March 5, 2026 • 9 mins
Scales range from simple machines that weigh your produce to precision instruments that measure anything from molecules to massive cargo -- but they all work on related principles. Learn how different types of scales work in this episode of BrainStuff, based on this article: https://electronics.howstuffworks.com/gadgets/fitness/digital-scale.htm
See omnystudio.com/listener for privacy information.
Listen
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff,
Lauren Bogelbaum. Here, there's something so commonplace about a weighing
device that it's easy to forget its deeper significance, as
these slightly skewed spring scale in any local produce aisle
reminds us. The scale has long served humans as the
(00:24):
chief arbiter of commerce, the maker or breaker of shipping
budgets and carry on capacity, and the utility player of
the pharmaceutical bench. From the smallest, most fine tuned laboratory
balance to the pit and girder monsters that weigh train
cars and tractor trailers, scales make modern life possible. Scales,
(00:46):
or more specifically, balances weighed heavily on the minds of
ancient builders, inventors, and economic advisors. Too. Small balance weights
dating back to around five to six thousand years ago
provide some of the first hints of mankind evolving grasp
of science and mathematics. The most basic surviving balance from
Egypt predates the Dynastic period, placing its construction at earlier
(01:10):
than three thousand BCE. Like us, the ancient Egyptians applied
scales both in trade and in a saying ores and
alloys balances way an object by matching it against one
or more reference weights. They have a delicate touch and
are still used in laboratories. Scales use somewhat different physical
(01:32):
principles and mechanical components to measure weight in other forces.
Spring scales, for example, measure weight using Hook's law, by
which you can relate in objects weight to the stretching
or compression of a spring made from a given material.
Not all scales use springs, but all do measure weight
using mechanical components, So mechanical and digital scales differ only
(01:57):
in how they display that weight, mechanically like with a
needle on a dial, for example, or electronically alike with
an LED display. In a latter case, the scale employs
an analog to digital converter that translates the continuous readout
data from the scale into discrete digital information, much in
the same way that an MP three encoding scheme digitizes
(02:20):
the waveforms of music. An internal CPU converts the data
into input for a display board, which then shows the
result on a digital screen. Generally speaking, digital scales require
less expertise to use than those with mechanical readouts and
are capable of higher precision and faster processing. Still, the
(02:42):
capabilities of specific devices vary, particularly when the weights are
measured in tons. But let's talk more about those different
mechanical components that let us measure weight with scales. Think
of how a roadside carjack might lift a car via
mechanical adage the leverage of a handle or the inclined
(03:03):
plane of a screw, or how a car mechanic's hoist
might use hydraulic pressure in the same way. Different types
of scales weigh objects using a variety of operational principles,
like hydraulics, pneumatics, or bending beans. Scales come in all shapes, sizes,
and configurations, but the basic component doing the measuring is
(03:25):
nearly always a load cell. A load cell is a
kind of transducer, which is a term for a device
that converts one form of energy into another. Through load cells,
digital scales change mechanical energy the smooshing caused by a
sitting load or the stretching caused by a hanging load,
into an electrical effect. The widely used strain gage, for example,
(03:51):
reads compression or tension as tiny changes in electrical resistance
in what's called a whitstone bridge. Let's break that down
using a compression strain gauge as an example. Okay, Compression
occurs when an applied force reduces an object's volume, but
it can also refer to a more general decrease in
(04:12):
size along one or more dimensions. As it happens, squishing,
an electrically conductive material changes its electrical resistance because longer
and narrower wires are more electrically resistant than shorter and
wider wires. Think of it like water pumping through a pipe.
The longer and narrower the pipe, the harder it will
(04:35):
be to force water through it. Now, different materials experience
different changes in resistance during compression, a quality known as
gauge factor. A gauge factor can also alter in response
to temperature. The go to material for strain measurements is
called constantine alloy. It's usually fifty five percent copper and
(04:56):
forty five percent nickel, and it performs well at the
range temperatures that humans are comfortable at. To detect the
change in resistance caused by weight compression, one or more
strain gages are placed within what's called a whitstone bridge.
A whitstone bridge is an electrical circuit that can detect
an unknown electrical resistance by balancing it against known resistances
(05:19):
elsewhere in the circuit. In a sense, it's like a
balance scale for electrical resistance. The weight of the resistance
on one side tells you the unknown weight of the
resistance on the other. Strain gauges are the most widely
used type of load cell, but they're not the only one.
After all, research, industry, and commerce require the capacity to
(05:42):
measure weights under a seemingly limitless variety of environmental conditions
and space constraints, while also controlling for possible errors. Industries
that require greater safety and sterility often turn into pneumatic
load cells, which derive the weight of an object by
measuring the air pressure necessary to balance it. These blowhards
(06:04):
work well in the food industry and at hazardous sites
because they don't contain fluids that might seep, drip, or
spurt into the environment. Pneumatic cells can have a wide
range of weights with high accuracy, but they require a clean,
dry atmosphere and tend to take their sweet time responding
Hydraulic load cells, which measure load as a change in
(06:26):
fluid pressure are commonly found weighing tanks, bins, and hoppers.
