Monday, December 11, 2017
 Article written by Noah Lam

Weighing Scales 101

You step on a scale, the dial points to a number, you slide a little weight on a balance or a digital display reveals your weight. Then you step off and decide what to do next, but how do these scales work?

As Archimedes once said “Give me a place to stand and I will move the Earth.” This is the premise behind a scale. Original scales uses a beam that sits on a pivot point which becomes a fulcrum. This type of scale is also known as a center beam scale. A combination of reference weights would be hung on one side of the beam and on the other end would be the object to be weighed. When the beam is level, you would count the reference weight to determine the results.

The upright beam scales you see in your doctor’s office is a off-center scale, which is similar to the center beam scale. These scales can use smaller reference weights because the fulcrum position of the beam in relation to the weights and the force imposed on the plate. These scales are known as physician scales or a balance beam.

At home, most usually have a mechanical dial scale, which uses levers connected to a plate with a spring. As a weight is placed on the plate, a spring stretches and a pivot point translates the up and down force to a side motion. This side motion is used to create the rotational motion that you see on the dial of the scale. These type of scales are typically found in a bathroom scale.

Today, digital scales are becoming more prominent. Digital scales uses load cell technology that incorporates electro-mechanical transducers that translates the weight into an electrical voltage. The difference in voltage can be measured and then the results are shown on an LED or LCD display. Most digital scales use batteries, while others need to be plugged in. Some models include a calculator to measure your Body Mass Index or probes to measure body fat percentage.

Body Mass Index is the measurement of body fat based on height and weight. A body mass index of less than 18.5 is considered to be underweight, 18.5 to 24.9 is considered normal, 25-29.9 is Overweight, and Over 30 is Obese. To calculate your Body Mass Index, multiply 703 with your weight in pounds then divide by your height in inches and divide again by your height.

All scales have a weight capacity, some are as small as a kitchen scale measuring grams to scales big enough to measure a truck. Exceeding the capacity of the scale will damage it.

Detecto and Health-o-meter both have been leaders in the healthcare industries with the ever popular physician scales that we always see in the doctor’s office. Infant scales are designed to measure small babies. Chair scales are for those who can not stand. Wheelchair scales are unique since they need to accommodate the wheelchair. Some use ramps for each side of the wheels, and other types use a platform to measure weight.