Presentation on the topic "electrical measuring instruments". Presentation on the topic of electrical measuring instruments, the device was prepared by a student. Measuring technology presentation
Description of the presentation by individual slides:
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Analog measuring instruments are devices whose readings are a continuous function of changes in the quantity being measured.
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An analog electrical measuring device is, first of all, an indicating device, i.e., a device that allows readings to be taken. To do this, for all analog electrical measuring instruments, regardless of the purpose and the type of measuring mechanism used in it, any device contains components and elements common to all analog instruments: a reading device, consisting of a scale located on the dial of the device, and a device indicator for creating a counteracting and calming moments support device.
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Measuring circuit Measuring mechanism Reading device The measuring circuit is a converter of the measured quantity x into some intermediate electrical quantity y (current, voltage), functionally related to the measured quantity x, i.e. y=f1(x). The electrical quantity y, which is current or voltage, directly affects the measuring mechanism (the input quantity of the mechanism). The measuring circuit contains resistance, inductance, capacitance and other elements. The measuring mechanism is a converter of the electrical energy supplied to it into the mechanical energy necessary to move its moving part relative to the stationary one, i.e. α = f2(y). The input quantities create mechanical forces acting on the moving part. Typically, in mechanisms, the moving part can only rotate around an axis, therefore the mechanical forces acting on the mechanism create a moment M. This moment is called torque M = Wm / α., where Wm is the energy of the magnetic field Reading device - pointer (arrow), pen , rigidly connected to the moving part of the measuring mechanism and a fixed scale (a paper medium that combines the functions of a scale and a carrier of recorded information). The moving part converts the angular movement of the mechanism into the movement of the pointer, and the value α is measured in scale division units. X Y α
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The common elements of analog electromechanical devices are: a housing (made of metal or plastic), a fixed and moving part (a coil, a ferromagnetic core or an aluminum rotating disk), a counteracting device (spiral or tape spring), a damper (liquid or magnetic induction), a zero position corrector and reading device (scale and pointer).
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Depending on the physical phenomena underlying the creation of torque, or, in other words, on the method of converting electromagnetic energy supplied to the device into mechanical energy of movement of the moving part, electromechanical devices are divided into the following main systems: magnetoelectric, electromagnetic, electrodynamic, ferrodynamic, electrostatic, induction.
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The principle of operation of IMs of various groups of devices is based on the interaction of: magnetoelectric IMs - magnetic fields of a permanent magnet and a current-carrying conductor; electromagnetic - the magnetic field created by a current-carrying conductor and a ferromagnetic core; electrodynamic (and ferrodynamic) - magnetic fields of two systems of conductors with currents; electrostatic - two systems of charged electrodes; induction - an alternating magnetic field of a conductor with current and eddy currents induced by this field in a moving element - as a result, an MVR torque is created.
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Depending on the method of creating a counteracting moment Ma, electromechanical SIs are divided into two groups: - with a mechanical counteracting moment; - with electrical counter-torque (logometers).
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A ratiometer is an electrical measuring device for measuring the ratio of the strengths of two electric currents. The moving part is made in the form of two frames located perpendicularly. When a current flows through the frame of the ratiometer, when interacting with the magnetic field of a permanent magnet of an elliptical shape (the fixed part of the ratiometer), a torque is created that moves the needle of the device. When the currents in both frames are equal, their torques are equal, the arrow of the device takes the zero position. If the currents are different, the moving part of the device moves in such a way that the frame with a large current ends up in a position with a large gap of the permanent magnet (due to its ellipticity). As a result, the torque generated by the frame decreases and becomes equal to the torque of the frame with a lower current. A ratiometer is usually used in instruments for measuring resistance, inductance, capacitance, and temperature. A ratiometer is a device in which there are no spiral springs that create a counteracting moment when the needle is turned, and the readings of which do not depend on the magnitude of the current, but depend on the multiple ratio of the currents in the coils. Logometers of magnetoelectric, electrodynamic, ferrodynamic, electromagnetic systems are common. For example, a logometer is a magnetoelectric megohmmeter, a device for measuring temperature complete with a resistance thermometer, etc.
