A scale or balance is a device used to measure weight or mass . These are also known as mass scales , weight scales , mass balances , massometers , and weight balances .
82-451: W & T Avery Ltd. (later GEC Avery ) was a British manufacturer of weighing machines . The company was founded in the early 18th century and took the name W & T Avery in 1818. Having been taken over by GEC in 1979 the company was later renamed into GEC-Avery. The company became Avery Berkel in 1993 when GEC acquired the Dutch company Berkel. After the take over by Weigh-Tronix in 2000
164-638: A ( F A ⋅ e A ⊥ ) − b ( F B ⋅ e B ⊥ ) = a F A − b F B , {\displaystyle F_{\theta }=\mathbf {F} _{A}\cdot {\frac {\partial \mathbf {v} _{A}}{\partial {\dot {\theta }}}}-\mathbf {F} _{B}\cdot {\frac {\partial \mathbf {v} _{B}}{\partial {\dot {\theta }}}}=a(\mathbf {F} _{A}\cdot \mathbf {e} _{A}^{\perp })-b(\mathbf {F} _{B}\cdot \mathbf {e} _{B}^{\perp })=aF_{A}-bF_{B},} where F A and F B are components of
246-440: A balance , which compares the torque on the arm due to a sample weight to the torque on the arm due to a standard reference mass using a horizontal lever . Spring scales measure force , which is the tension force of constraint acting on an object, opposing the local force of gravity. They are usually calibrated so that measured force translates to mass at earth's gravity. The object to be weighed can be simply hung from
328-419: A beam or rigid rod pivoted at a fixed hinge , or fulcrum . A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is divided into three types . It is one of the six simple machines identified by Renaissance scientists. A lever amplifies an input force to provide a greater output force, which is said to provide leverage , which
410-421: A load cell instead. A voltage is applied to the device, and the weight causes the current through it to change. The current is converted to a digital number by an analog-to-digital converter , translated by digital logic to the correct units, and displayed on the display. Usually, the device is run by a microprocessor chip. A digital bathroom scale is a scale on the floor which a person stands on. The weight
492-417: A cloud service or an ERP system for real-time monitoring and management of material flow. A pallet jack scale is a device that combines a pallet jack and a weighing scale. It allows you to weigh and move pallets at the same time, saving time and labor. Pallet jack scales are used in various industries, such as manufacturing, logistics, and shipping. Lever A lever is a simple machine consisting of
574-400: A constant gravity or acceleration. Very precise measurements are achieved by ensuring that the balance's fulcrum is essentially friction -free (a knife edge is the traditional solution), by attaching a pointer to the beam which amplifies any deviation from a balance position; and finally by using the lever principle, which allows fractional masses to be applied by movement of
656-504: A foot pedal was used for the earliest horizontal frame loom . In Mesopotamia (modern Iraq) c. 3000 BC , the shadouf , a crane-like device that uses a lever mechanism, was invented. In ancient Egypt , workmen used the lever to move and uplift obelisks weighing more than 100 tons. This is evident from the recesses in the large blocks and the handling bosses which could not be used for any purpose other than for levers. The earliest remaining writings regarding levers date from
738-400: A force to counter the sample being measured and output the result by measuring the force needed to achieve balance. Such a measurement device is called an electromagnetic force restoration sensor. Pendulum type scales do not use springs. These designs use pendulums and operate as a balance that is unaffected by differences in gravity. An example of application of this design are scales made by
820-419: A fulcrum at its center. For highest accuracy, the fulcrum would consist of a sharp V-shaped pivot seated in a shallower V-shaped bearing. To determine the mass of the object, a combination of reference masses was hung on one end of the beam while the object of unknown mass was hung on the other end (see balance and steelyard balance ). For high precision work, such as empirical chemistry, the center beam balance
902-431: A hinge, or pivot, called a fulcrum. The ideal lever does not dissipate or store energy, which means there is no friction in the hinge or bending in the beam. In this case, the power into the lever equals the power out, and the ratio of output to input force is given by the ratio of the distances from the fulcrum to the points of application of these forces. This is known as the law of the lever . The mechanical advantage of
SECTION 10