Because they function without electricity, Hydraulic cells work well in
out of the way locals where power is a ify prospect.
They're pricey and complicated, but rugged they can handle million
pound loads. Load cells also come in all kinds of
(06:49):
different sizes, shapes, configurations, and materials, so that you can
use scales in different environments for different jobs. If you
need to take measurements in a wet environment, you can
opt for a hermetically sealed canister cell. If you're in
a facility concerned with height clearance issues, you can use
a thinner bending beam cell. And if you're expecting to
(07:11):
deal with extraneous forces affecting the load cell, say you're
using scales in a moving vehicle, in deep water or
on an aircraft, an s beam load cell that uses
a zigzag design can help control for that. Measuring force
is as fraught with technical troubles as any precision measurement,
which is no minor matter when one considers that piles
(07:33):
of money, and more importantly, human lives can rest on
the difference of a few grams. Researchers develop all kinds
of technologies to help make scales dependable in real world circumstances.
No matter the well scale, these devices could range from
being accurate in laboratory settings to highway weight enforcement and beyond.
(07:56):
On the larger end, scales employ levers to convert extra
large forces into manageable ones. Thus, the load cells in
some large truck scales only need to be able to
measure a fraction of the total weight, and thus can
easily handle between fifty to one hundred thousand pounds, which
is around twenty five to forty five thousand kilos, which
(08:17):
is a lot either way. And remember how Hook's law
helps you more or less accurately weigh your fruit and
vegetables on the spring scale at the grocery store. It
also underlies the operation of one of the smallest force
measuring devices in the world, the atomic force microscope, used
in biochemistry, biology, and materials engineering. Such microscopes use a
(08:41):
micron scale silicon or silicon nitride cantilever, which is a
spring like beam supported only on one side to detect
nano Neewton and peak Newton tugs forces on the scale
of intermolecular attractions. Today's episode is based on the article
(09:03):
how digital scales work on HowStuffWorks dot Com, written by
Nicholas Jerbis. Brain Stuff is production of by Heart Radio
in partnership with HowStuffWorks dot Com and is produced by
Tyler Klang. For more podcasts from my heart Radio, visit
the iHeartRadio app, Apple Podcasts, or wherever you listen to
your favorite shows.
Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff,
Lauren Bogelbaum. Here, there's something so commonplace about a weighing
device that it's easy to forget its deeper significance, as
these slightly skewed spring scale in any local produce aisle
reminds us. The scale has long served humans as the
(00:24):
chief arbiter of commerce, the maker or breaker of shipping
budgets and carry on capacity, and the utility player of
the pharmaceutical bench. From the smallest, most fine tuned laboratory
balance to the pit and girder monsters that weigh train
cars and tractor trailers, scales make modern life possible. Scales,
(00:46):
or more specifically, balances weighed heavily on the minds of
ancient builders, inventors, and economic advisors. Too. Small balance weights
dating back to around five to six thousand years ago
provide some of the first hints of mankind evolving grasp
of science and mathematics. The most basic surviving balance from
Egypt predates the Dynastic period, placing its construction at earlier
(01:10):
than three thousand BCE. Like us, the ancient Egyptians applied
scales both in trade and in a saying ores and
alloys balances way an object by matching it against one
or more reference weights. They have a delicate touch and
are still used in laboratories. Scales use somewhat different physical
(01:32):
principles and mechanical components to measure weight in other forces.
Spring scales, for example, measure weight using Hook's law, by
which you can relate in objects weight to the stretching
or compression of a spring made from a given material.
Not all scales use springs, but all do measure weight
using mechanical components, So mechanical and digital scales differ only
(01:57):
in how they display that weight, mechanically like with a
needle on a dial, for example, or electronically alike with
an LED display. In a latter case, the scale employs
an analog to digital converter that translates the continuous readout
data from the scale into discrete digital information, much in
the same way that an MP three encoding scheme digitizes
(02:20):
the waveforms of music. An internal CPU converts the data
into input for a display board, which then shows the
result on a digital screen. Generally speaking, digital scales require
less expertise to use than those with mechanical readouts and
are capable of higher precision and faster processing. Still, the
(02:42):
capabilities of specific devices vary, particularly when the weights are
measured in tons. But let's talk more about those different
mechanical components that let us measure weight with scales. Think
of how a roadside carjack might lift a car via
mechanical adage the leverage of a handle or the inclined
(03:03):
plane of a screw, or how a car mechanic's hoist
might use hydraulic pressure in the same way. Different types
of scales weigh objects using a variety of operational principles,
like hydraulics, pneumatics, or bending beans. Scales come in all shapes, sizes,
and configurations, but the basic component doing the measuring is
(03:25):
nearly always a load cell. A load cell is a
kind of transducer, which is a term for a device
that converts one form of energy into another. Through load cells,
digital scales change mechanical energy the smooshing caused by a
sitting load or the stretching caused by a hanging load,
into an electrical effect. The widely used strain gage, for example,
(03:51):
reads compression or tension as tiny changes in electrical resistance
in what's called a whitstone bridge. Let's break that down
using a compression strain gauge as an example. Okay, Compression
occurs when an applied force reduces an object's volume, but
it can also refer to a more general decrease in
(04:12):
size along one or more dimensions. As it happens, squishing,
an electrically conductive material changes its electrical resistance because longer
and narrower wires are more electrically resistant than shorter and
wider wires. Think of it like water pumping through a pipe.
