Scales have a long history of becoming increasingly accurate measurements of weight. Ancient scales used basic balances and known weights to measure, while modern scales use precise materials and electronic components. Triple-beam balances improved on simple balances by using smaller weights closer to the fulcrum. Analog spring scales then allowed measurement against a gauge. Today, digital scales use load cells and strain gauges in an analog-to-digital converter to provide highly precise measurements for industries. The most accurate are ultra precision scales using surface acoustic wave transducers to achieve resolutions of 1 part in 100,000.

1. The History
of Scales

2. The History of Scales
If you were to travel back in time and show an ancient
street merchant a digital weighing scale, he would have no
idea what to do with it. Yet over the entire course of history,
scales have been just as important to the economy as they
are today, which is why people have always strived—and
continue to strive—for more accurate measurements.

3. Ancient Measurements: Distance
Before standardized equipment, many measurements were
based on parts of the body, such as a hand or foot—hence
the American “feet.” These measurements became more
accurate when standard rulers were introduced. A known,
reproducible standard would then serve a specific
geographic area.

4. Ancient Measurements: Distance
Later, agreements were made to produce a standard metal
bar with two marks that was very carefully produced. The
distance was designed to represent a fraction of one ten-
millionth of the distance from the equator to the north pole.

5. Ancient Measurements: Distance
The bar was made from a very stable material called
platinum iridium and was stored in an area where
environmental conditions like temperature were kept as
constant as possible. Copies of this bar could be
reproduced and sent to different locations.

6. Ancient Measurements: Distance
More recently, however, the definition of a meter was
changed to be even more accurate. It was defined as the
distance that light would travel in a particular, very small
fraction of a second. This distance is very standard and can
be reproduced anywhere.

7. Ancient Measurements: Time
Similarly, the measurement of time has also become much
more accurate over the course of history. The earliest
measurements were based on the length of a day, or the
amount of time between sunrise and sunset.

8. Ancient Measurements: Time
More accuracy was obtained with the invention of the
sundial, which could divide a day into a number of parts.
Special candles were built that were meant to burn at a
steady rate, which provided a more accurate means of
telling time.

9. Ancient Measurements: Time
Hourglasses, water clocks and then pendulum clocks
provided significant improvements. Much more recent
clocks utilized electronic devices such as a tuning fork, a
quartz crystal and then atomic clocks for vast
improvements.

10. Ancient Measurements: Weight
Weight measurements and scales have followed a very
similar path. Some of the earliest examples of weight
measurement were a simple rod that was suspended by a
string in the middle. A pan was attached to each end and
the product that needed to be placed in one pan, while
stones representing a known weight were added to the
other until the rod was balanced.

11. Ancient Measurements: Weight
In fact, many of our earliest known written histories dwell on
the requirement for society to use “true weights.”

12. Ancient Measurements: Weight
The most ancient scales were rudimentary balances
consisting of a lever with two pans suspended at equal
distances from the fulcrum. When an item—such as a sack
of gold coins—needed to be weighed, it would be placed in
one of the pans. Known weights would then be added to
and taken away from the opposite pan until the lever was
perfectly balanced in a horizontal position. By calculating
the total of the known weights, it was possible to determine
the weight of the object in the other pan.

13. Ancient Measurements: Weight
This system and similar variations were used until the late
1700s when new weighing technologies were invented.
However, these inventions were not as accurate as the
electronic systems that were designed and perfected in the
20th
and 21st
centuries

14. The Triple-Beam Balance
More recently, the much more practical and intricate triple-
beam balance was created. This device also uses a lever
system in which the force on one side of the fulcrum is
balanced with the force on the other side of the fulcrum.

15. The Triple-Beam Balance
Unlike the original simple balance, however, the triple-
beam balance takes advantage of the concept that a mass
further away from the fulcrum of the lever creates more
force on the lever than a mass that is closer to the lever.

16. The Triple-Beam Balance
So rather than requiring equivalent weights on both sides of
the lever to put the balance in equilibrium, the triple-beam
balance is used by moving smaller weights closer and
further from the fulcrum to balance out the weight of the
object on the opposite side of the lever.

17. The Triple-Beam Balance
It’s likely that you’ve used this type of scale in your middle
or high school physical science class.

18. Analog Scales
The next innovation was an analog scale called a spring
scale, which relies on the concept that a force placed on a
spring will stretch the spring a known distance its “spring
constant” is known.

19. Analog Scales
An indicator on the spring will move up and down a set
distance against a gauge, which is marked with various
weight measurements. When the force of the spring and
the force of the object being weighed are in equilibrium, the
correct weight can be read.

20. Analog Scales
The most common type of spring scale is the bathroom
scale, which combines the force of four levers coming from
each corner of the scale to stretch a spring and spin a
gauge.

21. Analog Scales in Today’s World
Analog scales are a perfect solution when a weight
measurement doesn’t have to be very precise. They can
determine a person’s body weight to within a pound or
measure a serving of meat to within a few ounces.

22. Analog Scales in Today’s World
However, they aren’t accurate enough for many industrial
processes that require a higher level of precision. While a
spring scale may have a resolution of 1 part in 100,
industrial processes commonly require resolutions of 1 part
in 5,000 or higher.

23. Digital Scales
Since their inception, digital scales have taken over as the
most precise measuring devices and are by far the mostly
widely used in industry. These electronic scales include
bench, platform, floor, drum and cylinder scales.

24. Digital Scales
The weight transducer used in digital industrial scales is
called a strain gauge load cell. The load cell is a block of
metal that is shaped in a way so that it bends, much like a
spring, in a very predictable manner when a force acts
upon it. Additionally, like a spring, when the force is
removed, the load cell moves back to its original
configuration.

25. Digital Scales
Attached to the load cell are several strain gauges. These
resistors are made up of folds of flat metal. When the load
cell bends and the strain gages are stretched, their
resistance changes proportional to the amount of force
acting on the load cell. The output signal from the strain
gages is sent to an ADC (analog-to-digital converter), which
outputs a final weight reading.

26. Ultra Precision Scales
Ordinary strain gauge digital scales have resolutions of
about 1 part in 5,000 and an accuracy of about 1/10 of 1%.
However, this still isn’t as precise as some industries
require, which is why we’ve developed a new weighing
technology called Surface Acoustic Wave (SAW) and
designed a new line of Ultra Precision industrial scales.

27. Ultra Precision Scales
These industrial scales use two semiconductor substrates
and SAW transducers. When weight is applied to the scale,
it creates a bulk wave that travels between the transducers.
The frequency of oscillation of these devices is directly
proportional to the weight on the scale platform. By
measuring this digitally, we’re able to offer resolutions of 1
part in 100,000 and accuracy of 1/100 of 1%.

28. Ultra Precision Scales
These scales are particularly useful in situations where high
precision is necessary, such as check weighing, small parts
counting, accurate filling, flow rate monitoring and polymer
production. The pharmaceutical, chemical, paint and many
other industries rely on this Ultra Precision technology.

29. Ultra Precision Scales
Arlyn Scales’ history is one of advancement and innovation,
and so is our future. We’re currently working on several
projects that will allow us to upgrade the accuracy of our
scales even further, improve the interface of our digital
indicators and advance system communication through our
SAW technology, Android interfaces and Cloud computing
systems.

30. The History of Scales
To learn more about the innovations happening at Arlyn
Scales or to discuss your unique weighing needs, contact
us today!