#1732780725963984-436: A kitchen during cooking. These are usually lightweight and compact. In electronic versions of spring scales, the deflection of a beam supporting the unknown mass is measured using a strain gauge , which is a length-sensitive electrical resistance . The capacity of such devices is only limited by the resistance of the beam to deflection. The results from several supporting locations may be added electronically, so this technique
1066-446: A lever can be determined by considering the balance of moments or torque , T , about the fulcrum. If the distance traveled is greater, then the output force is lessened. T 1 = F 1 a , T 2 = F 2 b {\displaystyle {\begin{aligned}T_{1}&=F_{1}a,\quad \\T_{2}&=F_{2}b\!\end{aligned}}} where F 1
1148-415: A lever is the ratio of output force to input force. M A = F 2 F 1 = a b . {\displaystyle MA={\frac {F_{2}}{F_{1}}}={\frac {a}{b}}.\!} This relationship shows that the mechanical advantage can be computed from ratio of the distances from the fulcrum to where the input and output forces are applied to the lever, assuming
1230-424: A margin of error +/- 7 mg. Many microbalances and ultra-microbalances that weigh fractional gram values are torsion balances. A common fiber type is quartz crystal. A microbalance (also called an ultramicrobalance, or nanobalance) is an instrument capable of making precise measurements of the mass of objects of relatively small mass: on the order of a million parts of a gram and below. An analytical balance
1312-456: A pair of equal-length arms and pivoting in the center of each arm from a central vertical column, creating a parallelogram. From the side of each vertical column a peg extended. To the amazement of observers, no matter where Roberval hung two equal weight along the peg, the scale still balanced. In this sense, the scale was revolutionary: it evolved into the more-commonly encountered form consisting of two pans placed on vertical column located above
1394-410: A personal hand in their development. Even with all the advances in weighing scale design and development, all scales until the seventeenth century AD were variations on the balance scale. The standardization of the weights used – and ensuring traders used the correct weights – was a considerable preoccupation of governments throughout this time. The original form of a balance consisted of a beam with
1476-431: A platform can be floated on a cantilever beam system which brings the proportional force to a noseiron bearing; this pulls on a stilyard rod to transmit the reduced force to a conveniently sized beam. One still sees this design in portable beam balances of 500 kg capacity which are commonly used in harsh environments without electricity, as well as in the lighter duty mechanical bathroom scale (which actually uses
1558-423: A rigid bar connected to a ground frame by a hinged joint called a fulcrum. The lever is operated by applying an input force F A at a point A located by the coordinate vector r A on the bar. The lever then exerts an output force F B at the point B located by r B . The rotation of the lever about the fulcrum P is defined by the rotation angle θ in radians. Let the coordinate vector of
1640-510: A small mass along the measuring arm of the beam, as described above. For greatest accuracy, there needs to be an allowance for the buoyancy in air, whose effect depends on the densities of the masses involved. To reduce the need for large reference masses, an off-center beam can be used. A balance with an off-center beam can be almost as accurate as a scale with a center beam, but the off-center beam requires special reference masses and cannot be intrinsically checked for accuracy by simply swapping
1722-421: A smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single-pan mechanical substitution balances maintain consistent response throughout the useful capacity, which
SECTION 20
#17327807259631804-573: A spring scale, internally). The additional pivots and bearings all reduce the accuracy and complicate calibration; the float system must be corrected for corner errors before the span is corrected by adjusting the balance beam and poise. In 1669 the Frenchman Gilles Personne de Roberval presented a new kind of balance scale to the French Academy of Sciences. This scale consisted of a pair of vertical columns separated by
1886-472: A stand and the outside gears fixed to pans, as well as the "sprocket gear balance" consisting of a bicycle-type chain looped around an odd number of sprockets with the central one fixed and the outermost two free to pivot and attached to a pan. Because it has more moving joints which add friction, the Roberval balance is consistently less accurate than the traditional beam balance, but for many purposes this
1968-426: A two-pan, beam balance) are one of the traditional symbols of justice , as wielded by statues of Lady Justice . This corresponds to the use in a metaphor of matters being "held in the balance". It has its origins in ancient Egypt. Scales also are widely used as a symbol of finance, commerce, or trade, in which they have played a traditional, vital role since ancient times. For instance, balance scales are depicted in
