Scales have been used since prehistoric times to determine the weight of objects, with various types of scales developed over time. The need for consistent business practices led to the development of standard weights and measures, with governments creating regulations and agencies responsible for inspecting and certifying scales. Calibration is required to ensure accuracy, with various techniques and naming systems developed over time. In the 20th century, digital scales were developed using electronics, making them portable, durable, and easy to calibrate. Weight and mass are the same on Earth due to gravity, but on other planets, an object’s weight will vary depending on the planet’s gravity.
A scale is any device used to determine the weight of an object; normally includes a scale that indicates weight or compares the object to known calibrated weights. Scales of many types have existed since prehistoric times and may have been as simple as comparing a purchase item in one hand with a stone in the other. In the 21st century, scales can measure everything from small particles to spacecraft, using technology from complex digital equipment to simple weighing scales used for thousands of years.
Lost to history is any indication of when humans first used stairs. Sales of goods by weight have been common for thousands of years and may have first been achieved by hanging an item on one end of a stick and balancing it against a stone or other object for comparison. Over time, the need for consistent business practices has led to the development of standard weights and measures. The Romans are often credited with developing the scales and terms such as the pound used to describe weight.
On Earth, weight and mass are the same, due to Earth’s gravity. A scale measures the mass of an object or person under the effect of the earth’s gravitational pull, known as single gravity. On other planets with less gravity, an object will weigh less but its mass will not change. In space, objects are called “weightless,” which doesn’t mean they’ve lost mass, just the effects of gravity that can be measured on a scale.
A simple scale used since Roman times is the balance or beam scale. Scales often consist of a horizontal arm or beam supported in the center, with a basket or tray supported at each end. The materials to be weighed are placed on one pan, a reference weight of a known amount is placed on the other pan, and the weight is changed or materials are added or removed until the two are balanced and the beam is horizontal.
In the 19th century, balances were developed using calibrated springs to weigh materials. Objects to be weighed were placed on a flat table attached to a coiled spring mechanism, with a pointer attached to the center of the spring. The weight of the object rotated the mainspring, and the hand indicated the weight on a printed or engraved dial or graph, allowing for direct measurement without the need to add weights or adjust a balance wheel.
With the development of electronics in the 20th century, it became possible to produce a scale with minimal moving parts. A digital force gauge could be attached to the underside of the weighing table and an electronic signal sent to processing equipment which could read the weight directly. These digital scales were portable, durable, and easy to calibrate. Many developed countries in the 20th century weighed commercial road trucks, both to evaluate trucking companies for road taxes and to prevent overweight trucks that were unsafe and damaged roads.
The key to good weight measurement is knowing that the scale is accurate. Calibration is required on a regular basis and since historical times various companies have invented a variety of calibration techniques, naming systems and regulations. Different countries may have used different weight systems, but it became apparent that standard calibrated weights were needed so that all scales would be similarly adjusted.
Over time, governments began creating standard weights and measures for commercial goods, both to prevent fraud and to provide a basis for taxation. Many countries in the 21st century had agencies responsible for inspecting and certifying scales used for the sale of a wide variety of goods. Calibrated weights were carefully manufactured, maintained and cross-checked so that all scales were consistent in their measurements.
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