: metal foil strain gauge. Within the types of force sensors, there are a variety of body shapes and geometries, each one catering to distinct applications. Get to know them if you want to buy load cell:

Other unique designs are also available such as the load pin load cells (aka load cell pin), seat belt load cell, and others. 


LLB130 Miniature Load Button

LCA305 Miniature Column Load Cell



How to choose a load cell for your application?

We understand that choosing the right load transducer is a daunting task, as there is no real industry standard on how you go about selecting load cells for sale. There are also some challenges you may encounter, including finding the compatible strain gage amplifier, strain gauge signal conditioner or requiring a custom product that would increase the product’s delivery time.

To help you select your force sensor, FUTEK developed an easy to follow, 5-Steps guide. Here is a glimpse to help you narrow down your choices. Check out our “Important Considerations in Selecting a Load Cell” complete guide for further information.

  • Step 1: Understand your application and what you are measuring. Load sensors are different from industrial pressure sensors (aka pressure transducer) or torque sensors and they are designed to measure tension and compression loads.
  • Step 2: Define the sensor mounting characteristics and its assembly. Do you have static load or is it a dynamic type? Define the mounting type. How will you be mounting this Force Sensor?


In-Line Diagram load cell sizing how to select a load cell load cell monitoring system
In-Line Diagram load cell sizing how to select a load cell load cell monitoring system
In-Line Diagrams
Side Mount Diagram load cell sizing how to select a load cell

Side Mount Diagram load cell sizing how to select a load cell
Side Mount Diagrams


  • Step 3: Define your minimum and maximum capacity requirements. Be sure to select the capacity over the maximum operating load and determine all extraneous load (side loads or off-center loads) and moments prior to selecting the capacity. In some instances, you will require a multi axis load cell such as a 6 axis sensor. One of typical multi axis load cell applications in aerospace is the rocket engine thrust test stand necessary to characterize the rocket engine thrust curves and Isp in static testing conditions.
  • Step 4: Define your size and geometry requirements (width, weight, height, length, etc) and mechanical performance requirements (output, nonlinearity, hysteresis, creep, bridge resistance, resolution, frequency response etc.) Other characteristics to consider include waterproof force sensor (submersible load cell), cryogenic, high temperature, multiple or redundant bridges, and TEDS IEEE1451.4.
  • Step 5: Define the type of output your application requires. Force transducers circuitry output is in mV/V (millivolts per volt). Hence, if your PLC, instrument or DAQ requires analog output (i.e. 4-20ma load cell), digital output or serial communication (i.e. digital load cells output or USB load cell), you will certainly need a load cell amplifier. Some applications require a digital load cell indicator or a handheld display for local load cell readout. Make sure to select the right amplifier as well as calibrate the entire load measurement system (load transducer + signal conditioner). This turnkey solution translates into more compatibility and accuracy of the entire load measurement systems.

 When combined with a draw wire sensor (aka string potentiometer), load cells are the linchpin of modern factory automation.

FUTEK has special types of Universal Signal Conditioner Module that supports a wide range of sensor inputs such as ± 10 VDC, 0-20 mA, ±400 mV/V and TTL encoder pulses type inputs. USB520 USB Universal Signal Conditioner Module can be paired with various sensor types and eliminates the need for external power supply to the sensor and display equipment. The module is supplied by PC power through a USB Cable, providing excitation voltage 5-24 VDC to the sensor and simultaneously 5 VDC for Encoders.

For more details on our 5-Steps Guide, please visit our “How to choose a Load cell” for complete guidelines.

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Multi Axis Sensor, Force, Torquehow-a-load-cell-works
Z540-1 ANSI Certified17025 ISO Certified9001 ISO Certified13485 ISO CertifiedU.S. Manufacturer
Please follow us on linked inPlease follow us on twitterPlease follow us on youtubePlease Email us for additional info
10 Thomas, Irvine,
CA 92618 USA
All other trademarks, service marks and logos used in this website are the property of their respective owners.
© 1998–2023 FUTEK Advanced Sensor Technology, Inc. All rights reserved.