The longer and narrower the pipe, the harder it will
(04:35):
be to force water through it. Now, different materials experience
different changes in resistance during compression, a quality known as
gauge factor. A gauge factor can also alter in response
to temperature. The go to material for strain measurements is
called constantine alloy. It's usually fifty five percent copper and
(04:56):
forty five percent nickel, and it performs well at the
range temperatures that humans are comfortable at. To detect the
change in resistance caused by weight compression, one or more
strain gages are placed within what's called a whitstone bridge.
A whitstone bridge is an electrical circuit that can detect
an unknown electrical resistance by balancing it against known resistances
(05:19):
elsewhere in the circuit. In a sense, it's like a
balance scale for electrical resistance. The weight of the resistance
on one side tells you the unknown weight of the
resistance on the other. Strain gauges are the most widely
used type of load cell, but they're not the only one.
After all, research, industry, and commerce require the capacity to
(05:42):
measure weights under a seemingly limitless variety of environmental conditions
and space constraints, while also controlling for possible errors. Industries
that require greater safety and sterility often turn into pneumatic
load cells, which derive the weight of an object by
measuring the air pressure necessary to balance it. These blowhards
(06:04):
work well in the food industry and at hazardous sites
because they don't contain fluids that might seep, drip, or
spurt into the environment. Pneumatic cells can have a wide
range of weights with high accuracy, but they require a clean,
dry atmosphere and tend to take their sweet time responding
Hydraulic load cells, which measure load as a change in
(06:26):
fluid pressure are commonly found weighing tanks, bins, and hoppers.
Because they function without electricity, Hydraulic cells work well in
out of the way locals where power is a ify prospect.
They're pricey and complicated, but rugged they can handle million
pound loads. Load cells also come in all kinds of
(06:49):
different sizes, shapes, configurations, and materials, so that you can
use scales in different environments for different jobs. If you
need to take measurements in a wet environment, you can
opt for a hermetically sealed canister cell. If you're in
a facility concerned with height clearance issues, you can use
a thinner bending beam cell. And if you're expecting to
(07:11):
deal with extraneous forces affecting the load cell, say you're
using scales in a moving vehicle, in deep water or
on an aircraft, an s beam load cell that uses
a zigzag design can help control for that. Measuring force
is as fraught with technical troubles as any precision measurement,
which is no minor matter when one considers that piles
(07:33):
of money, and more importantly, human lives can rest on
the difference of a few grams. Researchers develop all kinds
of technologies to help make scales dependable in real world circumstances.
No matter the well scale, these devices could range from
being accurate in laboratory settings to highway weight enforcement and beyond.
(07:56):
On the larger end, scales employ levers to convert extra
large forces into manageable ones. Thus, the load cells in
some large truck scales only need to be able to
measure a fraction of the total weight, and thus can
easily handle between fifty to one hundred thousand pounds, which
is around twenty five to forty five thousand kilos, which
(08:17):
is a lot either way. And remember how Hook's law
helps you more or less accurately weigh your fruit and
vegetables on the spring scale at the grocery store. It
also underlies the operation of one of the smallest force
measuring devices in the world, the atomic force microscope, used
in biochemistry, biology, and materials engineering. Such microscopes use a
(08:41):
micron scale silicon or silicon nitride cantilever, which is a
spring like beam supported only on one side to detect
nano Neewton and peak Newton tugs forces on the scale
of intermolecular attractions. Today's episode is based on the article
(09:03):
how digital scales work on HowStuffWorks dot Com, written by
Nicholas Jerbis. Brain Stuff is production of by Heart Radio
in partnership with HowStuffWorks dot Com and is produced by
Tyler Klang. For more podcasts from my heart Radio, visit
the iHeartRadio app, Apple Podcasts, or wherever you listen to
your favorite shows.
BrainStuff News
Host
Lauren Vogelbaum
Popular Podcasts
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations. Follow now to get the latest episodes of Dateline NBC completely free, or subscribe to Dateline Premium for ad-free listening and exclusive bonus content: DatelinePremium.com
Fudd Around And Find Out
UConn basketball star Azzi Fudd brings her championship swag to iHeart Women’s Sports with Fudd Around and Find Out, a weekly podcast that takes fans along for the ride as Azzi spends her final year of college trying to reclaim the National Championship and prepare to be a first round WNBA draft pick. Ever wonder what it’s like to be a world-class athlete in the public spotlight while still managing schoolwork, friendships and family time? It’s time to Fudd Around and Find Out!