A load cell is a device that senses an applied physical force and outputs a signal proportional to the force. The document discusses the history and types of load cells, how they work, common materials used, applications, importance of calibration, and future developments including miniaturization. Load cells are essential force and weight measurement tools used across hundreds of industries.

1. Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/
The Essential Guide to Load Cells
The usefulness of load cells cannot be underestimated. These small devices
permeate a whole array of equipment across hundreds of industries. Read
on to find out more about this humble yet essential force and weight meas-
urement tool.
WHAT IS A LOAD CELL?
A load cell is simply a device that senses an applied physical force and
then gives an observable output quantity that is proportional to the applied
force. There are different types of load cells , most of which are; strain gauge
load cell, hydraulic load cell, pneumatic load cell, capacitive load cell etc.
Generally load cells are weight/force measuring devices.
Each load cell has its mode of operation and characteristics, but the most
common is the strain gauge load cell which is basically a transducer. It is a
transducer because it produces a measurable electrical signal whose mag-
nitude is proportional to that applied physical force.
HISTORY OF LOAD CELLS
The load cell which is a load (force and weight) measuring device is used
for various industrial processes, however before its invention there existed
other load weighing instruments dating far back from ancient civilizations
such as the ancient Egyptians.
During the ancient Egyptian civilization around 3500BC, the Egyptians
adopted a tool called “The Equal Arm Balance” . The balance consisted of a
column with a horizontal bar at its top that holds two pans at each end, the

2. bar and the pans are attached to each other by a rope. Below is a picture of
the balance.
Figure 1: Equal Arm Balance
Then 2500 years after this, a form of unequal arm balance called the “steel
yard balance” was invented by the Romans.
It consisted of a scaled metal arm suspended off center from above by a
hook close to the shorter arm and a known weight called a poise that was
attached to the longer arm.
This allowed it to gradually slide until it balanced the load attached to the
shorter arm. The weight of the unknown load is then obtained based on the
position of the poise on the calibrated arm. Below is a picture of a steelyard
balance.
Figure 2: Steel Yard Balance
Moving forward, Leonardo Da Vinci invented a gradual dial scale in the late
15th century and this marked a great milestone in weight measuring tech-
nologies. It was the first automatic balance system that used the position of
the calibrated weights on a mechanical lever to balance and determine an
unknown weight.
In the 16th century, the Roberval scale was made by the French mathema-
tician called Gilles Personne de Roberval.

3. In the 17th century, spring scales were invented and they created a non-
counter weight approach to weight measurement, which is based on Hooke’s
law.
The scale consists of a spring attached at one end, a hook at the other end
to which the object to be weighed is attached and a pointer that moves
along the markings on the body of the scale.
The position of the pointer is proportional to the weight attached to the
hook, that is, the weight attached stretches the internal spring of the device.
The devices mentioned above were the major weight measuring devices
that existed before actual load cells were invented. Pneumatic and hydrau-
lic load cells were the first set of load cell designs to exist before strain
gauge load cells.
The English physicist Sir Charles Wheatstone devised the bridge circuit in
1843, it measured electrical resistances. This circuit formed the basis for
modern load cell circuitry as the arms of the bridge circuit are fixed with
strain gauges. The strain gauge is a bonded wire device that changes its
resistance when it is deformed (stretched/contracted).
Strain gauge load cells are the most common form of load cells due to their
ability to support large load sizes. However Pneumatic and Hydraulic load
cells still find their applications in some certain industries.
The advent of strain gauge load cells then resulted in the invention of what
is called digital scales, which offer better and more precise load measure-
ment values than earlier weight measurement devices.
HOW DO LOAD CELLS WORK?
Load cells use compressive, bending and tensile force actions to indicate
the size of a load. Each type has its basic mode of operation and they are
explained below:
Pneumatic load cells
Its operation depends on air or gas operated under pressure in a confined
space, hence it is a force balance device. The load force to be measured is
applied to the top of the diaphragm, the force then creates a pressure that
causes the air or gas inside the container to escape through the nozzle and
then deflect the pressure gauge.

4. Figure 3: A Simple Pneumatic Load Cell
Figure 4: A model YGXD305 Pneumatic load
cell manufactured by YGX Tech.
Hydraulic load cells
This is quite similar to the pneumatic type, but uses a piston-cylinder ar-
rangement that uses a liquid medium under pressure in a confined space,
this also makes it a force balance device.
The load force to be measured is applied to the piston, this force pushes
the piston downwards and deflects the diaphragm, this deflection then in-
creases the pressure in the liquid medium.
In other words, the increase in pressure is proportional to the size of the
applied force, this change in pressure is then transmitted to the bourdon
tube pressure gauge by the liquid medium. It should be noted that the pres-
sure calibration is in Newton, hence the value indicated on the pressure

5. gauge is a measure of the force applied on the piston.
Figure 5: A Diagram of a Hydraulic Load Cell.
Figure 6: A model F1108 Hydraulic load
cell manufactured by TECSIS
Strain gauge load cells
A strain gauge load cell is a force sensor and also a transducer device. It is
a transducer that senses an applied load (force weight) and then changes it
into an electrical signal output that is proportional to the load.
When a load is placed on the load application point of the load cell, it
causes a deformation in the dimensions of the underlying strain gauge, this
deformation creates changes in its electrical resistance, hence changes in