2050-415: A weightless lever and no losses due to friction, flexibility or wear. This remains true even though the "horizontal" distance (perpendicular to the pull of gravity) of both a and b change (diminish) as the lever changes to any position away from the horizontal. Levers are classified by the relative positions of the fulcrum, effort and resistance (or load). It is common to call the input force "effort" and
2132-413: Is mechanical advantage gained in the system, equal to the ratio of the output force to the input force. As such, the lever is a mechanical advantage device , trading off force against movement. The word "lever" entered English around AD 1300 from Old French : levier . This sprang from the stem of the verb lever , meaning "to raise". The verb, in turn, goes back to Latin : levare , itself from
2214-460: Is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance (0.1 mg or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure , which has uniquely designed acrylic airfoils, allows
2296-439: Is a weighing system that is built into a forklift truck. It allows for the weighing of loads while they are being lifted and transported by the forklift. This eliminates the need for separate weighing operations and reduces the time and labor required for material handling operations. Forklift scales are used in various industries, such as manufacturing, logistics, and shipping. Material Handler Scale : A Material Handler Scale
2378-400: Is a weighing system that is integrated into a material handler machine, such as a grapple or a magnet. It allows for the accurate and efficient weighing of materials while they are being moved, unloaded, or loaded. A Material Handler Scale can be used in various industries, such as scrap, recycling, waste, and port and harbor. A Material Handler Scale can also transfer the weighing information to
2460-823: Is achieved and the plates level off, which happens when the masses on the two plates are equal. The perfect scale rests at neutral. A spring scale will make use of a spring of known stiffness to determine mass (or weight). Suspending a certain mass will extend the spring by a certain amount depending on the spring's stiffness (or spring constant ). The heavier the object, the more the spring stretches, as described in Hooke's law . Other types of scales making use of different physical principles also exist. Some scales can be calibrated to read in units of force (weight) such as newtons instead of units of mass such as kilograms . Scales and balances are widely used in commerce, as many products are sold and packaged by mass. The balance scale
2542-423: Is achieved by maintaining a constant load on the balance beam and thus the fulcrum by subtracting mass on the same side of the beam to which the sample is added. Electronic analytical scales measure the force needed to counter the mass being measured rather than using actual masses. As such they must have calibration adjustments made to compensate for gravitational differences. They use an electromagnet to generate
W & T Avery - Misplaced Pages Continue
2624-491: Is compensated for by its usability. The torsion balance is one of the most mechanically accurate of analog balances. Pharmacy schools still teach how to use torsion balances in the U.S. It utilizes pans like a traditional balance that lie on top of a mechanical chamber which bases measurements on the amount of twisting of a wire or fiber inside the chamber. The scale must still use a calibration weight to compare against, and can weigh objects greater than 120 mg and come within
2706-428: Is given by: M A = F B F A = a b . {\displaystyle MA={\frac {F_{B}}{F_{A}}}={\frac {a}{b}}.} This is the law of the lever , which was proven by Archimedes using geometric reasoning. It shows that if the distance a from the fulcrum to where the input force is applied (point A ) is greater than the distance b from fulcrum to where
2788-451: Is shown on an LED or LCD display. The digital electronics may do more than just display weight, it may calculate body fat, BMI , lean mass, muscle mass, and water ratio. Some modern bathroom scales are wirelessly or cellularly connected and have features like smartphone integration, cloud storage, and fitness tracking. They are usually powered by a button cell, or battery of AA or AAA size. Digital kitchen scales are used for weighing food in
2870-524: Is still one of the most accurate technologies available, and is commonly used for calibrating test masses. However, bronze fragments discovered in central Germany and Italy had been used during the Bronze Age as an early form of currency. In the same time period, merchants had used standard weights of equivalent value between 8 and 10.5 grams from Great Britain to Mesopotamia. The balance (also balance scale , beam balance and laboratory balance )
