To correctly answer the question posed in the task, it is necessary to distinguish them from each other.
Body weight is a physical characteristic that does not depend on any factors. It remains constant anywhere in the Universe. Its unit of measurement is kilogram. The physical essence at the conceptual level lies in the body’s ability to quickly change its speed, for example, to slow down to a complete stop.
The weight of a body characterizes the force with which it presses on the surface. Moreover, like any force, it depends on the acceleration given to the body. On our planet it affects all bodies same acceleration(gravitational acceleration; 9.8 m/s 2). Accordingly, on another planet, body weight will change.
Gravity is the force with which the planet attracts a body; it is numerically equal to the weight of the body.
Devices for measuring weight and body weight
The instrument for measuring mass is the well-known scale. The first type of scales were mechanical ones, which are still widely used today. Later they were joined by electronic scales, which have very high measurement accuracy.
In order to measure body weight, you need to use a device called a dynamometer. Its name translates as a force meter, which corresponds to the meaning of the term body weight defined in the previous section. Just like scales, they are mechanical type(lever, spring) and electronic. Weight is measured in Newtons.
Instruments for measuring mass are called scales. At each weighing, at least one of four basic operations is performed
1. determination of unknown body weight (“weighing”),
2. measuring a certain amount of mass (“weighing”),
3. determination of the class to which the body to be weighed belongs (“tariff”
level weighing" or "sorting"),
4. weighing a continuously flowing material flow.
The measurement of mass is based on the use of the law of universal gravitation, according to which the Earth's gravitational field attracts mass with a force proportional to that mass. The force of attraction is compared with a known force created in various ways:
1) a load of known mass is used for balancing;
2) a balancing force occurs when the elastic element is deformed;
3) the balancing force is created by a pneumatic device;
4) a balancing force is created hydraulic device;
5) the balancing force is created electrodynamically using a solenoid winding located in a constant magnetic field;
6) a balancing force is created when a body is immersed in a liquid.
The first method is classic. The measure in the second method is the amount of deformation; in the third - air pressure; in the fourth - fluid pressure; in the fifth - the current flowing through the winding; in the sixth - immersion depth and lifting force.
Classification of scales
1. Mechanical.
2. Electromechanical.
3. Optomechanical.
4. Radioisotope.
Lever trade scales
Commercial mechanical scales RN-3TS13UM
Mechanical scales are based on the principle of comparing masses using levers, springs, pistons and scales.
In electromechanical scales, the force developed by the mass being weighed is measured through the deformation of the elastic element using strain gauge, inductive, capacitive and vibration-frequency transducers.
Modern stage development of laboratory balances, characterized by relatively low speed and significant susceptibility to external influences, is characterized by the increasing use in them to create a balancing force (torque) of electric power exciters with electronic system automatic control (AVR), which ensures the return of the measuring part of the scale to its original equilibrium position. SAR electronic lab. scales (Fig. 4) includes a sensor, for example, in the form of a differential transformer; its core is fixed to the measuring part and moves in a coil mounted on the base of the scale with two windings, the output voltage of which is supplied to the electronic unit. Sensors are also used in the form of an electro-optical device with a mirror on the measuring part that directs a beam of light to a differential photocell connected to the electronic unit. When the measuring part of the scale deviates from the initial equilibrium position, the relative position of the sensor elements changes, and a signal containing information about the direction and magnitude of the deviation appears at the output of the electronic unit. This signal is amplified and converted by the electronic unit into current, which is supplied to a power exciter coil mounted on the base of the scale and interacts with a permanent magnet on its measuring part. The latter, thanks to the counteracting force that arises, returns to its original position. The current in the exciter coil is measured with a digital microammeter calibrated in mass units. In electronic scales with an upper position of the load-receiving cup, a similar automatic balancing scheme is used, but the permanent magnet of the force exciter is mounted on a rod carrying the cup (electronic-lever-less scales) or is connected to this rod with a lever (electronic-lever scales).
Schematic diagram electronic lab. scales: 1 - sensor; 2-core; 3, 5-correspondences of the sensor coil and the exciter; 4-power exciter; 6-permanent magnet; 7-rod; 8-weight-receiving cup; 9-electronic unit; 10-power supply; 11-digit readout device.
Vibration frequency (string). Its action is based on changing the frequency of a tense metal string installed on an elastic element, depending on the magnitude of the force applied to it. The influence of external factors (humidity, temperature, atmospheric pressure, vibration), as well as the complexity of manufacturing, have led to the fact that this type of sensor has not found wide application.
Vibration-frequency sensor of electronic scales from TVES. An elastic element 2 is attached to the base 1, in the hole of which there is a string 3, made integral with it. On both sides of the string there are coils of an electromagnet 4 and an inductive-type displacement transducer 5. A rigid plate 6 with supports 7 is attached to the upper surface of the elastic element, on which the base of the load-receiving platform is placed. To limit the deformation of the elastic element there is a safety rod 8.
Electronic table scales.
weighing range - 0.04–15 kg;
resolution - 2/5 g;
sampling of tare weight - 2 kg;
average service life - 8 years;
accuracy class according to GOST R 53228 - III average;
AC power parameters - 187–242 / 49 - 51 V/Hz;
power consumption - 9 W;
overall dimensions - 295×315×90 mm;
weight - 3.36 kg;
overall dimensions (with packaging) - 405×340×110 mm;
weight (with packaging) - 4.11 kg.