6. the output electrical voltage. The voltage is then conditioned to give the
proportional value of the load applied.
Figure 7: A Binocular beam load cell
Figure 8: A model 108BS Stainless
Steel Single Point Load Cell manufactured by AnyLoad
WHAT ARE THE DIFFERENT LOAD
CELL TYPES?
There are three major types of load cells, namely:
 Hydraulic load cells
 Pneumatic load cells
 Strain gauge load cells
The strain gauge load cell comes in varieties of designs and shapes, but
they are majorly of three categories; the full bridge strain gauge load cell
(four strain gauge), the half bridge load cell (two strain gauge) and the
quarter bridge load cell (one strain gauge).
Other types of load cells are:

7.  Vibrating wire load cell
 Capacitor load cell
 Piezoelectric load cell
WHAT ARE THE MATERIALS USED
IN COMMERCIAL LOAD CELLS?
The different load cell types are made from different material parts. Alt-
hough the different designs of a particular load cell type have common ma-
terial parts, this section focuses on the material parts of the three common
load cells and they are:
Pneumatic load cells: A pneumatic load cell has the following parts; an
elastic diaphragm attached with a platform surface to which force can be
applied, an air supply regulator, a nozzle and a pressure gauge. Its metal
body parts are made of stainless steel. Figure 3 above shows the basic
parts of a pneumatic load.
Hydraulic load cells: Its main parts are; an elastic diaphragm, a piston
with a loading platform placed on top of the diaphragm, a liquid medium
and a bourdon tube pressure gauge. The metal body parts are always
made from stainless steel. Figure 5 above shows the basic parts of a hy-
draulic load cell.
Strain gauge load cells: The major material in this load cell is the strain
gauge, they are arranged to form the arms of a Wheatstone bridge circuit.
Other components are the spring element, the sealing element and the
casing of the device. The casing and other metallic parts of the load cell are
usually made from stainless steel. Other basic elements that make up a
strain gauge load cell include the spring element, the sealing elements and
the housing that helps to protect the load cell components.
It can be seen that they do have some material parts in common especially
the metallic parts which is manufactured majorly from Stainless steel.
Stainless steel is used by Original Equipment Manufacturers (OEMs) be-
cause of its broad range of properties that enable it to withstand great
physical stress, thermal stress and bear high loading conditions.
WHAT ARE LOAD CELLS USED
FOR?

8. Generally load cells are used for various load bearing and weight/force
measuring applications, hence they are LOAD (FORCE and WEIGHT)
MEASURING DEVICES.
Their ability to sense force, load and weight makes them applicable in vari-
ous diverse industries such as the medical and pharmaceutical industry,
manufacturing industry, automotive industry, research laboratories, agricul-
tural industry, aerospace and defense industry, robotics systems industry,
marine industry, oil and gas industry etc.
They are found in various devices such as weight checkers, weighing
scales, medical devices, platform and industrial scales, filling and sorting
machineries, rolling mill systems etc.
Load cells are used in devices for various processes such as process
weighing, parts counting, medical equipment testing, pile testing, process
control and automation monitoring. They’re also used in wire tension meas-
urement, silo weight measurement and monitoring, automated container fill-
ing, robot tactile sensing and batch weighing.
But that’s not all, also in automotive seat testing, aerospace structural test-
ing, spring testing, impact force testing, bin weighing, measuring of tie-rod
loads, measurement of load of rolling mills in steel works and detection of
remaining amount in gas cylinders, etc.
In summary, a load cell is used to measure load (force and weight), its re-
sultant output which is the output of the load cell can then be used for other
things such as process control and automation.
WHAT IS A STRAIN GAUGE LOAD
CELL?
A strain gauge load cell is one type of load cell, out of the various load cells
that exists. It is a force sensor and also a transducer. It is a transducer that
senses an applied load (force weight) and then changes it into an electrical
signal output that is proportional to the load. The output electrical signal is
very small (in mV/V), hence it has to be conditioned to give an output read-
ing.

9. The conditioning may include amplification, attenuation, excitation, filtering
and isolation. For amplification, normal operational amplifiers are not effi-
cient for the process, hence an instrumentation amplifier is always conven-
tionally used in commercial weighing systems.
The strain gauge load cell is made out of strain gauges that are electrically
connected in a Wheatstone bridge.
The Wheatstone bridge can be of different configurations which are; one
strain gauge (Quarter Bridge), two strain gauges (half bridge) and four
strain gauges (full bridge). Generally, the number of active elements legs in
the Wheatstone bridge determines the kind of bridge configuration.
Figure 9: A full bridge strain circuit
The strain gauge is a bonded resistive foil sensor which is capable of
stretching and contracting, its resistance varies with applied load. The ma-
terial deforms/stretches and contract, they are bonded onto a beam or a
structural member using adhesives. The strain gauges are mounted in ar-
eas that exhibit strain in compression or tension. Most strain gauges are

