Keep in mind, though, that the accuracy of this method depends on the skill of the technician using the calipers, Michael says. By Leslie Truex Updated August 18, Leslie Truex. Leslie Truex has been telecommuting and freelancing since She has been an Aerobics and Fitness Association of America certified fitness instructor since Video of the Day. Healthy Body Fat Percentages Body fat percentage is the amount of fat in your body compared to all the other components of the body.
Are Body Fat Scales Reliable? Other Ways to Measure Body Fat. Underwater Weighing. You'll only find this method in specialized facilities, and it can cost a pretty penny.
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. When an object is placed on the platform, the piston applies increased pressure to the contained liquid which is proportional to the applied weight.
After calibrating the pressure, you are able to take an accurate measure of the weight and use the pressure reading as an analogue gauge or convert it to an electric signal. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.
Mobile Newsletter chat subscribe. Bath and Laundry. Inside a Bathroom Scale. Yet this second technology has some innate flaws and a high cost that make it a less than ideal solution. This design has become the industry standard over the last half a century. When the shape of the resistor in this case the strain gage is allowed to change, the resistance value also changes.
Strain gages are generally manufactured from a flat foil material, shaped into a long serpentine path and carefully bonded to a spring element called a load cell. The load cell bends when weight is applied to the platform, which changes the shape of the gage and consequently increases its resistance value. This bridge is an electrical circuit that measures the unknown electrical resistance of the gage and turns it into a voltage output.
When the weight was removed, it would return to its exact starting position. But a spring with unlimited bending potential will eventually undergo plastic deformation and lose the characteristics that make it a good spring. Kind of like the Slinky you handled too roughly as a kid that never returned to its perfect coil or worked how it was supposed to.
In an ideal world, a change in length would be the only thing that caused the resistance of a gage to change. But resistors exist in the real world where many other influences come into play. Fluctuating temperatures are the largest cause of error, but microscopic abnormalities in the gage material and simple age can also introduce errors. Quality manufacturers bond strain gages to the load cell using a very thin, smooth layer of glue.
Yet even the most careful application is never perfect simply because glue has no spring characteristics and restricts those of the load cell. This means that the exact bending of the load cell can never be transmitted to the gage. The conversion from analog to digital signal can also introduce errors into the final measurement.
That makes them easy to construct and maintain.
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