Recently, electromechanical scales with a quartz piezoelectric element have become widely used. This piezoelectric element is a thin (no more than 200 microns) plane-parallel quartz plate rectangular shape with electrodes located in the center on both sides of the plate. The sensor has two piezoelectric elements glued to elastic elements, which implement a differential loading scheme for the transducers. The force of gravity of the load causes compression of one elastic element and stretching of the other.
Scales from the Mera company with an external display device PVm-3/6-T, PVm-3/15-T, PVm-3/32-T. Three ranges: (1.5; 3; 6), (3; 6; 15), (3; 6; 32) kg.
The principle of operation of the scales is based on the transformation of the deformation of the elastic element of the load cell, which occurs under the influence of gravity of the load, into an electrical signal whose amplitude (strain gauge sensor) or frequency (strain quartz sensor) varies in proportion to the mass of the load.
Thus, in terms of the method of installation on a deformable body, transducers of this type are similar to strain gauges. For this reason, they are called strain gauge quartz transducers. In the body of each piezoelectric element, self-oscillations are excited at a natural frequency, which depends on mechanical stress, arising in the piezoelectric element under the influence of load. The output signal of the converter, like that of a vibration frequency sensor, is a frequency in the range of 5...7 kHz. However, strain gauge quartz converters have a linear static characteristic and this is their advantage. Sensitive elements are isolated from environment, which reduces the error due to fluctuations in ambient air humidity. In addition, using a separate temperature-sensitive quartz resonator, a correction is made for changes in temperature in the active zone of the sensor.
Radioisotope weight converters are based on measuring the intensity of ionizing radiation passed through the mass being measured. For an absorption type converter, the radiation intensity decreases with increasing material thickness, and for a scattered radiation converter, the intensity of the perceived
scattered radiation increases with increasing material thickness. The distinguishing features of radioisotope scales are low measured forces, versatility and insensitivity to high temperatures, while electromechanical scales with strain gauge transducers are low cost and high measurement accuracy.
Weighing and weighing devices
According to their intended purpose, weighing and weight-dosing devices are divided into the following six groups:
1) discrete scales;
2) continuous scales;
3) discrete action dispensers;
4) continuous dispensers;
5) standard scales, weights, mobile weighing equipment;
6) devices for special measurements.
To the first group include laboratory scales various types, representing a separate group of weights with special conditions and weighing methods requiring high precision indications; table scales with the highest weighing limit (LWL) up to 100 kg, platform mobile and mortise scales with LWL up to 15 t; platform scales stationary, automobile, trolley, carriage (including for weighing on the move); scales for the metallurgical industry (these include charge feeding systems for powering blast furnaces, electric railcar scales, coal loading scales for coke batteries, weighing trolleys, scales for liquid metal, scales for blooms, ingots, rolled products, etc.).
Scales of the first group are made with scale-type rocker arms, dial square indicators and digital indicating and printing indicating devices and remote controls. To automate weighing, printing devices are used to automatically record weighing results, sum up the results of several weighings, and devices that provide remote transmission of scale readings.
To the second group include continuous conveyor and belt scales, which continuously record the mass of transported material. Conveyor scales differ from continuous belt scales in that they are made in the form of a separate weighing device installed on a certain section of the conveyor belt. Belt scales are independent short-length belt conveyors equipped with a weighing device.
To the third group include dispensers for total accounting (portion scales) and dispensers for packaging bulk materials, used in technological processes of various sectors of the national economy.
To the fourth group include continuous dispensers used in various technological processes that require a continuous supply of material with a given productivity. In principle, continuous dispensers are designed to regulate the supply of material to the conveyor or to regulate the belt speed.
Fifth group includes metrological scales for verification work, as well as weights and mobile verification equipment.
Sixth group includes various weighing devices that are used to determine not mass, but other parameters (for example, calculating equilibrium parts or products, determining the torque of engines, the percentage of starch in potatoes, etc.).
Control is carried out according to three conditions: the norm, less than the norm and more than the norm. The measure is the current in the electromagnet coil. The discriminator is a weighing system with a table 3 and an electromagnetic device 1, an inductive displacement transducer 2 with an output amplifier and a relay device 7. With a normal mass of control objects, the system is in an equilibrium state, and the objects are moved by a conveyor 6 to the place of their collection. If the mass of the object deviates from the norm, then the table 3, as well as the core of the inductive converter, shifts. This causes a change in the current in the inductor circuit and the voltage across the resistor R. The relay discriminator turns on actuator 4, throwing an object from the conveyor belt. The relay device can be three-position with a switch contact, which allows you to throw objects to the right or left relative to the conveyor belt, depending on whether the mass of the rejected object is less or more than the norm. This example clearly shows that the result of control is not numerical value controlled quantity, and the event is whether the object is suitable or not, i.e. whether the controlled quantity is within the specified limits or not.
Weights GOST OIML R 111-1-2009 – interstate standard.
1. Standard weights. To reproduce and store a unit of mass
2. General purpose weights. SI masses in the spheres of action of MMC and N.
3. Calibration weights. For adjusting scales.
4. Special weights. For individual needs of the customer and according to his drawings. For example, specially shaped, carat, Newtonian weights, with a radial cut, hooks, built into weighing systems, for example, for adjusting dispensers.
Standard weight E 500 kg F2(+) TsR-S (collapsible or composite)
Accuracy class F2, permissible error 0...8000 mg
Home / Classification of weights / Accuracy classes
Classification of weights by categories and accuracy classes.