2952-498: Is such a simple device that its usage likely far predates the evidence. What has allowed archaeologists to link artifacts to weighing scales are the stones for determining absolute mass. The balance scale itself was probably used to determine relative mass long before absolute mass. The oldest attested evidence for the existence of weighing scales dates to the Fourth Dynasty of Egypt , with Deben (unit) balance weights, from
3034-470: Is suitable for determining the mass of very heavy objects, such as trucks and rail cars, and is used in a modern weighbridge . These scales are used in the modern bakery , grocery , delicatessen , seafood , meat , produce and other perishable goods departments. Supermarket scales can print labels and receipts, mark mass and count, unit price, total price and in some cases tare . Some modern supermarket scales print an RFID tag that can be used to track
3116-481: Is the generalized coordinate that defines the configuration of the lever, and the generalized force associated with this coordinate is given by F θ = F A ⋅ ∂ v A ∂ θ ˙ − F B ⋅ ∂ v B ∂ θ ˙ =
3198-445: Is the input force to the lever and F 2 is the output force. The distances a and b are the perpendicular distances between the forces and the fulcrum. Since the moments of torque must be balanced, T 1 = T 2 {\displaystyle T_{1}=T_{2}\!} . So, F 1 a = F 2 b {\displaystyle F_{1}a=F_{2}b\!} . The mechanical advantage of
3280-410: Is used to describe a weighing device that is used to measure the mass, force exertion , tension, and resistance of an object without the need of a power supply. Types of mechanical scales include decimal balances , spring scales , hanging scales, triple beam balances , and force gauges . A spring scale measures mass by reporting the distance that a spring deflects under a load. This contrasts to
3362-439: Is used. It is also common in high-capacity applications such as crane scales to use hydraulic force to sense mass. The test force is applied to a piston or diaphragm and transmitted through hydraulic lines to a dial indicator based on a Bourdon tube or electronic sensor. Electronic digital scales display weight as a number, usually on a liquid crystal display (LCD). They are versatile because they may perform calculations on
W & T Avery - Misplaced Pages Continue
3444-422: The eardrum to the oval window of the cochlea . The lever is a movable bar that pivots on a fulcrum attached to a fixed point. The lever operates by applying forces at different distances from the fulcrum, or a pivot. As the lever rotates around the fulcrum, points further from this pivot move faster than points closer to the pivot. Therefore, a force applied to a point further from the pivot must be less than
3526-400: The 1940s, various electronic devices were being attached to these designs to make readings more accurate. Load cells – transducers that convert force to an electrical signal – have their beginnings as early as the late nineteenth century, but it was not until the late twentieth century that their widespread usage became economically and technologically viable. A mechanical scale or balance
3608-467: The 3rd century BC and were provided, by common belief, by the Greek mathematician Archimedes , who famously stated "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world." Autumn Stanley argues that the digging stick can be considered the first lever, which would position prehistoric women as the inventors of lever technology. A lever is a beam connected to ground by
3690-451: The 3rd class lever. A compound lever comprises several levers acting in series: the resistance from one lever in a system of levers acts as effort for the next, and thus the applied force is transferred from one lever to the next. Examples of compound levers include scales, nail clippers and piano keys. The malleus , incus and stapes are small bones in the middle ear , connected as compound levers, that transfer sound waves from
3772-901: The Atlas Works in West Bromwich, the Mill Lane Works in Birmingham and the Moat Lane Works in Digbeth. In 1891 the business became a limited company with a board of directors and in 1894 the shares were quoted on the London Stock Exchange. In 1895 the company bought the legendary Soho Foundry in Smethwick, a former steam engine factory owned by James Watt & Co. In 1897 the move was complete and
3854-549: The Toledo Scale Company. A programmable scale has a programmable logic controller in it, allowing it to be programmed for various applications such as batching, labeling, filling (with check weight function), truck scales , and more. Another important function is counting, e. g. used to count small parts in larger quantities during the annual stock taking. Counting scales (which can also do just weighing) can range from mg to tonnes. The scales (specifically,