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Magnetoelectric ammeters and voltmeters are the main measuring instruments in direct current circuits. Devices of the magnetoelectric system are based on the principle of interaction of the coil current (frame with current) and the magnetic field of a permanent magnet. The fixed part consists of a permanent magnet 1, its pole pieces 2 and a fixed core 3. There is a strong magnetic field in the gap between the pole pieces and the core. The moving part of the measuring mechanism consists of a light frame 4, the winding of which is wound onto an aluminum frame, and two semi-axes 5, fixedly connected to the frame frame. The ends of the winding are soldered to two spiral springs 6, through which the measured current is supplied to the frame. An arrow 7 and counterweights 8 are attached to the frame. A frame is installed in the gap between the pole pieces and the core. Its axle shafts are inserted into glass or agate bearings. When current passes through the winding of the frame, the latter tends to turn, but its free rotation is counteracted by spiral springs. And the angle at which the frame nevertheless turns, it turns out, corresponds to a certain current strength that flows through the winding of the frame. In other words, the angle of rotation of the frame (arrow) is proportional to the current strength. Ammeters and voltmeters have basically the same measuring mechanisms. Their difference lies only in the electrical resistance of the frames. An ammeter has a much lower frame resistance than a voltmeter.
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When the direction of the current changes, the direction of the torque (determined by the left-hand rule) changes. When a magnetoelectric system device is connected to an alternating current circuit, the coil is acted upon by mechanical forces that rapidly change in value and direction, the average value of which is zero. As a result, the instrument needle will not deviate from the zero position. Therefore, these instruments cannot be used directly for measurements in alternating current circuits. Calming (damping) of the needle in the devices of the magnetoelectric system occurs due to the fact that when the aluminum frame moves in the magnetic field of the permanent magnet NS, eddy currents are induced in it. As a result of the interaction of these currents with the magnetic field, a moment arises that acts on the frame in the direction opposite to its movement, causing the vibrations of the frame to quickly calm down.
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1) with a moving coil and a fixed magnet; 2) with a moving magnet and a fixed coil. with external magnet with internal magnet symbol 1 – stationary permanent magnet; 2 - magnetic circuit; 3- core; 4 – frame; 5 – spring; 6-arrow
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Advantages: high sensitivity, high accuracy, uniform scale, low intrinsic power consumption, low influence of external magnetic fields due to the strong intrinsic magnetic field. Disadvantages: design complexity, high cost, unsuitable for operation in alternating current circuits, sensitivity to overloads and current changes.
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Application: as DC ammeters and voltmeters with measurement limits from nanoamps to kiloamps and from fractions of millivolts to kilovolts, DC galvanometers, AC galvanometers and oscillographic galvanometers; In combination with various types of AC-DC converters, they are used for measurements in AC circuits.
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Prepare presentations: Magnetoelectric galvanometers Magnetoelectric logometers Magnetoelectric ohmmeters Magnetoelectric ammeters and voltmeters
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Electromagnetic system devices operate on the principle of drawing a metal armature into a coil when an electric current passes through it. The operating principle of electromagnetic system devices is based on the interaction of a magnetic field created by a stationary coil, through the winding of which the measured current flows, with one or more ferromagnetic cores mounted on an axis. Fixed coil 3 is a frame with a wound insulated copper tape. When a measured current flows through the coil, a magnetic field is created in its flat slit. Core 5 with arrow 4 is mounted on axis 1. The magnetic field of the coil magnetizes the core and draws it into the slot, turning the axis with arrow. Spiral spring 2 creates a counteracting moment Mpr 1 – axis 2 – spiral spring 3 – coil 4 – arrow 5 – core 6 – damper
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Advantages: simplicity of design, ability to measure direct and alternating currents, ability to withstand large overloads, low cost. Disadvantages: influence of external magnetic fields on instrument readings, uneven scale (quadratic, i.e. compressed at the beginning and stretched at the end), low sensitivity, low accuracy, high power consumption.
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EM system devices are used mainly as panel ammeters and AC voltmeters of industrial frequency of accuracy class 1.0 and lower classes for measurements in AC circuits, in portable multi-range devices of accuracy class 0.5.
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Optical devices for the eye
The images of the objects in question are imaginary.
Angular magnification– the ratio of the angle of view when observing an object through an optical device to the angle of view when observing with the naked eye (characteristics of the optical device).
Magnifier
A magnifying glass is a converging lens or a system of lenses with a short focal length.
h d 0
The angle of view from which an object is visible to the naked eye.
d0 =25cm – distance of best vision. h – linear size of the object.