In accordance with GOST OIML R 111-1-2009, weights are divided into 9 accuracy classes, differing mainly in the accuracy of mass reproduction.
Table of classification of weights by accuracy classes. Limits of permissible error ± δm. Accuracy in mg.
| Nominal mass of weights | Kettlebell class | ||||||||
| E1 | E2 | F1 | F2 | M1 | M1-2 | M2 | M2-3 | M3 | |
| 5000 kg | |||||||||
| 2000 kg | |||||||||
| 1000 kg | |||||||||
| 500 kg | |||||||||
| 200 kg | |||||||||
| 100 kg | |||||||||
| 50 kg | |||||||||
| 20 kg | |||||||||
| 10 kg | 5,0 | ||||||||
| 5 kg | 2,5 | 8,0 | |||||||
| 2 kg | 1,0 | 3,0 | |||||||
| 1 kg | 0,5 | 1,6 | 5,0 | ||||||
| 500 g | 0,25 | 0,8 | 2,5 | 8,0 | |||||
| 200 g | 0,10 | 0,3 | 1,0 | 3,0 | |||||
| 100 g | 0,05 | 0,16 | 0,5 | 1,6 | 5,0 | ||||
| 50 g | 0,03 | 0,10 | 0,3 | 1,0 | 3,0 | ||||
| 20 g | 0,025 | 0,08 | 0,25 | 0,8 | 2,5 | 8,0 | |||
| 10 g | 0,020 | 0,06 | 0,20 | 0,6 | 2,0 | 6,0 | |||
| 5 g | 0,016 | 0,05 | 0,16 | 0,5 | 1,6 | 5,0 | |||
| 2 g | 0,012 | 0,04 | 0,12 | 0,4 | 1,2 | 4,0 | |||
| 1 g | 0,010 | 0,03 | 0,10 | 0,3 | 1,0 | 3,0 | |||
| 500 mg | 0,008 | 0,025 | 0,08 | 0,25 | 0,8 | 2,5 | |||
| 200 mg | 0,006 | 0,020 | 0,06 | 0,20 | 0,6 | 2,0 | |||
| 100 mg | 0,005 | 0,016 | 0,05 | 0,16 | 0,5 | 1,6 | |||
| 50 mg | 0,004 | 0,012 | 0,04 | 0,12 | 0,4 | ||||
| 20 mg | 0,003 | 0,010 | 0,03 | 0,10 | 0,3 | ||||
| 10 mg | 0,003 | 0,008 | 0,025 | 0,08 | 0,25 | ||||
| 5 mg | 0,003 | 0,006 | 0,020 | 0,06 | 0,20 | ||||
| 2 mg | 0,003 | 0,006 | 0,020 | 0,06 | 0,20 | ||||
| 1 mg | 0,003 | 0,006 | 0,020 | 0,06 | 0,20 |
Mass ratings of weights indicate the highest and lowest rated weights allowed in any class, as well as the limits of permissible error that should not apply to higher and lower values. For example, the minimum nominal mass value for a class M2 weight is 100 mg, while the maximum value is 5000 kg. A weight with a nominal mass of 50 mg will not be accepted as a Class M2 weight under this standard, but instead must meet the error limits and other requirements for Class M1 (e.g., shape and markings) for that accuracy class of weights. Otherwise, the weight is not considered to comply with this standard.
"Electrical Appliances" - Lamp sockets, etc. Mixer. Thermal. Electrical engineering. Goals and objectives. Circuit breakers. Household electrical appliances. Educational topic: Household electrical appliances. Alternating current. Direct current. Electrical installation devices. Wiring. Types of electrical wiring. Appliances. The list of electrical appliances is very long.
“Weight and mass” - Progress of the experiment. WEIGHT and WEIGHTLESSNESS. Scientific data and observations. Project overview. You can get closer to weightlessness if you move at a certain speed along a convex trajectory. Who and when first began to study the fall of bodies in the air? The book “Unsolved Mysteries of Humanity” published by Reader's Digest.
“Weight of the backpack” - Recommendations for students: Weigh the backpacks without school supplies from the students in our class. Perform exercises to strengthen the muscles of the torso. Subject of research: schoolchildren’s posture. Project - research. I will maintain my health, I will help myself. Our backpacks. Research results: “What’s in our backpacks?”
“Magnifying devices” - Lenses. A hand-held magnifying glass provides magnification from 2 to 20 times. The product will indicate the magnification that the microscope is currently providing. Tripod. Historical reference. Biology is the science of life, living organisms living on earth. Tube. Biology is the science of life. Laboratory work No. 1. 4. Place the finished preparation on the stage opposite the hole in it.
“Weight and air pressure” - What is the atmosphere? How can you weigh gas? What causes atmospheric pressure? Does the atmosphere have weight? Measuring atmospheric pressure. Let's answer the questions: Can the atmosphere “pressure”? What causes gas pressure? Why does water rise after the piston? What is the name of the device for measuring atmospheric pressure?
"Measuring instruments" - The thermometer is glass tube, sealed on both sides. Pressure gauge. Dynamometer. Medical dynamometer. To measure means to compare one quantity with another. Each device has a scale (division). Aneroid barometer. Barometer. Thermometer. Devices make human life a lot easier. Strength meter. Types of dynamometers.
Scales (device) Scales, a device for determining the mass of bodies by the force of gravity acting on them. V. is sometimes also called instruments for measuring other physical quantities that are converted for this purpose into force or moment of force. Such devices include, for example, current scales And Pendant scales. The sequence of actions when determining the mass of bodies in the east is discussed in Art. Weighing.