3936-625: The UK by the International Organization of Legal Metrology . An industrial weighing scale is a device that measures the weight or mass of objects in various industries. It can range from small bench scales to large weighbridges, and it can have different features and capacities. Industrial weighing scales are used for quality control, inventory management, and trade purposes. There are many kinds of industrial weighing scales that are used for different purposes and applications. Some of
4018-578: The adjective levis , meaning "light" (as in "not heavy"). The word's primary origin is the Proto-Indo-European stem legwh- , meaning "light", "easy" or "nimble", among other things. The PIE stem also gave rise to the English word "light". The earliest evidence of the lever mechanism dates back to the ancient Near East c. 5000 BC , when it was first used in a simple balance scale . In ancient Egypt c. 4400 BC ,
4100-483: The beam is as close to equilibrium as possible. In precision balances, a more accurate determination of the mass is given by the position of a sliding mass moved along a graduated scale. A decimal balance uses the lever in which the arm for weights is 10 times longer than the arm for weighted objects, so that much lighter weights may be used to weigh heavy object. Similarly a centesimal balance uses arms in ratio 1:100. Unlike spring-based scales, balances are used for
4182-611: The commercial brand of Avery Weigh-Tronix. In September 2007, Illinois Tool Works acquired Avery Berkel from Avery Weigh-Tronix. Illinois Tool Works acquired Avery Weigh-Tronix one year later, but kept the two companies separate. In 2015, the Avery museum, which had existed for almost nine decades, was closed and the collection dispersed. Avery Berkel is a brand and major manufacturer of commercial weighing machines owned by Illinois Tool Works . The Avery Berkel product range includes: The company has made several large acquisition over
SECTION 50
#17327807259634264-412: The common types are: Weighbridges : A large scale that can weigh trucks, lorries, containers, and other heavy-duty vehicles. They are used in industries like manufacturing, shipping, mining, agriculture, etc Container Stacker Scale : A container stacker scale is a specialized weighing system designed for accurately measuring the weight of shipping containers. It is typically integrated into
4346-625: The company was again renamed to be called Avery Weigh-Tronix with Avery Berkel continuing to operate as a brand. The company is based in Smethwick , West Midlands, United Kingdom. The undocumented origin of the company goes back to 1730 when James Ford established the business in Digbeth . On Joseph Balden the then owner's death in 1813 William and Thomas Avery took over his scalemaking business and in 1818 renamed it W & T Avery. The business rapidly expanded and in 1885 they owned three factories:
4428-460: The company was taken over by GEC in 1979. Keith Hodgkinson, managing director at the time, completed the turn-around from mechanical to electronic weighing with a complete overhaul of the product range of retail scales and industrial platform scales. Avery Berkel started in 1993 when the British conglomerate General Electric Company combined their GEC Avery (formerly W & T Avery) business with
4510-429: The contents of the pans as a center-beam balance can. To reduce the need for small graduated reference masses, a sliding weight called a poise can be installed so that it can be positioned along a calibrated scale. A poise adds further intricacies to the calibration procedure, since the exact mass of the poise must be adjusted to the exact lever ratio of the beam. For greater convenience in placing large and awkward loads,
4592-432: The displacement of the spring by any variety of mechanisms to produce an estimate of the gravitational force applied by the object. Rack and pinion mechanisms are often used to convert the linear spring motion to a dial reading. Spring scales have two sources of error that balances do not: the measured mass varies with the strength of the local gravitational force (by as much as 0.5% at different locations on Earth), and
4674-642: The earliest design for such a device dates to 1770 and credits Richard Salter, an early scale-maker. Spring scales came into wide usage in the United Kingdom after 1840 when R. W. Winfield developed the candlestick scale for weighing letters and packages, required after the introduction of the Uniform Penny Post . Postal workers could work more quickly with spring scales than balance scales because they could be read instantaneously and did not have to be carefully balanced with each measurement. By
4756-435: The elasticity of the measurement spring can vary slightly with temperature. With proper manufacturing and setup, however, spring scales can be rated as legal for commerce. To remove the temperature error, a commerce-legal spring scale must either have temperature-compensated springs or be used at a fairly constant temperature. To eliminate the effect of gravity variations, a commerce-legal spring scale must be calibrated where it