The magnifying glass is placed close to the eye, and the object is positioned in its focal plane.
h - the angle at which it is visible through a magnifying glass
F subject.
Fd – focal length of the magnifying glass.
Г 0 - angular magnification of the magnifying glass.
The magnification provided by a magnifying glass is limited by its size.
Magnifying glasses are used by watchmakers, geologists, botanists, and criminologists.
Microscope
A microscope is a combination of two lenses or lens systems.
Lens O1 facing the object is called a lens
(gives a real magnification of the image of the object). Lens O2 – eyepiece.
An object is placed between the focal point of the lens and a point at twice the focal length. The eyepiece is placed so that the image coincides with the focal
Microscope magnification is the ratio of the visual angle φ, at which an object is visible when observed through a microscope, to the visual angle ψ when observed with the naked eye from the distance of best vision
d0 =25cm.
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Microscope Magnification |
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For a magnifying glass. |
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For microscope, |
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h’ – linear size of the image given |
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lens. F2 – focal length of the eyepiece. |
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The linear size of the image in the lens is related to the linear size of the object by the ratio:
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F1 – lens focal length. |
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Optical length of microscope tube |
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(distance between rear lens and |
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front focus of the eyepiece). |
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Microscope magnification: from several |
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tens to 1500. |
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F1 F2 |
The microscope allows you to distinguish small |
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details of an object that, when observed, Uchim.net |
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with the naked eye or with a magnifying glass |
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Kepler tube
In 1613 it was made by Christoph Scheiner according to Kepler's design.
Kepler (1571 – 1630)
A lens is a long-focus lens that gives a truly reduced, inverted image of an object. The image of a distant object is obtained in the focal plane of the lens. The eyepiece is located from this image at its focal length.
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The angular magnification of a telescope is the ratio of the visual angle at which we see the image of an object in the telescope to the visual angle at which we see it
the same object directly.
GT - telescope magnification.
The magnification of the telescope is equal to the focal ratio
lens distance to eyepiece focal length.
GT F 1 F2
The Kepler tube produces an inverted image.
Binoculars
Binoculars are two telescopes connected together to view an object with both eyes.
Prism binoculars.
To reduce the size of the Kepler tubes used in binoculars and reverse the image, rectangular total reflection prisms are used.
Pipe
GalileoGalileo built the first telescope with his own hands in 1609.
Galileo Galilei (1564- 1642)
The rays coming from the object pass through the collecting lens and become converging (they would give an inverted, reduced image). They then fall on a diverging lens and become divergent. They give imaginary, direct, magnified
image of an object.
Using his telescope with 30x magnification, Galileo made a number of astronomical discoveries: He discovered mountains on the Moon, spots on the Sun, discovered the four satellites of Jupiter, the phases of Venus, and established that the Milky Way consists of many stars.
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Measuring instruments Measuring instrument p is a measuring instrument designed to obtain the values of the measured physical quantity in a specified range. A measuring device is often called a measuring instrument for producing a signal of measuring information in a form accessible to direct perception by the operator.
Dynamometer Dynamo meter (from ancient Greek δύναμις - “force” and μέτρεω - “I measure”) is a device for measuring force or moment of force, consists of a force link (elastic element) and a reading device. In the power link, the measured force causes deformation, which is directly or through transmission communicated to the reading device. A dynamometer can measure forces from fractions of newtons (N, fractions of kgf) to 1 Mn (100 tf). According to the principle of operation, dynamometers are distinguished between mechanical (spring or lever), hydraulic and electronic. Sometimes two principles are used in one dynamometer. To measure the compression force of doors and gates and other devices with electric, hydraulic and pneumatic drives, in compliance with the requirements of pan-European technical standards, there is a class of dynamometers under the general name Compression force measuring devices. The most famous representatives of this class of measuring instruments are: BIA Klasse 1, FM100, FM200, FM300 from the German company Drive Test GmbH. In spring dynamometers with a coil spring, when the spring is stretched, two types of deformation occur: bending deformation and deformation
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Barometer In liquid barometers, pressure is measured by the height of a column of liquid (mercury) in a tube sealed at the top, and with the lower end lowered into a vessel with liquid (atmospheric pressure is balanced by the weight of the liquid column). Mercury barometers are the most accurate and are used at weather stations. Mechanical barometers (Aneroid) are usually used in everyday life. There is no liquid in an aneroid (Greek “aneroid” - “waterless”). It shows the atmospheric pressure acting on a corrugated thin-walled metal box in which a vacuum is created. When atmospheric pressure decreases, the box expands slightly, and when atmospheric pressure increases, it contracts and acts on the spring attached to it. In practice, several (up to ten) aneroid boxes are often used, connected in series, and there is a lever transmission system that turns a pointer moving on a dial scale graduated from a mercury barometer.