V. is one of the oldest devices. They arose and improved with the development of trade, production and science. The simplest V. in the form of an equal-arm rocker with suspended cups ( rice. 1) were widely used in barter trade in Ancient Babylon (2.5 thousand years BC) and Egypt (2 thousand years BC). Somewhat later, unequal-shoulder V. with a movable weight appeared (see. Steelyard). Already in the 4th century. BC e. Aristotle gave a theory of such V. (rule moments of force). In the 12th century The Arab scientist al-Khazini described cups with cups whose error did not exceed 0.1%. They were used to determine the density of various substances, which made it possible to recognize alloys, identify counterfeit coins, and distinguish gems from fake ones, etc. In 1586 Galileo To determine the density of bodies, he designed special hydrostatic V. General theory V. was developed by L. Euler (1747).
The development of industry and transport led to the creation of vehicles designed for heavy loads. At the beginning of the 19th century. decimal Vs were created. ( rice. 2) (with a weight-to-load ratio of 1:10 - Quintenz, 1818) and hundredth V. (V. Fairbanks, 1831). At the end of the 19th - beginning of the 20th centuries. With the development of continuous production, weighing machines appeared for continuous weighing (conveyor, dosing, etc.). In various branches of agriculture, industry, and transport, weighers of a wide variety of designs began to be used for weighing specific types of products (in agriculture, for example, grains, root vegetables, eggs, etc.; in transport - cars, railways. carriages, airplanes; in industry - from the smallest details and assemblies in precision instrument making to multi-ton ingots in metallurgy). For scientific research, designs of precision tests were developed - analytical, microanalytical, assay, etc.
Depending on their purpose, weights are divided into standard (for calibrating weights), laboratory (including analytical) and general purpose, used in various fields of science, technology and the national economy.
According to the principle of operation, voltages are divided into lever, spring, electric strain gauge, hydrostatic, and hydraulic.
Lever valves are the most common; their action is based on the law of equilibrium. lever The fulcrum of the lever (“rocker arms” V.) can be in the middle (equal-arm V.) or be shifted relative to the middle (unequal-arm and single-arm V.). Many lever machines (for example, commercial, automobile, portion, etc.) are a combination of levers of the 1st and 2nd types. The supports for the levers are usually prisms and cushions made of special steel or hard stone (agate, corundum). On equal-arm lever weights, the body being weighed is balanced by weights, and some excess (usually 0.05 – 0.1%) of the weight of the weights over the weight of the body (or vice versa) is compensated by the moment created by the rocker arm (with an arrow) due to the displacement of its center of gravity relative to the original position ( rice. 3). The load compensated by the displacement of the center of gravity of the rocker arm is measured using a reading scale. The value of division s of the lever V. scale is determined by the formula
s = k(P o c / lg),
where P 0
‒ the weight of the rocker arm with the arrow, c ‒ the distance between the center of gravity of the rocker arm and the axis of its rotation, l ‒ the length of the rocker arm, g ‒ acceleration
free fall, k is a coefficient that depends only on the resolution of the reading device. The division value, and, consequently, the sensitivity of the V., can be changed within certain limits (usually by moving a special weight that changes the distance c).
In a number of lever laboratory V., part of the measured load is compensated by the force of electromagnetic interaction - retraction of the iron core connected to the rocker arm into a stationary solenoid. The current strength in the solenoid is adjustable electronic device, leading V. to equilibrium. By measuring the current strength, they determine the load V proportional to it. V. of this type are brought to the equilibrium position automatically, so they are usually used for measuring changing masses (for example, when studying oxidation processes, condensation, etc.), when it is inconvenient or impossible to use conventional V. The center of gravity of the rocker arm is combined in these V. with the axis of rotation.
In laboratory practice, weights (especially analytical ones) with built-in weights for part of the load or for the full load are increasingly being used ( rice. 4). The principle of operation of such V. was proposed by D.I. Mendeleev. Specially shaped weights are suspended from the shoulder on which the load cup is located (single-arm weights), or (less commonly) from the opposite shoulder. In single-arm V. ( rice. 5) the error due to the unequal arms of the rocker is completely eliminated.
Modern laboratory scales (analytical, etc.) are equipped with a number of devices to increase the accuracy and speed of weighing: vibration dampers of cups (air or magnetic), doors, when opened, there is almost no air flow, heat shields, mechanisms for applying and removing built-in weights, automatically operating mechanisms for selecting built-in weights when balancing B. Projection scales are increasingly being used, making it possible to expand the range of measurements on the reference scale at small angles of deflection of the rocker arm. All this allows you to significantly increase the performance of V.
In high-speed technical quadrant V. ( rice. 6) the measurement limit on the rocker arm deflection scale is 50 – 100% of the maximum load V., usually lying in the range of 20 g – 10 kg. This is achieved by a special design of a heavy rocker arm (quadrant), the center of gravity of which is located significantly below the axis of rotation.
Most types of metrological, standard, analytical, technical, and trade ( rice. 7), medical, carriage, automobile V., as well as automatic and portioned V.
The action of spring and electric strain gauges is based on Hooke’s law (see. Hooke's law).
The sensitive element in spring voltages is a spiral flat or cylindrical spring, which is deformed under the influence of body weight. V.'s readings are measured on a scale along which a pointer connected to a spring moves. It is assumed that after removing the load, the pointer returns to the zero position, that is, no residual deformation occurs in the spring under the influence of the load.