4838-400: The equipment used for loading and unloading containers, such as container handlers or stacker cranes. Container stacker scales provide real-time weight measurements, allowing logistics professionals to ensure that each container is loaded within the specified weight limits. Container stacker scales are used in industries like ports, shipping, and logistics Forklift scale : A forklift scale
4920-421: The force located at a point closer in, because power is the product of force and velocity. If a and b are distances from the fulcrum to points A and B and the force F A applied to A is the input and the force F B applied at B is the output, the ratio of the velocities of points A and B is given by a/b , so we have the ratio of the output force to the input force, or mechanical advantage,
5002-400: The forces that are perpendicular to the radial segments PA and PB . The principle of virtual work states that at equilibrium the generalized force is zero, that is F θ = a F A − b F B = 0. {\displaystyle F_{\theta }=aF_{A}-bF_{B}=0.\,\!} Thus, the ratio of the output force F B to
SECTION 60
#17327807259635084-402: The fulcrum and the parallelogram below them. The advantage of the Roberval design is that no matter where equal weights are placed in the pans, the scale will still balance. Further developments have included a "gear balance" in which the parallelogram is replaced by any odd number of interlocking gears greater than one, with alternating gears of the same size and with the central gear fixed to
5166-542: The fulcrum to the input point A and to the output point B , respectively. Now introduce the unit vectors e A and e B from the fulcrum to the point A and B , so r A − r P = a e A , r B − r P = b e B . {\displaystyle \mathbf {r} _{A}-\mathbf {r} _{P}=a\mathbf {e} _{A},\quad \mathbf {r} _{B}-\mathbf {r} _{P}=b\mathbf {e} _{B}.} The velocity of
5248-436: The growth continued with the addition of specialised shops for cast parts, enamel paints and weighbridge assembly and the product range diversified into counting machines, testing machines, automatic packing machines and petrol pumps. During the second world war the company also produced various types of heavy guns. At that time the site underwent severe damage from parachute mines and incendiary bombs, some of many which landed on
5330-426: The input force F A is obtained as M A = F B F A = a b , {\displaystyle MA={\frac {F_{B}}{F_{A}}}={\frac {a}{b}},} which is the mechanical advantage of the lever. This equation shows that if the distance a from the fulcrum to the point A where the input force is applied is greater than the distance b from fulcrum to
5412-812: The item for tampering or returns. In most cases, these types of scales have a sealed calibration so that the reading on the display is correct and cannot be tampered with. In the US, the scales are certified by the National Type Evaluation Program (NTEP), in South Africa by the South African Bureau of Standards , in Australia, they are certified by the National Measurement Institute (NMI) and in
5494-423: The measurement and transmit it to other digital devices. On a digital scale, the force of the weight causes a spring to deform, and the amount of deformation is measured by one or more transducers called strain gauges . A strain gauge is a conductor whose electrical resistance changes when its length changes. Strain gauges have limited capacity and larger digital scales may use a hydraulic transducer called
5576-531: The newly acquired Berkel company. The group continued as a subsidiary of GEC (and later Marconi plc ) until March 2000 when the business was in turn acquired for £102.5 million by the US-American company Weigh-Tronix to form Avery Weigh-Tronix . Avery Berkel continued to operate as a brand of the newly created company with GEC Avery being absorbed by the Avery Berkel brand. Avery Berkel continued as
5658-409: The output force "load" or "resistance". This allows the identification of three classes of levers by the relative locations of the fulcrum, the resistance and the effort: These cases are described by the mnemonic fre 123 where the f fulcrum is between r and e for the 1st class lever, the r resistance is between f and e for the 2nd class lever, and the e effort is between f and r for
5740-399: The output force is applied (point B ), then the lever amplifies the input force. On the other hand, if the distance a from the fulcrum to the input force is less than the distance b from the fulcrum to the output force, then the lever reduces the input force. The use of velocity in the static analysis of a lever is an application of the principle of virtual work . A lever is modeled as
5822-416: The point P that defines the fulcrum be r P , and introduce the lengths a = | r A − r P | , b = | r B − r P | , {\displaystyle a=|\mathbf {r} _{A}-\mathbf {r} _{P}|,\quad b=|\mathbf {r} _{B}-\mathbf {r} _{P}|,} which are the distances from