10. made from a copper-nickel (constantan) alloys, the alloy metal is cut into
zigzag foils to form the strain gauge.
Figure 10: A Strain Gauge.
WHAT IS A TENSION LOAD CELL?
Tension load cells are one of the type of strain gauge load cells and are de-
signed to measure tensile loads. A tensile load constitute a tensile pulling
force, the tensile force is a load that is applied to a material that acts away
from the surface it is applied to. In other words it acts to pull the material or
object apart or stretch the material it is acting on (in this case, the material
being stretched is the strain gauge).
Tension load cells are of great use for wound or unwound processes e.g. in
the production film and ribbons. If the tensile force is too much, the film can
break, rendering it useless and creating a lot of down time as the machine
will need to be re-threaded.
Also if the tensile force is too low when the film is winding, then the rolls are
too loose, leaving them prone to exposure or causing other machines to
jam. Tension load cells are also used for more than just film, spring coils
are also wound with tension load cells to keep the coils from snapping as
the metal is bent.
The types of tension load cells include S-beam load cells, columns, and low
profile, shackle and link type load cells.

11. Figure 11: An STA Series S-Type/S-
Beam Aluminum Load Cell SAE Thread diagram manufactured by
AmCells.
HOW OFTEN SHOULD LOAD
CELLS BE CALIBRATED?
The calibration of load cells is defined as a set of operations carried out to
compare the accuracy of the load cell with the standards. Many interna-
tional standards such as the ISO9000 specify the maximum period be-
tween re-calibration as once every two years and more frequently if the in-
strument deterioration is significant during that period.
However many users perform annual calibration to ensure that measure-
ments are accurate. Some also just compare the current calibration to the
previous calibration so as to determine a more suitable re-calibration pe-
riod.
It should be noted that frequent calibration improves the accuracy and ef-
fectiveness of the load cell. Also proper inspection, maintenance and clean-
ing of the load cell can help overcome some operational issues that might
lead to quick re-calibration.
WHO ARE SOME OF THE MORE
FAMOUS LOAD CELL MANUFAC-
TURERS?
This section provides a comprehensive list of the popular industrial load cell
manufacturers and suppliers. If you are looking forward to obtaining stand-
ard industrial load cells for your weighing system design, here are the pop-
ular load cell original equipment manufacturers (OEMS):
 Amcells

12.  AnyLoad
 Dale
 LW Measurements
 Omega
 Tacuna Systems
WHAT IS THE AVERAGE COST OF
A LOAD CELL?
The cost of load cells varies with the type of load cell and it depends on
several factors such as its rated capacity, its mode of operation, the mate-
rial of construction, the requirements of the weighing system etc.
The price ranges from about $0.2 for mini load cells to thousands of dollars
for load cells with higher rated capacities.
Browse our range for a full range of:
 Load Cells
 Load Cell Accessories
 Readouts and Load Cells Indicators
THE FUTURE OF LOAD CELLS
In the near future, load cells will find more applications in process automa-
tion in various industries.
Load cells will also find more applications in microsystems, hence resulting
into something called Miniaturized Load Cells (MEMS). These load cells will be
produced as Micro Electro Mechanical Systems (MEMS), which are the lat-
est emerging technologies.
MEMS are micro-sized silicon structures etched in the form of beams, dia-
phragms or plates that can function as sensors within a load cell. MEMS
are fabricated using the bulk and surface micromachining. MEMS can then
be mass produced, because thousands of sensor elements can be fabri-
cated on single wafer with integrated supporting circuits. Although millions
of sensors can be mass produced at a very low price (as low as a few dol-
lars), their applications are still limited compared with foil strain gauges.
The advantages of these load cells will be higher precision, they will be
portable and light weight, enough to be embedded inside materials and
even the human body. They can help improve modern medicine and be
useful in automatically controlling surgical robot, miniaturized load cell can

13. be incorporated into strength-training equipment to prevent lifting strain.
Also the use of multiple miniaturized load cells in robotic artificial limbs to
create toes and fingers that can feel pressure and send that data to the
brain so the wearer can respond.
Other Sources
 K. S. K. Singh, “Digital Fuel Indicator in Two Wheelers,” IJSRD – In-
ternational Journal for Scientific Research & Development, vol. 2, no.
12, p. 4, 2015.
 Guide to the measurement of force, published 1998, by the institute
of measurement and control, ISBN 0 904457 28 1
 Load cell troubleshooting, Technical note VPGT-08, 2015.
 Digital Load Cells: A Comparative Review of Performance and Appli-
cation, published 2003 by the Institute Of Measurement and Control,
WP0803.
 A guide to the specification and procurement of industrial process
weighing systems, published 2000 by the Institute of Measurement
and Control publication, ISDN 0 904457 32 X
 British Standard BS EN 30012-1: 1994 Metrological confirmation sys-
tems for measuring equipment.
 W. Boyes, Instrumentation Reference Book, Butterworth-Heinemann,
2009.
Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/