With the help of spring V., they measure not mass, but weight. However, in most cases, the spring scale is graduated in units of mass. Due to the dependence of the acceleration of free fall on geographical latitude and altitude above sea level, the readings of spring V. depend on their location. In addition, the elastic properties of the spring depend on temperature and change over time; all this reduces the accuracy of spring V.
In torsional (torsional) batteries, the sensitive element is an elastic thread or spiral springs ( rice. 8). The load is determined by the angle of twist of the spring thread, which is proportional to the torsional moment created by the load.
The action of electrical strain gauges is based on converting the deformation of elastic elements (columns, plates, rings) that perceive the force of a load into a change in electrical resistance. The transducers are highly sensitive wire strain gauges, glued to elastic elements. As a rule, electric strain gauges (carriage, automobile, crane, etc.) are used for weighing large masses.
Hydrostatic tests are used mainly to determine density solids and liquids. Their action is based on Archimedes' law (see. Hydrostatic weighing).
Hydraulic V. are similar in design hydraulic press.
The readings are taken using a pressure gauge calibrated in mass units.
All types of V. are characterized by: 1) ultimate load - the greatest static load that V. can withstand without violating their metrological characteristics; 2) division value - the mass corresponding to a change in the reading by one scale division; 3) the limit of permissible weighing error - the largest permissible difference between the result of one weighing and the actual mass of the body being weighed;
4) permissible variation of readings - the largest permissible difference in V.’s readings when repeatedly weighing the same body.
Weighing errors on some types of V. at maximum load.
Weighing error at maximum load
Metrological..........
Exemplary 1st and 2nd categories
Exemplary 3rd category and
technical 1st class............
Analytical, semi-microanalytical, microanalytical, assay
Medical........................
Household...................
Automotive........................
Carriage................
Torsional...............
1 kg
20 kg ‒ 1 kg
200 g - 2 g
20 kg ‒ 1 kg
200 g ‒2 g
200 g
100 g
20 g
2 g
1 g
150 kg
20 kg
30 kg ‒ 2 kg
50 t ‒ 10 t
150 t ‒ 50 t
1000 mg ‒ 20 mg
5 mg ‒ 0.5 mg
0.005 mg*
20 mg ‒ 0.5 mg*
1.0 mg ‒ 0.01 mg*
100 mg ‒ 20 mg
10 mg - 0.4 mg
1.0 mg ‒ 0.1 mg*
1.0 mg ‒ 0.1 mg*
0.1 mg ‒ 0.01 mg*
0.02 mg ‒ 0.004 mg*
0.01 mg ‒ 0.004 mg*
50 g
10 g
60 g ‒5 g
50 kg ‒ 10 kg
150 kg ‒ 50 kg
1.0 mg - 0.05 mg
0.01 mg - 0.001 mg
* Using precision weighing methods.
Lit.: Rudo N.M., Libra. Theory, structure, adjustment and verification, M. - L., 1957; Malikov L. M., Smirnova N. A., Analytical electric scales, in the book: Encyclopedia of Control and Automation Measurements, v. 1, M. - L., 1962: Orlov S.P., Avdeev B.A., Weighing equipment of enterprises, M., 1962; Karpin E. B., Calculation and design of weighing mechanisms and dispensers, M., 1963; Gauzner S.I., Mikhailovsky S.S., Orlov V.V., Recording devices in automatic weighing processes, M., 1966.
N. A. Smirnova.
Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what “Scales (device)” is in other dictionaries:
Scales - get a worker at the Academician - SCALES, a device for determining the weight of bodies. In a broader sense, some instruments measure forces of origin other than gravity. 1. Scales for accurate weighing. Currently, the system proposed by... is mainly used. Great Medical Encyclopedia
Ov; pl. 1. Device for determining weight and mass. Laboratory c. Pharmacy v. Electronic v. V. Themis (book; about justice). 2. [with a capital letter] One of the twelve constellations of the Zodiac. 3. About a person born at the end of September October, when... encyclopedic Dictionary
A device for determining the mass of bodies by the force of gravity acting on them. V. sometimes called also instruments for measuring other physics. quantities converted for this purpose into force or moment of force. Such devices include, for example, current balances and torsion... ... Physical encyclopedia Big Polytechnic Encyclopedia
The simplest device for determining mass and weight is a lever scale, known from about the fifth millennium BC. They are a beam that has a support in its middle part. There are cups at each end of the beam. The measurement object is placed on one of them, and weights are placed on the other standard sizes until the system is brought into equilibrium. In 1849, the Frenchman Joseph Beranger patented an improved scale of this type. They had a system of levers under the cups. This type of device has been very popular for many years in trades and kitchens.
A variant of lever scales is the steelyard, known since antiquity. In this case, the suspension point is not in the middle of the beam; the standard load has a constant value. Equilibrium is established by changing the position of the suspension point, and the beam is pre-graduated (according to the lever rule).
Robert Hooke, an English physicist, established in 1676 that the deformation of a spring or elastic material is proportional to the magnitude of the applied force. This law allowed him to create spring scales. Such scales measure force, so they will show different numerical results on Earth and on the Moon.