5904-562: The points A and B are obtained as v A = θ ˙ a e A ⊥ , v B = θ ˙ b e B ⊥ , {\displaystyle \mathbf {v} _{A}={\dot {\theta }}a\mathbf {e} _{A}^{\perp },\quad \mathbf {v} _{B}={\dot {\theta }}b\mathbf {e} _{B}^{\perp },} where e A and e B are unit vectors perpendicular to e A and e B , respectively. The angle θ
5986-493: The precision measurement of mass as their accuracy is not affected by variations in the local gravitational field. (On Earth, for example, these can amount to ±0.5% between locations. ) A change in the strength of the gravitational field caused by moving the balance does not change the measured mass, because the moments of force on either side of the center balanced beam are affected equally. A center beam balance will render an accurate measurement of mass at any location experiencing
6068-508: The reign of Sneferu (c. 2600 BC) excavated, though earlier usage has been proposed. Carved stones bearing marks denoting mass and the Egyptian hieroglyphic symbol for gold have been discovered, which suggests that Egyptian merchants had been using an established system of mass measurement to catalog gold shipments or gold mine yields. Although no actual scales from this era have survived, many sets of weighing stones as well as murals depicting
6150-553: The seal of the U.S. Department of the Treasury and the Federal Trade Commission . Scales are also the symbol for the astrological sign Libra . Scales (specifically, a two-pan, beam balance in a state of equal balance) are the traditional symbol of Pyrrhonism indicating the equal balance of arguments used in inducing epoche . Although records dating to the 1700s refer to spring scales for measuring mass,
6232-431: The spring or set on a pivot and bearing platform. In a spring scale, the spring either stretches (as in a hanging scale in the produce department of a grocery store ) or compresses (as in a simple bathroom scale). By Hooke's law , every spring has a proportionality constant that relates how hard it is pulled to how far it stretches. Weighing scales use a spring with a known spring constant (see Hooke's law ) and measure
6314-415: The steam engine business was gradually converted to pure manufacture of weighing machines. The turn of the century was marked by managing director William Hipkins' determined efforts to broaden the renown of the Avery brand and transform the business into a specialist manufacturer of weighing machines. By 1914 the company occupied an area of 32,000 m² and had some 3000 employees. In the inter-war period,
6396-495: The town of Smethwick. From 1931 to 1973 the company occupied the 18th-century Middlesex Sessions House in Clerkenwell as its headquarters. Changes in weighing machine technology after World War II led to the closure of the foundry, the introduction of load cells and electronic weighing with the simultaneous gradual disappearance of purely mechanical devices. After almost a century of national and international expansion
6478-560: The use of balance scales suggest widespread usage. Examples, dating c. 2400–1800 BC , have also been found in the Indus River valley . Uniform, polished stone cubes discovered in early settlements were probably used as mass-setting stones in balance scales. Although the cubes bear no markings, their masses are multiples of a common denominator. The cubes are made of many different kinds of stones with varying densities. Clearly their mass, not their size or other characteristics,
6560-486: The years that help contribute to its large size. At some point, the company owned Haseley Manor , in Warwickshire. Weighing machine The traditional scale consists of two plates or bowls suspended at equal distances from a fulcrum . One plate holds an object of unknown mass (or weight ), while objects of known mass or weight, called weights , are added to the other plate until mechanical equilibrium
6642-891: Was a factor in sculpting these cubes. In China, the earliest weighing balance excavated was from a tomb of the State of Chu of the Chinese Warring States Period dating back to the 3rd to 4th century BC in Mount Zuojiagong near Changsha , Hunan. The balance was made of wood and used bronze masses. Variations on the balance scale, including devices like the cheap and inaccurate bismar (unequal-armed scales), began to see common usage by c. 400 BC by many small merchants and their customers. A plethora of scale varieties each boasting advantages and improvements over one another appear throughout recorded history, with such great inventors as Leonardo da Vinci lending
6724-400: Was the first mass measuring instrument invented. In its traditional form, it consists of a pivoted horizontal lever with arms of equal length – the beam or tron – and a weighing pan suspended from each arm (hence the plural name " scales " for a weighing instrument). The unknown mass is placed in one pan and standard masses are added to the other pan until
#962037