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Ammeter The most common ammeters are those in which the moving part of the device with the pointer rotates through an angle proportional to the magnitude of the current being measured. Ammeters are magnetoelectric, electromagnetic, electrodynamic, thermal, induction, detector, thermoelectric and photoelectric. Magnetoelectric ammeters measure direct current; induction and detector - alternating current; ammeters of other systems measure the strength of any current. The most accurate and sensitive are magnetoelectric and electrodynamic ammeters.
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Manual spring scales Manual spring scales are a hand-held device for measuring weight or mass, a hand-held dynamometer. Typically intended for domestic use. They are a fairly stiff spring that fits into a housing with a scale. An arrow is attached to the spring. As long as no force is applied to the spring, that is, the load being measured is not suspended, it is in a compressed state. Under the influence of gravity, the spring stretches and moves accordingly along the arrow scale. Based on the position of the arrow, you can find out the mass of the load being weighed. Spring ones can be equipped with an additional system of rotating gears, which allows you to measure the mass of objects even more accurately. The latest models of household scales are made electronic. Sometimes manual spring scales are also called steelyard
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Thermometer Thermo meter (Greek θέρμη - heat and μετρέω - I measure) - a device for measuring the temperature of air, soil, water, and so on. There are several types of thermometers: Liquid, electric, optical, gas.
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History of the invention Galileo is considered to be the inventor of the thermometer: there is no description of this device in his own writings, but his students, Nelli and Viviani, testified that already in 1597 he created something like a thermobaroscope. Galileo was studying at this time Heron of Alexandria, who had already described a similar device, but not for measuring degrees of heat, but for raising water by heating. The invention of the thermometer is also attributed to Lord Bacon, Robert Fludd, Sanctorius, Scarpi, Cornelius Drebbel, Porte and Salomon de Caus, who wrote later and partly had personal relations with Galileo. All these thermometers were air thermometers and consisted of a vessel with a tube containing air separated from the atmosphere by a column of water; they changed their readings both from changes in temperature and from changes in atmospheric pressure. Thermometers with liquid were described for the first time in 1667 “Saggi di naturale esperienze fatte nell'Accademia del Cimento”, where they are described as objects that have long been made by skilled artisans, called “Confia”, who heat the glass on the blown fire of a lamp and making amazing and very delicate products from it. At first these thermometers were filled with water, and they burst when it froze; The use of wine alcohol for this purpose began at the thought of the Grand Duke of Tuscany Ferdinand II. The Florentine thermometers are not only depicted in “Saggi”, but have been preserved in several copies to this day in the Galilean Museum, in Florence; their preparation is described in detail. First, the master had to make divisions on the tube, taking into account the relative sizes of it and the ball: the divisions were applied with molten enamel onto the tube heated in a lamp, every tenth was indicated by a white dot, and the others by black. They usually made 50 divisions so that when the snow melts, the alcohol does not drop below 10, and in the sun does not rise above 40. Good craftsmen made such thermometers so successfully that all thermometers showed the same thing under the same conditions, but no one managed to achieve this , if the tube was divided into 100 or 300 parts to obtain greater sensitivity. The thermometers were filled by heating the ball and lowering the end of the tube into alcohol, but the filling was completed using a glass funnel with a thin end that fit freely into a fairly wide tube. After adjusting the amount of liquid, the opening of the tube was sealed with sealing wax, called "sealant". From this it is clear that these thermometers were large and could be used to determine air temperature, but they were still inconvenient for other, more diverse experiments, and the degrees of different thermometers were not comparable with each other. In 1703, Guillaume Amontons in Paris improved the air thermometer, measuring not the expansion, but the increase in elasticity of air reduced to the same volume at different temperatures by pouring mercury into an open elbow; barometric pressure and its changes were taken into account. The zero of such a scale was supposed to be “that significant degree of cold” at which the air loses all its elasticity (that is, modern