Currently used to measure mass and weight various methods based on receiving an electrical signal. In the case of measuring very large masses, for example a heavy vehicle, pneumatic and hydraulic systems are used
Instruments for measuring time
The first time meter in history was the Sun, the second was the flow of water (or sand), the third was the uniform combustion of special fuel. Having originated in ancient times, solar, water and fire clocks have survived to our time. The tasks that watch creators faced in ancient times were very different from modern ones. Time meters were not required to be particularly accurate, but they had to divide the days and nights into the same number of hours of varying lengths depending on the time of year. And since almost all instruments for measuring time were based on fairly uniform phenomena, the ancient “watchmakers” had to resort to various tricks to do this.
Sundial.
The oldest sundial was found in Egypt. Interestingly, early Egyptian sundials used the shadow not of a pillar or rod, but of the edge of a wide plate. In this case, only the height of the Sun was measured, and its movement along the horizon was not taken into account.
With the development of astronomy, the complex movement of the Sun was understood: daily along with the sky around the axis of the world and annual along the zodiac. It became clear that the shadow would show the same periods of time, regardless of the height of the Sun, if the rod was directed parallel to the axis of the world. But in Egypt, Mesopotamia, Greece and Rome, day and night, the beginning and end of which marked the sunrise and sunset, were divided, regardless of their length, into 12 hours, or, more roughly, according to the time of changing of the guards, into 4 “guards” of 3 hours each. Therefore, it was necessary to mark on the scales unequal hours tied to certain parts of the year. For large sundial, which were installed in cities, vertical gnomon-obelisks were more convenient. The end of such an obelisk described symmetrical curved lines on the horizontal platform of the foot, depending on the time of year. A number of these lines were applied to the base, and other lines corresponding to the clock were drawn across. Thus, a person looking at the shadow could recognize both the hour and approximately the month of the year. But the flat scale took up a lot of space and could not accommodate the shadow that the gnomon casts when the Sun is low. Therefore, in watches of more modest sizes, the scales were located on concave surfaces. Roman architect of the 1st century. BC. Vitruvius in his book “On Architecture” lists more than 30 types of water and sundials and reports some of the names of their creators: Eudoxus of Cyidae, Aristarchus of Samos and Apollonius of Pergamon. Based on the architect’s descriptions, it is difficult to get an idea of the design of this or that clock, but many of the remains of ancient time meters found by archaeologists were identified with them.
Sundials have a big drawback - the inability to show time at night and even during the day in cloudy weather, but they have an important advantage compared to other clocks - a direct connection with the luminary that determines the time of day. That's why they didn't lose practical significance even in an era of widespread availability of precision mechanical watches that require inspection. The stationary medieval sundials of the countries of Islam and Europe differed little from the ancient ones. True, during the Renaissance, when learning began to be valued, complex combinations of scales and gnomons came into fashion, serving for decoration. For example, at the beginning of the 16th century. A time meter was installed in Oxford University Park, which could serve as a visual aid for constructing various sundials. Since the 14th century, when mechanical tower clocks began to spread, Europe gradually abandoned the division of day and night into equal periods of time. This simplified the sundial scales, and they were often used to decorate the facades of buildings. So that wall clocks could show morning and evening time in the summer, they were sometimes made double with dials on the sides of a prism protruding from the wall. In Moscow, a vertical sundial can be seen on the wall of the Russian humanitarian university on Nikolskaya Street, and in the park of the Kolomenskoye Museum there is a horizontal sundial, unfortunately, without a dial and a gnomon.
The most grandiose sundial was built in 1734 in the city of Jaipur by the maharaja (ruler of the region) and astronomer Sawai-Jai Singh (1686-1743). Their gnomon was a triangular stone wall with a vertical leg height of 27 m and a hypotenuse length of 45 m. The scales were located on wide arcs along which the shadow of the gnomon moved at a speed of 4 m per hour. However, the Sun in the sky does not look like a point, but a circle with an angular diameter of about half a degree, so due to the large distance between the gnomon and the scale, the edge of the shadow was unclear.
Portable sundials were very diverse. IN early middle ages Mostly high-altitude ones were used, which did not require orientation to the cardinal points. In India, watches in the form of a faceted staff were common. On the edges of the staff, hour divisions were applied, corresponding to two months of the year, equidistant from the solstice. The gnomon was a needle, which was inserted into holes made above the divisions. To measure time, the staff was suspended vertically on a cord and turned with a needle towards the Sun, then the shadow of the needle showed the height of the luminary.
In Europe, similar watches were designed in the form of small cylinders, with a number of vertical scales. The gnomon was a flag mounted on a rotating pommel. It was installed above the desired hour line and the clock was rotated so that its shadow was vertical. Naturally, the scales of such watches were “tied” to a certain latitude of the area. In the 16th century In Germany, universal high-altitude sundials in the form of a “boat” were common. The time in them was marked by a ball placed on the thread of a plumb line, when the instrument was pointed at the Sun so that the shadow of the “bow” exactly covered the “stern”. Adjustment in latitude was made by tilting the “mast” and moving a bar along it, on which the plumb line was attached. The main disadvantage of altitude clocks is the difficulty of determining the time from them closer to noon, when the Sun changes altitude extremely slowly. In this sense, a clock with a gnomon is much more convenient, but it must be set according to the cardinal points. True, when they are supposed to be used for a long time in one place, you can find time to determine the direction of the meridian.
