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| quantitative | forces |
| physical | scale |
| metric | measure |
| equal arm | deflection |
| gravitational | quantity |
| weighing | point |
| spring | balance |
| angular | device |
| pivot | system |
Answer the following questions.
1. What is the difference between mass and weight?
2. What is the unit for mass according to SI?
3. What is the unit for mass in the USA?
4. Name all weighing instruments mentioned in the text.
5. What was the first instrument used for weighing?
6. What measuring instrument is used to determine the mass of an object by measuring the force exerted by the object on its support within the gravitation field of the earth?
7. Is substitution balance similar to an equal arm balance?
8. What is the least expensive device for making mass measurements?
9. Name two kinds of spring scales.
10. What device is used to determine the mass indirectly?
11. What is the difference between beam balance and equal arm balance?
12. What is the disadvantage of beam balance?
Complete the sentences using the text A.
1. Weight force is determined by… .
2. The equal arm balance is a simple device in which… .
3. In spring scales capacity can be increased by … .
4. The torsion element in torsion balance could be … .
5. Large beam scales are made with capacities … .
Suggest the title to the text.
What new information did you get from the text? Discuss in a group.
Find in the text English equivalents to the following Ukrainian words and word combinations. Then make your own sentences with each one.
заміна, заміщення – s _ _ _ _ _ _ _ _ _ n
скручування, перекручування – t _ _ _ _ _n
обертальний момент – t _ _ _ _ e
сила тяжіння – g _ _ _ _ _ y
пружина – s _ _ _ _ g
консольний, звисаючий – c _ _ _ _ _ _ _ _ _ _ d
кількісний – q _ _ _ _ _ _ _ _ _ _ e
поєднання, інтеграція – e _ _ _ _ _ _ _ _ t
визначати, означати – d _ _ _ _ _ _ _ e
відхилення – d_ _ _ _ _ _ _ _ n
зміщений, відхилений – o _ _ _ _ t
зазублений, вищерблений – n _ _ _ _ _ d
ручка, рукоятка – _ _ m
точка повороту – p _ _ _ _ p _ _ _ _
лоток, піддон – _ _ n
балка, брус, ствол – b _ _ _
датчик навантаження – l _ _ _ c_ _ _
Give comparative and superlative forms of adjectives.
Often, old, simple, short, expensive, small, accurate, new, important, reliable, efficient, consistent, robust, humid, fatigue, resistant.
Define the function of the Present and Past Participle in the following sentences and translate them into Ukrainian.
1. Weighing is one of the oldest known measurements, dating back to before written history
2. The equal arm balance was probably the first instrument used for weighing.
3. By adding up the forces indicated by the position of each weight, the mass of the unknown material is determined.
4. Along the beam, there are notched positions that are marked to correspond to the force applied by the sliding weights
5. Capacity can be increased by increasing the strength of the spring
6. A balance is a measuring instrument used to determine the mass of an object by measuring the force exerted by the object on its support within the gravitational field of the Earth
7. Given the short distance between pans, one assumes that the gravitational forces acting on them are equal.
8. In the International System of Units, the modernized metric measurement system, the unit for mass is called the kilogram and the unit for force is called the Newton.
9. The first standards (étalons) of the metre and the kilogram were deposited in the Archives of the French Republic in 1799, dedicated to "all men and all times".
10. The torsion balance is a precise adaptation of the spring concept used to determine the mass indirectly
11. Adopted at the start of the 19th century in several Italian provinces, the metric system became compulsory in the Netherlands from 1816 and was chosen by Spain in 1849
12. By measuring the resistance of the strain gage, it is possible to determine the load on the load cell.
13. Attached to the beam is a null indicating device, consisting of a photodiode and a light-emitting diode (LED) that are used to determine when the balance is in equilibrium
14. Depending on the application, synchronization errors may or may not be important.
15. These weighing devices are employing the electromagnetic force compensation principle in conjunction with joint flexures elements replacing the traditional knife-edge joints.
Read and translate text B.
TEXT B
The next progression in cost and accuracy is the strain gage load cell. A strain gage is an electrically resistive wire element that changes resistance when the length of the wire element changes. The gage is bonded to a steel cylinder that will shorten when compressed or lengthen when stretched. Because the gage is bonded to the cylinder, the length of the wire will lengthen or contract with the cylinder. The electrical resistance is proportional to the length of the wire element of the gage. By measuring the resistance of the strain gage, it is possible to determine the load on the load cell. The electric resistance is converted into a mass unit readout by the electric circuitry in the readout device.
The force restorative load cell is the heart of an electronic balance. The force restorative load cell uses the principle of the equal arm balance. However, in most cases, the fulcrum is offset so it is no longer an equal arm balance, as one side is designed to have a mechanical advantage. This side of the balance is attached to an electric coil. The coil is suspended in a magnetic field. The other side is still connected to a weighing pan. Attached to the beam is a null indicating device, consisting of a photodiode and a light-emitting diode (LED) that are used to determine when the balance is in equilibrium. When a load is placed on the weighing pan, the balance goes out of equilibrium. The LED photodiode circuit detects that the balance is no longer in equilibrium, and the electric current in the coil is increased to bring the balance back to equilibrium. The electric current is then measured across a precision sense resistor and converted into a mass unit reading and displayed on the digital readout.
A variation of the latter is the new generation of industrial scales, laboratory balances, and mass comparators. Mass comparators are no longer called balances because they always perform a comparison between known masses (standards) and unknown masses. These weighing devices are employing the electromagnetic force compensation principle in conjunction with joint flexures elements replacing the traditional knife-edge joints. Some of the advantages include a computer interfacing capability and a maintenance-free feature because there are no moving parts.
Another measuring method used in the weighing technology is the vibrating cord. A wire or cord of known length, which vibrates transversely, is tensioned by the force F . The vibration frequency changes in direct proportion to the load F. The piezoelectric effect is also used in weighing technology. Such weighing devices consist of the presence of an electric voltage at the surface of a crystal when the crystal is under load. Balances employing the gyroscopic effect are also used. This measuring device uses the output signal of a gyrodynamic cell similar to the frequency. Balances wherein the weight force of the load changes the reference distance of the capacitive or inductive converters are also known. As well, balances using the radioactivity changes of a body as a function of its mass under certain conditions exist.
Дата: 2016-10-02, просмотров: 184.