Aside from BMI, you can ask your health provider about the following methods:. The National Heart, Lung and Blood Institute notes that your risk for heart disease and diabetes increases if you are a woman with a waist measurement greater than 35 inches Often used by fitness professionals, calipers are used to literally pinch your skin folds usually around the waist or hips to estimate your body fat.
The accuracy of this method varies. Results may be more or less accurate depending on the expertise of the person taking the measurement. Shop online for body fat calipers.
Often used to measure bone mass for osteoporosis diagnoses, DEXA scans are also reliable methods of body fat measurement and can be more reliable than relying on BMI alone. The scans can be pricey depending on your location and may not be covered by insurance.
There are sensors on either side of the device that measure your body fat as you hold the device in front of you. Shop online for handheld fat measurement devices. This test is based on the buoyancy of your body weight.
Fat floats more easily than muscle. Based on your buoyancy and your weight, the person administering the test can calculate your body fat percentage. Underwater testing is considered to be an accurate tool for measuring body fat. However, it can be difficult to find a center that has the ability to do this type of testing.
The test can also be uncomfortable. Essentially, when any weight is placed on to a scale, the load cell bends slightly, which causes the electrical signal that runs through the load cell to change. This signal change is due to the amount of electrical resistance the bending causes to the strain gauge inside the load cell. The signal is then read by an electronic device, often a digital weight indicator, and transformed into a digital weight value.
The value is then displayed for reading. Some differences between types of scales and how they work is due to the different types of load cells. These include pneumatic, hydraulic, strain gauge as mentioned in the above example and capacitance. Pneumatic load cells deal with air pressure and consist of an elastic diaphragm attached to a platform surface where you place the object to be weighed. The scale works by using pressurised air to balance out the weight of the object, and the amount of air required is therefore used to determine how heavy the object is.
The pressure gauge then converts the reading into an electrical signal. The hydraulic load cell works by using a fluid such as water or oil. Scales with hydraulic load cells work like pneumatic load cells except they use a piston and pressurized liquid rather than air.
Carefully take apart your bathroom scale to see its inner parts. If you prefer, you can also purchase a cheap scale at the store purely for the purpose of scientific investigation. Check out the internal mechanisms to help discover exactly how they work. Have fun investigating a scale from the inside! Did you get it? Test your knowledge. Wonder Words dial weight mass force pound spring vital digital pressure sensor current circuit statistics calculation transducer electronic equivalent measurement Take the Wonder Word Challenge.
Join the Discussion. Julia Mar 16, I love your site and use it in the classroom regularly. This is not ecologically responsible.
I would prefer advice to find some scales that are headed for the trash. Apr 9, Fofo Jan 26, Do you read my mind? Or did visit my house.. Jan 27, Sage G. Jan 25, Jan 22, Jan 20, Jan 21, Jan 14, Wonderopolis all day thx wonderopolis for being so cool wonder.
Wonderopolis your questions are so great for learning my whole class always does 2 of your questions each day! Jan 8, I think most of us know how it work but at least I know a little bit more!
We think so, too, Wonder Friend! They're helpful, too! Thanks, william! Thanks for the advice, sage! That would be helpful! Nicola Jan 8, I think scales are so cool because they measure your exact weight about and there are so many of them. Luis Jan 8, Does every scale have to use a spring? Jadyn Jan 8, Weight works by comparing an object of unknown weight. For example, a customer who needs to take measurements in a wet environment might choose a hermetically sealed canister cell , whereas a facility concerned with clearance issues might opt for a thinner bending beam cell [sources: Mashaney ; Omega ].
Form factors are also chosen for their ability to minimize the effects of extraneous forces. Scales typically measure force along a single direction called the principal axis -- which, in the case of weight, means downward in the direction of gravitational pull. Weighing errors arise mainly from off-axis forces, which act parallel to the load, and from sideloads , which act perpendicular to it [source: Novatech ].
Thanks to their zigzag design, s-beam load cells excel at eliminating sideload [source: Omega ]. Within each of these categories and subcategories, there are sizes, shapes and price ranges to fit just about every need imaginable.
But there's more to scales than just weighing your options. Measuring force is as fraught with technical troubles as any precision measurement -- no minor matter, when one considers that human lives -- and piles of money -- can rest on the difference of a few grams.
Hooke's law isn't just for weighing produce; 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 micron-scale silicon or silicon nitride cantilever a spring-like beam, supported on only one side to detect nanonewton and piconewton tugs -- forces on the scale of intermolecular attractions [sources: Cumpson et al. An old saying goes that a man with one watch knows what time it is, but a man with two watches is never sure.
Scales must contend with a similar conundrum: If you weigh the same object twice, do you get the same result? How about on different days, under changing weather conditions? If so, can the scale remain consistent despite wear and tear?
These factors -- respectively known as repeatability , reproducibility and adjustment -- are all important, but a prospective buyer must also consider more basic questions, such as the scale's weight range , including its minimum and maximum capacity [source: AWS ].
Then again, those statistics matter little if a device lacks the necessary accuracy and precision for the job. Although the two terms are often misused as synonyms, they're not interchangeable: Accuracy describes how closely an instrument measures an actual or expected value, whereas precision refers to how granular or exact that measurement is. A speed gun that clocks a Scales usually express accuracy as a percentage of full scale FS -- the total calibrated range a device can measure.
Alternatively, error can be expressed as percentage of actual reading AR : For an object weighing pounds on such a scale, a 2 percent AR would mean an error of 2 pounds, whether the scale had a range of 10 pounds or 10, [sources: AWS ; Busch; Plint].
The precision of a scale is similarly variable. By industrial standard, regardless of capacity, scales are split into a maximum of 10, divisions: Hence a 10,pound scale will divvy into one-pound increments, whereas a ,pound scale will divide into pound increments [sources: AWS ; Crowley ; Mashaney ]. Weighing devices are grouped into categories based on these divisions see sidebar. With this in mind, always try to select a scale that is has a high enough capacity to handle what you are measuring, but not much higher.
This will ensure you get the most precision possible, pound for pound. One of the joys of writing for HowStuffWorks. The deft engineering and intricately milled parts that go into these items are, alone, enough to inspire any technophile. Look beyond the appurtenances and appliances to the heart of any device -- particularly one used for measurement -- and you find something even more wondrous: a physical law, ingeniously harnessed to an array of specific and useful tools.
Nowhere is this truer than in scales. In this article alone, I encountered Hooke's law for springs; Pascal's law for fluid pressure; Boyle's Law , Charles' law and Gay-Lussac's law describing the behavior of gases; and Ohm's law for electrical resistance -- and that's to say nothing of the various unnamed laws governing stress and strain.
So the next time you encounter some politician who wants to cut science education in the name of balancing the budget, it might be worth reflecting that our most enduring fiscal facilitators, scales, are made possible by a centuries-old march of scientific discovery.
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