Later, portable sundials began to be equipped with a compass, which made it possible to quickly set them in the desired position. Such watches were used until the middle of the 19th century. to check the mechanical ones, although they showed true solar time. The greatest lag of the true Sun from the average during the year is 14 minutes. 2 seconds, and the greatest advance is 16 minutes. 24 seconds, but since the lengths of neighboring days do not differ much, this did not cause any particular difficulties. For amateurs, a sundial with a noon gun was produced. A magnifying glass was placed over the toy cannon, which was positioned so that at noon the collected Sun rays reached the pilot hole. The gunpowder caught fire, and the cannon fired, naturally, with a blank charge, notifying the house that it was true noon and it was time to check the clock. With the advent of telegraph time signals (in England since 1852, and in Russia since 1863), it became possible to check watches in post offices, and with the advent of radio and telephone “talking clocks”, the era of sundials ended.
Water clock.
The religion of ancient Egypt required the performance of night rituals with precise adherence to the time of their performance. Time at night was determined by the stars, but water clocks were also used for this. The oldest known Egyptian water clock dates back to the era of Pharaoh Amenhotep III (1415-1380 BC). They were made in the form of a vessel with expanding walls and a small hole from which water gradually flowed out. The time could be judged by its level. To measure watches of different lengths, several scales were applied to the inner walls of the vessel, usually in the form of a series of dots. The Egyptians of that era divided night and day into 12 hours, and for each month they used a separate scale, near which its name was placed. There were 12 scales, although six would have been enough, since the lengths of days located at the same distance from the solstices are almost the same. There is also another type of clock in which the measuring cup was not emptied, but filled. In this case, water came into it from a vessel placed above in the form of a baboon (this is how the Egyptians depicted the god of wisdom Thoth). The conical shape of the watch bowl with flowing water contributed to a uniform change in the level: when it decreases, the water pressure drops and it flows out more slowly, but this is compensated by a decrease in its surface area. It is difficult to say whether this shape was chosen to achieve uniform “running” of the watch. Perhaps the vessel was made in such a way that it would be easier to examine the scales drawn on its inner walls.
The measurement of equal hours (in Greece they were called equinoxes) was required not only by astronomers; they determined the length of speeches in court. This was necessary so that those speaking for the prosecution and defense were on equal terms. In the surviving speeches of Greek orators, for example, Demosthenes, there are requests to “stop the water,” apparently addressed to the servant of the court. The clock was stopped while the text of the law was read or a witness was interviewed. Such a clock was called a “clepsydra” (Greek for “stealing water”). It was a vessel with holes in the handle and bottom into which a certain amount of water was poured. To “stop the water,” they apparently plugged the hole in the handle. Small water clocks were also used in medicine to measure pulse. Problems of measuring time contributed to the development of technical thought.
A description of a water alarm clock has been preserved, the invention of which is attributed to the philosopher Plato (427-347 BC). "Plato's Alarm Clock" consisted of three vessels. From the upper one (clepsydra) water flowed into the middle one, which contained a bypass siphon. The receiving tube of the siphon ended near the bottom, and the drain tube entered the third empty closed vessel. This in turn was connected by an air tube to the flute. The alarm clock worked like this: when the water in the middle vessel covered the siphon, it turned on. The water quickly poured into the closed vessel, displaced the air from it, and the flute began to sound. To regulate the time the signal turned on, the middle vessel should be partially filled with water before starting the clock.
The more water was pre-filled into it, the earlier the alarm went off.
The era of pneumatic, hydraulic and mechanical devices began with the works of Ctesibius (Alexandria, II-I centuries BC). In addition to various automatic devices that served mainly to demonstrate “technical miracles,” he developed a water clock that automatically adjusted to changes in the length of night and day periods of time. Ctesibius's clock had a dial in the form of a small column. Near her were two figurines of cupids. One of them cried continuously; his “tears” flowed into a tall vessel with a float. The figurine of the second cupid was moved using a float along the column and served as a time indicator. When at the end of the day the water raised the indicator to the highest point, the siphon was triggered, the float was lowered to its original position, and a new daily cycle of operation of the device began. Since the length of the day is constant, the clock did not need to be adjusted to suit the different seasons. The hours were indicated by transverse lines marked on the column. For summer time, the distances between them in the lower part of the column were large, and in the upper part small, depicting short night hours, and in winter, vice versa. At the end of each day, the water flowing from the siphon fell on the water wheel, which, through gears, slightly turned the column, bringing a new part of the dial to the pointer.
Information has been preserved about the watch that Caliph Harun al Rashid gave to Charlemagne in 807. Egingard, the king’s historiographer, reported about them: “A special water mechanism indicated the clock, which was indicated by the striking of a certain number of balls falling into a copper basin. At noon, 12 knights rode out from as many doors that closed behind them.”
The Arab scientist Ridwan created in the 12th century. clock for the great mosque in Damascus and left a description of it. The clock was made in the form of an arch with 12 windows indicating the time. The windows were covered with colored glass and illuminated at night. The figure of a falcon moved along them, which, when it reached the window, dropped balls into the pool, the number of which corresponded to the hour that had come. The mechanisms connecting the clock float to the indicators consisted of cords, levers and blocks.
In China, water clocks appeared in ancient times. In the book "Zhouli", which describes the history of the Zhou dynasty (1027-247 BC), there is a mention of a special servant who "looked after the water clock." Nothing is known about the structure of these ancient clocks, but, given the traditional nature of Chinese culture, it can be assumed that they differed little from the medieval ones. A book by an 11th century scientist is devoted to a description of the design of a water clock. Liu Zaya. The most interesting design described there is a water clock with a surge tank. The clock is arranged in the form of a kind of ladder, on which there are three tanks. The vessels are connected by tubes through which water flows sequentially from one to another. The upper tank supplies the rest with water, the lower one has a float and a ruler with a time indicator. The most important role is assigned to the third “equalization” vessel. The flow of water is adjusted so that the tank receives a little more water from the top than flows out of it into the bottom (the excess is discharged through a special hole). Thus, the water level in the middle tank does not change, and it enters the lower vessel under constant pressure. In China, the day was divided into 12 double hours “ke”.