absolute zero), and the second constant point was the boiling point of water. The effect of atmospheric pressure on the boiling point was not yet known to Amonton, and the air in his thermometer was not freed from water gases; therefore, from his data, absolute zero is obtained at 239.5 ° centigrade modern scale. Another air thermometer of Amonton, very imperfectly made, was independent of changes in atmospheric pressure: it was a siphon barometer, the open elbow of which was extended upward, filled first with a strong solution of potash, with oil on top and ending in a sealed reservoir with air. Fahrenheit gave the thermometer its modern form and described his method of preparation in 1723. Initially, he also filled his tubes with alcohol and only finally switched to mercury. He set the zero of his scale at the temperature of a mixture of snow with ammonia or table salt, but at the temperature of “beginning freezing of water” he set it at 32°, and at 96° at the temperature of a healthy human body, in the mouth or under the armpit. Subsequently, he found that water boils at 212° and this temperature was always the same at the same barometer. The Swedish physicist Celsius finally established both constant points, melting ice and boiling water, in 1742, but initially he put 0° at the boiling point, and 100° at the freezing point, and adopted the reverse designation only on the advice of M. Störmer. Surviving examples of Fahrenheit thermometers are distinguished by their meticulous execution. Reaumur's work in 1736, although it led to the establishment of an 80° scale, was rather a step back against what Fahrenheit had already done: Reaumur's thermometer was huge, inconvenient to use, and its method of dividing into degrees was inaccurate and inconvenient. After Fahrenheit and Reaumur, the business of making thermometers fell into the hands of artisans, as thermometers became an item of trade. Galileo is considered to be the inventor of the thermometer: in his own writings there is no description of this device, but his students, Nelli and Viviani, testified that already in 1597 he created something like a thermobaroscope. Galileo was studying at this time Heron of Alexandria, who had already described a similar device, but not for measuring degrees of heat, but for raising water by heating. The invention of the thermometer is also attributed to Lord Bacon, Robert Fludd, Sanctorius, Scarpi, Cornelius Drebbel, Porte and Salomon de Caus, who wrote later and partly had personal relations with Galileo. All these thermometers were air thermometers and consisted of a vessel with a tube containing air separated from the atmosphere by a column of water; they changed their readings both from changes in temperature and from changes in atmospheric pressure. First, the master had to make divisions on the tube, taking into account the relative sizes of it and the ball: the divisions were applied with molten enamel onto the tube heated in a lamp, every tenth was indicated by a white dot, and the others by black. They usually made 50 divisions so that when the snow melts, the alcohol does not drop below 10, and in the sun does not rise above 40. Good craftsmen made such thermometers so successfully that all thermometers showed the same thing under the same conditions, but no one managed to achieve this , if the tube was divided into 100 or 300 parts to obtain greater sensitivity. The thermometers were filled by heating the ball and lowering the end of the tube into alcohol, but the filling was completed using a glass funnel with a thin end that fit freely into a fairly wide tube. After adjusting the amount of liquid, the opening of the tube was sealed with sealing wax, called "sealant".
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A dosimeter is a device for measuring the dose or dose rate of ionizing radiation received by the device (and by those who use it) over a certain period of time, for example, during a period of stay in a certain area or during a work shift. The measurement of the above quantities is called dosimetry. Sometimes a “dosimeter” is not quite accurately called a radiometer - a device for measuring the activity of a radionuclide in a source or sample (in a volume of liquid, gas, aerosol, on contaminated surfaces) or the flux density of ionizing radiation to test suspicious objects for radioactivity and assess the radiation situation in a given place At the moment. The measurement of the quantities described above is called radiometry. An X-ray meter is a type of radiometer for measuring the power of gamma radiation.
“Electric current in various media” - Electric current in gases. Electric current in semiconductors. Faraday's law. Lesson in 8th grade. Semiconductor diodes, transistors. Independent gas discharges: spark, arc, corona, glow. One-way conduction at the interface of n-type p-type semiconductors. N-type semiconductors, p-type semiconductors. Electric current in a vacuum. Electric current in metals. Electrotype. Vacuum diodes.