A tower astronomical clock, remarkable from a mechanical point of view, was created in 1088 by astronomers Su Song and Han Kunliang. Unlike most water clocks, they did not use changes in the level of flowing water, but its weight. The clock was placed in a three-story tower, designed in the form of a pagoda. On top floor In the building there was an armillary sphere, the circles of which, due to the clock mechanism, maintained parallelism to the celestial equator and the ecliptic. This device anticipated the mechanisms for guiding telescopes. In addition to the sphere, in special room there was a star globe that showed the position of the stars, as well as the Sun and Moon relative to the horizon. The tools were driven by a water wheel. It had 36 buckets and automatic scales. When the weight of water in the bucket reached the desired value, the latch released it and allowed the wheel to rotate 10 degrees.
In Europe, water public clocks were used for a long time along with mechanical tower clocks. So in the 16th century. On the main square of Venice there was a water clock, which every hour reproduced the scene of the worship of the Magi. The Moors appeared and struck a bell to mark the time. Interesting clock from the 17th century. are kept in the museum of the French city of Cluny. In them, the role of a pointer was played by a water fountain, the height of which depended on the elapsed time.
After its appearance in the 17th century. Pendulum clocks in France attempted to use water to keep the pendulum swinging. According to the inventor, a tray with a partition in the middle was installed above the pendulum. Water was supplied to the center of the partition, and when the pendulum swung, it pushed it in the desired direction. The device did not become widespread, but the idea behind it to drive the hands from a pendulum was later implemented in an electric clock.
Hourglass and fire clock
Sand, unlike water, does not freeze, and a clock where the flow of water is replaced by the flow of sand can work in winter. The hourglass with a pointer was built around 1360 by the Chinese mechanic Zhai Siyuan. This clock, known as the “five-wheeled sand clepsydra,” was driven by a “turbine” on which sand fell onto the blades. A system of gear wheels transmitted its rotation to the arrow.
In Western Europe, hourglasses appeared around the 13th century, and their development was associated with the development of glassmaking. Early hours were two separate glass bulbs held together with sealing wax. Specially prepared “sand”, sometimes from crushed marble, was carefully sifted and poured into a vessel. The flow of a dose of sand from the top of the clock to the bottom quite accurately measured a certain period of time. The clock could be adjusted by changing the amount of sand poured into it. After 1750, watches were already made in the form of a single vessel with a narrowing in the middle, but they retained a hole plugged with a stopper. Finally, from 1800, hermetic watches with a sealed hole appeared. In them, the sand was reliably separated from the atmosphere and could not become damp.
Back in the 16th century. Churches generally used frames with four hourglasses set at the quarter, half, three-quarter and hour. Based on their condition, it was possible to easily determine the time within the hour. The device was equipped with a dial with an arrow; when the sand flowed out of the last upper vessel, the attendant turned the frame over and moved the arrow one division.
Hourglasses are not afraid of pitching and therefore, until the beginning of the 19th century. were widely used at sea to time watches. When an hour's portion of sand flowed out, the watchman turned the watch over and struck the bell; This is where the expression “break the bells” comes from. The ship's hourglass was considered an important instrument. When the first explorer of Kamchatka, student of the St. Petersburg Academy of Sciences Stepan Petrovich Krasheninnikov (1711-1755), arrived in Okhotsk, ship construction was underway there. The young scientist turned to Captain-Commander Vitus Bering with a request for help in organizing a service for measuring sea level fluctuations. For this, an observer and an hourglass were needed. Bering appointed a competent soldier to the position of observer, but did not give him a watch. Krasheninnikov got out of the situation by digging a water meter opposite the commandant's office, where, according to naval custom, bells were regularly sounded. The hourglass turned out to be a reliable and convenient device for measuring short periods of time and in terms of “survivability” it was ahead of the sunglass. They were recently used in physiotherapy rooms of clinics to control the time of procedures. But they are being replaced by electronic timers.
The combustion of material is also a fairly uniform process on the basis of which time can be measured. Fire clocks were widely used in China. Obviously, their prototype was, and is now popular in Southeast Asia, smoking sticks - slowly smoldering rods that produce aromatic smoke. The basis of such watches were flammable sticks or cords, which were made from a mixture of wood flour and binders. They were often of considerable length, made in the form of spirals and hung over a flat plate into which the ashes fell. By the number of remaining turns one could judge the elapsed time. There were also “fire alarm clocks”. There, the smoldering element was placed horizontally in a long vase. IN in the right place a thread with weights was thrown through it. The fire, having reached the thread, burned it out, and the weights fell with a ringing sound into the copper saucer placed. In Europe, candles with divisions were in use, playing the role of both night lights and time meters. To use them in alarm mode, a pin with a weight was inserted into the candle at the required level. When the wax around the pin melted, the weight along with it fell with a ringing sound into the cup of the candlestick. Oil lamps with glass vessels equipped with a scale were also used to roughly measure time at night. The time was determined by the oil level, which decreased as it burned out.