“Turbine and internal combustion engine” - An internal combustion engine is a very common type of heat engine. Powerful internal combustion engines are installed on river and sea vessels. One stroke of the piston is completed per half revolution of the crankshaft. Internal combustion engine. ICE cycle. The third stroke of the internal combustion engine. Therefore, such engines are called four-stroke. 1. Disk 2. Shaft 3. Blades 4. Nozzle.
“Laws of DC” - Make up a story based on the pictures. Laboratory work. Study of the structure of a galvanic cell. R. in Koenigsberg. The motors are asynchronous with a squirrel-cage rotor. III1824 – 17.X1887) - German physicist, member of the Berlin Academy of Sciences (1875). Personal goals. Home experiment. "Investigation of series connection of conductors." Content. Historical reference.
“Ways to change internal energy” - Ways to change the internal energy of the body. 1.What movement is called thermal? Physics lesson in 8th grade. T? ? v molecules?. Dependence of internal energy of a body on body temperature. T? ? v molecules?. Dependence of the speed of movement of molecules on body temperature. 3. What energy is called internal? En depends on the distance between molecules (the state of aggregation of the substance).
“Physics in the bathroom” - Don’t similar troubles happen with cold water? Problems: Heat is required to evaporate water. Completed by: Rocheva Anzhelika Semyashkina Elena Pupils 8 “c”. Why is your voice louder in the bathroom? Why is your voice louder in the bathroom? Goal: How to measure your body volume? Why do the walls and mirrors fog up when you wash in the shower?
“Mechanical waves grade 9” - Wave length, ?: ? =v? T or? = v: ? [?] = m. What is the wavelength? ENERGY. Mechanical waves -. Physics 9th grade. Explain the situation: The source oscillates along the OY axis perpendicular to OX. What "moves" in the wave? The source oscillates along the OX axis. The mechanism of oscillations. First there's a shine, after the shine there's a crackle, after the crackle there's a splash. Elastic medium model. B. Energy.
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What it is?
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Device
- An instrument is a device for measuring physical quantities.
- It was called measuring because it is used to measure something.
- To measure means to compare one quantity with another.
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- Each device has a scale (division). The values are compared using it.
- Let's take the simplest device - a ruler and consider it. It is straight and has a scale.
- The scale of the ruler is not simple; it contains two physical quantities, centimeter and millimeter. So a five-centimeter ruler has
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- Fifty short lines, one mm each, spaced apart from each other (this is approximately equal to the thickness of the wire of a mesh fence) and five long lines, one cm each (this is approximately equal to the width of the little fingernail).
- That means 1cm is 10mm. Only centimeters are signed. Because millimeters are inconvenient to use.
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Purpose
- So the ruler has two purposes:
- 1) drawing straight lines and checking the lines (whether they are straight).
- 2)measuring the length of objects
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Dynamometer
- A dynamometer is a device for measuring force.
- The price of one division is equal to one Newton. (written 1N)
- A dynamometer can measure friction force and traction force.
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Types of dynamometers
- Medical dynamometer (for measuring the strength of different human muscle groups)
- Hand-held dynamometer-silometer. (to measure arm strength)
- Traction dynamometer. (for measuring large forces)
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Athletes use this device
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Silomer
- The strength meter consists of two oval handles connected by a spring
- When they are compressed, the metal plate transmits the action to the arrow. The price of one division is 1 kg.
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With this device you can predict the weather
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Aneroid barometer
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Barometer
- A barometer is a metal instrument for measuring atmospheric pressure.
- The price of one division is equal to two mm Hg. Art.
- Its structure is similar to a monometer.
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Aneroid barometer
- Structure: this is a metal box from which air has been pumped out. A spring is attached to it so that it does not get crushed by atmospheric pressure. The spring is attached to the arrow using an additional mechanism.
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Why not measure tire pressure?
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Pressure gauge
- A pressure gauge is used to measure pressure greater or less than atmospheric pressure.
- One division of the pressure gauge is the atmosphere.
- 2 atmospheres means that the pressure is greater than atm. 2 times.
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- The device works due to elasticity.
- Structure: this is a curved metal tube sealed on one side. It is attached to the arrow using a toothed gear. If the pressure increases
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- - is lit, then the tube straightens and gives movement to the arrow. She starts moving to the right. If the pressure decreases, the tube bends back (due to elasticity) until it takes its original shape. The arrow continues to move behind the tube constantly.